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1 .TH LIBPNG 3 "September 18, 2008" |
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2 .SH NAME |
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3 libpng \- Portable Network Graphics (PNG) Reference Library 1.2.32 |
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4 .SH SYNOPSIS |
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5 \fI\fB |
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6 |
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7 \fB#include <png.h>\fP |
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8 |
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9 \fI\fB |
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10 |
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11 \fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP |
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12 |
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13 \fI\fB |
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14 |
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15 \fBint png_check_sig (png_bytep \fP\fIsig\fP\fB, int \fInum\fP\fB);\fP |
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16 |
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17 \fI\fB |
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18 |
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19 \fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
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20 |
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21 \fI\fB |
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22 |
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23 \fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP |
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24 |
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25 \fI\fB |
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26 |
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27 \fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP |
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28 |
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29 \fI\fB |
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30 |
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31 \fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP |
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32 |
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33 \fI\fB |
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34 |
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35 \fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP |
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36 |
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37 \fI\fB |
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38 |
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39 \fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP |
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40 |
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41 \fI\fB |
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42 |
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43 \fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP |
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44 |
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45 \fI\fB |
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46 |
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47 \fBpng_structp png_create_read_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
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48 |
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49 \fI\fB |
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50 |
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51 \fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP |
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52 |
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53 \fI\fB |
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54 |
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55 \fBpng_structp png_create_write_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
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56 |
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57 \fI\fB |
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58 |
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59 \fBint png_debug(int \fP\fIlevel\fP\fB, png_const_charp \fImessage\fP\fB);\fP |
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60 |
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61 \fI\fB |
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62 |
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63 \fBint png_debug1(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fIp1\fP\fB);\fP |
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64 |
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65 \fI\fB |
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66 |
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67 \fBint png_debug2(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fP\fIp1\fP\fB, \fIp2\fP\fB);\fP |
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68 |
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69 \fI\fB |
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70 |
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71 \fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP |
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72 |
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73 \fI\fB |
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74 |
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75 \fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP |
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76 |
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77 \fI\fB |
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78 |
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79 \fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP |
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80 |
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81 \fI\fB |
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82 |
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83 \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
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84 |
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85 \fI\fB |
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86 |
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87 \fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP |
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88 |
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89 \fI\fB |
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90 |
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91 \fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP |
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92 |
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93 \fI\fB |
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94 |
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95 \fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP |
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96 |
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97 \fI\fB |
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98 |
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99 \fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP |
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100 |
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101 \fI\fB |
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102 |
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103 \fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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104 |
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105 \fI\fB |
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106 |
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107 \fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP |
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108 |
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109 \fI\fB |
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110 |
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111 \fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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112 |
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113 \fI\fB |
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114 |
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115 \fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP |
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116 |
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117 \fI\fB |
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118 |
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119 \fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP |
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120 |
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121 \fI\fB |
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122 |
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123 \fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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124 |
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125 \fI\fB |
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126 |
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127 \fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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128 |
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129 \fI\fB |
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130 |
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131 \fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP |
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132 |
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133 \fI\fB |
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134 |
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135 \fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
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136 |
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137 \fI\fB |
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138 |
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139 \fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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140 |
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141 \fI\fB |
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142 |
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143 \fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP |
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144 |
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145 \fI\fB |
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146 |
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147 \fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP |
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148 |
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149 \fI\fB |
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150 |
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151 \fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP |
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152 |
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153 \fI\fB |
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154 |
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155 \fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP |
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156 |
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157 \fI\fB |
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158 |
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159 \fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP |
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160 |
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161 \fI\fB |
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162 |
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163 \fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP |
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164 |
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165 \fI\fB |
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166 |
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167 \fBpng_uint_32 png_get_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*width\fP\fB, png_uint_32 \fP\fI*height\fP\fB, int \fP\fI*bit_depth\fP\fB, int \fP\fI*color_type\fP\fB, int \fP\fI*interlace_type\fP\fB, int \fP\fI*compression_type\fP\fB, int \fI*filter_type\fP\fB);\fP |
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168 |
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169 \fI\fB |
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170 |
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171 \fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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172 |
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173 \fI\fB |
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174 |
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175 \fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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176 |
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177 \fI\fB |
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178 |
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179 \fB#if \fI!defined(PNG_1_0_X) |
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180 |
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181 \fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP |
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182 |
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183 \fI\fB#endif |
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184 |
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185 \fI\fB |
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186 |
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187 \fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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188 |
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189 \fI\fB |
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190 |
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191 \fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
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192 |
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193 \fI\fB |
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194 |
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195 \fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP |
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196 |
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197 \fI\fB |
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198 |
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199 \fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP |
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200 |
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201 \fI\fB |
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202 |
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203 \fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP |
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204 |
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205 \fI\fB |
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206 |
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207 \fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP |
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208 |
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209 \fI\fB |
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210 |
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211 \fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP |
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212 |
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213 \fI\fB |
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214 |
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215 \fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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216 |
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217 \fI\fB |
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218 |
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219 \fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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220 |
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221 \fI\fB |
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222 |
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223 \fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
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224 |
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225 \fI\fB |
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226 |
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227 \fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP |
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228 |
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229 \fI\fB |
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230 |
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231 \fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr) |
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232 |
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233 \fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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234 |
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235 \fI\fB |
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236 |
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237 \fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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238 |
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239 \fI\fB |
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240 |
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241 \fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP |
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242 |
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243 \fI\fB |
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244 |
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245 \fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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246 |
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247 \fI\fB |
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248 |
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249 \fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP |
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250 |
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251 \fI\fB |
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252 |
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253 \fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP |
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254 |
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255 \fI\fB |
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256 |
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257 \fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP |
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258 |
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259 \fI\fB |
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260 |
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261 \fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP |
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262 |
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263 \fI\fB |
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264 |
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265 \fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_values\fP\fB);\fP |
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266 |
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267 \fI\fB |
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268 |
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269 \fB#if \fI!defined(PNG_1_0_X) |
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270 |
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271 \fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP |
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272 |
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273 \fI\fB |
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274 |
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275 \fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP |
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276 |
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277 \fI\fB |
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278 |
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279 \fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP |
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280 |
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281 \fI\fB#endif |
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282 |
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283 \fI\fB |
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284 |
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285 \fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP |
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286 |
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287 \fI\fB |
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288 |
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289 \fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
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290 |
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291 \fI\fB |
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292 |
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293 \fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP |
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294 |
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295 \fI\fB |
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296 |
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297 \fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
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298 |
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299 \fI\fB |
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300 |
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301 \fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP |
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302 |
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303 \fI\fB |
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304 |
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305 \fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP |
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306 |
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307 \fI\fB |
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308 |
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309 \fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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310 |
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311 \fI\fB |
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312 |
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313 \fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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314 |
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315 \fI\fB |
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316 |
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317 \fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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318 |
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319 \fI\fB |
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320 |
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321 \fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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322 |
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323 \fI\fB |
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324 |
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325 \fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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326 |
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327 \fI\fB |
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328 |
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329 \fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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330 |
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331 \fI\fB |
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332 |
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333 \fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP |
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334 |
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335 \fI\fB |
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336 |
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337 \fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP |
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338 |
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339 \fI\fB |
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340 |
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341 \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP |
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342 |
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343 \fI\fB |
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344 |
|
345 \fBDEPRECATED: void png_info_init (png_infop \fIinfo_ptr\fP\fB);\fP |
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346 |
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347 \fI\fB |
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348 |
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349 \fBDEPRECATED: void png_info_init_2 (png_infopp \fP\fIptr_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP |
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350 |
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351 \fI\fB |
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352 |
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353 \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
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354 |
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355 \fI\fB |
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356 |
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357 \fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
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358 |
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359 \fI\fB |
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360 |
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361 \fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP |
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362 |
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363 \fI\fB |
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364 |
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365 \fBpng_voidp png_memcpy_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
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366 |
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367 \fI\fB |
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368 |
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369 \fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP |
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370 |
|
371 \fI\fB |
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372 |
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373 \fBpng_voidp png_memset_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
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374 |
|
375 \fI\fB |
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376 |
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377 \fBDEPRECATED: void png_permit_empty_plte (png_structp \fP\fIpng_ptr\fP\fB, int \fIempty_plte_permitted\fP\fB);\fP |
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378 |
|
379 \fI\fB |
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380 |
|
381 \fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, png_size_t \fIbuffer_size\fP\fB);\fP |
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382 |
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383 \fI\fB |
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384 |
|
385 \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP |
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386 |
|
387 \fI\fB |
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388 |
|
389 \fBvoid png_read_destroy (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_infop \fIend_info_ptr\fP\fB);\fP |
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390 |
|
391 \fI\fB |
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392 |
|
393 \fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
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394 |
|
395 \fI\fB |
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396 |
|
397 \fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP |
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398 |
|
399 \fI\fB |
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400 |
|
401 \fBDEPRECATED: void png_read_init (png_structp \fIpng_ptr\fP\fB);\fP |
|
402 |
|
403 \fI\fB |
|
404 |
|
405 \fBDEPRECATED: void png_read_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP |
|
406 |
|
407 \fI\fB |
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408 |
|
409 \fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
|
410 |
|
411 \fI\fB |
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412 |
|
413 \fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP |
|
414 |
|
415 \fI\fB |
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416 |
|
417 \fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP |
|
418 |
|
419 \fI\fB |
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420 |
|
421 \fBvoid png_read_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_bytepp \fP\fIdisplay_row\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP |
|
422 |
|
423 \fI\fB |
|
424 |
|
425 \fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
|
426 |
|
427 \fI\fB |
|
428 |
|
429 \fB#if \fI!defined(PNG_1_0_X) |
|
430 |
|
431 \fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP |
|
432 |
|
433 \fI\fB |
|
434 |
|
435 \fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP |
|
436 |
|
437 \fI\fB |
|
438 |
|
439 \fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP |
|
440 |
|
441 \fI\fB |
|
442 |
|
443 \fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP |
|
444 |
|
445 \fI\fB#endif |
|
446 |
|
447 \fI\fB |
|
448 |
|
449 \fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP |
|
450 |
|
451 \fI\fB |
|
452 |
|
453 \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP |
|
454 |
|
455 \fI\fB |
|
456 |
|
457 \fBvoid png_set_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fIbackground\fP\fB);\fP |
|
458 |
|
459 \fI\fB |
|
460 |
|
461 \fBvoid png_set_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP |
|
462 |
|
463 \fI\fB |
|
464 |
|
465 \fBvoid png_set_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwhite_x\fP\fB, png_uint_32 \fP\fIwhite_y\fP\fB, png_uint_32 \fP\fIred_x\fP\fB, png_uint_32 \fP\fIred_y\fP\fB, png_uint_32 \fP\fIgreen_x\fP\fB, png_uint_32 \fP\fIgreen_y\fP\fB, png_uint_32 \fP\fIblue_x\fP\fB, png_uint_32 \fIblue_y\fP\fB);\fP |
|
466 |
|
467 \fI\fB |
|
468 |
|
469 \fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP |
|
470 |
|
471 \fI\fB |
|
472 |
|
473 \fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP |
|
474 |
|
475 \fI\fB |
|
476 |
|
477 \fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP |
|
478 |
|
479 \fI\fB |
|
480 |
|
481 \fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP |
|
482 |
|
483 \fI\fB |
|
484 |
|
485 \fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP |
|
486 |
|
487 \fI\fB |
|
488 |
|
489 \fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP |
|
490 |
|
491 \fI\fB |
|
492 |
|
493 \fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP |
|
494 |
|
495 \fI\fB |
|
496 |
|
497 \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP |
|
498 |
|
499 \fI\fB |
|
500 |
|
501 \fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP |
|
502 |
|
503 \fI\fB |
|
504 |
|
505 \fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP |
|
506 |
|
507 \fI\fB |
|
508 |
|
509 \fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP |
|
510 |
|
511 \fI\fB |
|
512 |
|
513 \fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP |
|
514 |
|
515 \fI\fB |
|
516 |
|
517 \fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP |
|
518 |
|
519 \fI\fB |
|
520 |
|
521 \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP |
|
522 |
|
523 \fI\fB |
|
524 |
|
525 \fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP |
|
526 |
|
527 \fI\fB |
|
528 |
|
529 \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP |
|
530 |
|
531 \fI\fB |
|
532 |
|
533 \fBvoid png_set_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIfile_gamma\fP\fB);\fP |
|
534 |
|
535 \fI\fB |
|
536 |
|
537 \fBvoid png_set_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP |
|
538 |
|
539 \fI\fB |
|
540 |
|
541 \fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP |
|
542 |
|
543 \fI\fB |
|
544 |
|
545 \fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP |
|
546 |
|
547 \fI\fB |
|
548 |
|
549 \fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP |
|
550 |
|
551 \fI\fB |
|
552 |
|
553 \fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP |
|
554 |
|
555 \fI\fB |
|
556 |
|
557 \fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP |
|
558 |
|
559 \fI\fB |
|
560 |
|
561 \fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
|
562 |
|
563 \fI\fB |
|
564 |
|
565 \fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP |
|
566 |
|
567 \fI\fB |
|
568 |
|
569 \fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP |
|
570 |
|
571 \fI\fB |
|
572 |
|
573 \fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP |
|
574 |
|
575 \fI\fB |
|
576 |
|
577 \fBvoid png_set_mem_fn(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
|
578 |
|
579 \fI\fB |
|
580 |
|
581 \fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP |
|
582 |
|
583 \fI\fB |
|
584 |
|
585 \fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP |
|
586 |
|
587 \fI\fB |
|
588 |
|
589 \fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP |
|
590 |
|
591 \fI\fB |
|
592 |
|
593 \fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP |
|
594 |
|
595 \fI\fB |
|
596 |
|
597 \fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP |
|
598 |
|
599 \fI\fB |
|
600 |
|
601 \fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP |
|
602 |
|
603 \fI\fB |
|
604 |
|
605 \fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP |
|
606 |
|
607 \fI\fB |
|
608 |
|
609 \fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP |
|
610 |
|
611 \fI\fB |
|
612 |
|
613 \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP |
|
614 |
|
615 \fI\fB |
|
616 |
|
617 \fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP |
|
618 |
|
619 \fI\fB |
|
620 |
|
621 \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP |
|
622 |
|
623 \fI\fB |
|
624 |
|
625 \fBvoid png_set_rgb_to_gray (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIerror_action\fP\fB, double \fP\fIred\fP\fB, double \fIgreen\fP\fB);\fP |
|
626 |
|
627 \fI\fB |
|
628 |
|
629 \fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP |
|
630 |
|
631 \fI\fB |
|
632 |
|
633 \fBvoid png_set_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytepp \fIrow_pointers\fP\fB);\fP |
|
634 |
|
635 \fI\fB |
|
636 |
|
637 \fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP |
|
638 |
|
639 \fI\fB |
|
640 |
|
641 \fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP |
|
642 |
|
643 \fI\fB |
|
644 |
|
645 \fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP |
|
646 |
|
647 \fI\fB |
|
648 |
|
649 \fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP |
|
650 |
|
651 \fI\fB |
|
652 |
|
653 \fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP |
|
654 |
|
655 \fI\fB |
|
656 |
|
657 \fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP |
|
658 |
|
659 \fI\fB |
|
660 |
|
661 \fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP |
|
662 |
|
663 \fI\fB |
|
664 |
|
665 \fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP |
|
666 |
|
667 \fI\fB |
|
668 |
|
669 \fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
|
670 |
|
671 \fI\fB |
|
672 |
|
673 \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP |
|
674 |
|
675 \fI\fB |
|
676 |
|
677 \fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
|
678 |
|
679 \fI\fB |
|
680 |
|
681 \fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP |
|
682 |
|
683 \fI\fB |
|
684 |
|
685 \fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP |
|
686 |
|
687 \fI\fB |
|
688 |
|
689 \fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_values\fP\fB);\fP |
|
690 |
|
691 \fI\fB |
|
692 |
|
693 \fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP |
|
694 |
|
695 \fI\fB |
|
696 |
|
697 \fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP |
|
698 |
|
699 \fI\fB |
|
700 |
|
701 \fBvoid png_set_unknown_chunk_location(png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP |
|
702 |
|
703 \fI\fB |
|
704 |
|
705 \fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP |
|
706 |
|
707 \fI\fB |
|
708 |
|
709 \fBvoid png_set_user_limits (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIuser_width_max\fP\fB, png_uint_32 \fIuser_height_max\fP\fB);\fP |
|
710 |
|
711 \fI\fB |
|
712 |
|
713 \fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP |
|
714 |
|
715 \fI\fB |
|
716 |
|
717 \fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP |
|
718 |
|
719 \fI\fB |
|
720 |
|
721 \fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP |
|
722 |
|
723 \fI\fB |
|
724 |
|
725 \fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP |
|
726 |
|
727 \fI\fB |
|
728 |
|
729 \fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
|
730 |
|
731 \fI\fB |
|
732 |
|
733 \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP |
|
734 |
|
735 \fI\fB |
|
736 |
|
737 \fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP |
|
738 |
|
739 \fI\fB |
|
740 |
|
741 \fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP |
|
742 |
|
743 \fI\fB |
|
744 |
|
745 \fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP |
|
746 |
|
747 \fI\fB |
|
748 |
|
749 \fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP |
|
750 |
|
751 \fI\fB |
|
752 |
|
753 \fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP |
|
754 |
|
755 \fI\fB |
|
756 |
|
757 \fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP |
|
758 |
|
759 \fI\fB |
|
760 |
|
761 \fBvoid png_write_destroy (png_structp \fIpng_ptr\fP\fB);\fP |
|
762 |
|
763 \fI\fB |
|
764 |
|
765 \fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
|
766 |
|
767 \fI\fB |
|
768 |
|
769 \fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP |
|
770 |
|
771 \fI\fB |
|
772 |
|
773 \fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP |
|
774 |
|
775 \fI\fB |
|
776 |
|
777 \fBDEPRECATED: void png_write_init (png_structp \fIpng_ptr\fP\fB);\fP |
|
778 |
|
779 \fI\fB |
|
780 |
|
781 \fBDEPRECATED: void png_write_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP |
|
782 |
|
783 \fI\fB |
|
784 |
|
785 \fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
|
786 |
|
787 \fI\fB |
|
788 |
|
789 \fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
|
790 |
|
791 \fI\fB |
|
792 |
|
793 \fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP |
|
794 |
|
795 \fI\fB |
|
796 |
|
797 \fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP |
|
798 |
|
799 \fI\fB |
|
800 |
|
801 \fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP |
|
802 |
|
803 \fI\fB |
|
804 |
|
805 \fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP |
|
806 |
|
807 \fI\fB |
|
808 |
|
809 \fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP |
|
810 |
|
811 \fI\fB |
|
812 |
|
813 .SH DESCRIPTION |
|
814 The |
|
815 .I libpng |
|
816 library supports encoding, decoding, and various manipulations of |
|
817 the Portable Network Graphics (PNG) format image files. It uses the |
|
818 .IR zlib(3) |
|
819 compression library. |
|
820 Following is a copy of the libpng.txt file that accompanies libpng. |
|
821 .SH LIBPNG.TXT |
|
822 libpng.txt - A description on how to use and modify libpng |
|
823 |
|
824 libpng version 1.2.32 - September 18, 2008 |
|
825 Updated and distributed by Glenn Randers-Pehrson |
|
826 <glennrp at users.sourceforge.net> |
|
827 Copyright (c) 1998-2008 Glenn Randers-Pehrson |
|
828 For conditions of distribution and use, see copyright |
|
829 notice in png.h. |
|
830 |
|
831 Based on: |
|
832 |
|
833 libpng versions 0.97, January 1998, through 1.2.32 - September 18, 2008 |
|
834 Updated and distributed by Glenn Randers-Pehrson |
|
835 Copyright (c) 1998-2008 Glenn Randers-Pehrson |
|
836 |
|
837 libpng 1.0 beta 6 version 0.96 May 28, 1997 |
|
838 Updated and distributed by Andreas Dilger |
|
839 Copyright (c) 1996, 1997 Andreas Dilger |
|
840 |
|
841 libpng 1.0 beta 2 - version 0.88 January 26, 1996 |
|
842 For conditions of distribution and use, see copyright |
|
843 notice in png.h. Copyright (c) 1995, 1996 Guy Eric |
|
844 Schalnat, Group 42, Inc. |
|
845 |
|
846 Updated/rewritten per request in the libpng FAQ |
|
847 Copyright (c) 1995, 1996 Frank J. T. Wojcik |
|
848 December 18, 1995 & January 20, 1996 |
|
849 |
|
850 .SH I. Introduction |
|
851 |
|
852 This file describes how to use and modify the PNG reference library |
|
853 (known as libpng) for your own use. There are five sections to this |
|
854 file: introduction, structures, reading, writing, and modification and |
|
855 configuration notes for various special platforms. In addition to this |
|
856 file, example.c is a good starting point for using the library, as |
|
857 it is heavily commented and should include everything most people |
|
858 will need. We assume that libpng is already installed; see the |
|
859 INSTALL file for instructions on how to install libpng. |
|
860 |
|
861 For examples of libpng usage, see the files "example.c", "pngtest.c", |
|
862 and the files in the "contrib" directory, all of which are included in the |
|
863 libpng distribution. |
|
864 |
|
865 Libpng was written as a companion to the PNG specification, as a way |
|
866 of reducing the amount of time and effort it takes to support the PNG |
|
867 file format in application programs. |
|
868 |
|
869 The PNG specification (second edition), November 2003, is available as |
|
870 a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at |
|
871 <http://www.w3.org/TR/2003/REC-PNG-20031110/ |
|
872 The W3C and ISO documents have identical technical content. |
|
873 |
|
874 The PNG-1.2 specification is available at |
|
875 <http://www.libpng.org/pub/png/documents/>. It is technically equivalent |
|
876 to the PNG specification (second edition) but has some additional material. |
|
877 |
|
878 The PNG-1.0 specification is available |
|
879 as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a |
|
880 W3C Recommendation <http://www.w3.org/TR/REC.png.html>. |
|
881 |
|
882 Some additional chunks are described in the special-purpose public chunks |
|
883 documents at <http://www.libpng.org/pub/png/documents/>. |
|
884 |
|
885 Other information |
|
886 about PNG, and the latest version of libpng, can be found at the PNG home |
|
887 page, <http://www.libpng.org/pub/png/>. |
|
888 |
|
889 Most users will not have to modify the library significantly; advanced |
|
890 users may want to modify it more. All attempts were made to make it as |
|
891 complete as possible, while keeping the code easy to understand. |
|
892 Currently, this library only supports C. Support for other languages |
|
893 is being considered. |
|
894 |
|
895 Libpng has been designed to handle multiple sessions at one time, |
|
896 to be easily modifiable, to be portable to the vast majority of |
|
897 machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy |
|
898 to use. The ultimate goal of libpng is to promote the acceptance of |
|
899 the PNG file format in whatever way possible. While there is still |
|
900 work to be done (see the TODO file), libpng should cover the |
|
901 majority of the needs of its users. |
|
902 |
|
903 Libpng uses zlib for its compression and decompression of PNG files. |
|
904 Further information about zlib, and the latest version of zlib, can |
|
905 be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>. |
|
906 The zlib compression utility is a general purpose utility that is |
|
907 useful for more than PNG files, and can be used without libpng. |
|
908 See the documentation delivered with zlib for more details. |
|
909 You can usually find the source files for the zlib utility wherever you |
|
910 find the libpng source files. |
|
911 |
|
912 Libpng is thread safe, provided the threads are using different |
|
913 instances of the structures. Each thread should have its own |
|
914 png_struct and png_info instances, and thus its own image. |
|
915 Libpng does not protect itself against two threads using the |
|
916 same instance of a structure. |
|
917 |
|
918 .SH II. Structures |
|
919 |
|
920 There are two main structures that are important to libpng, png_struct |
|
921 and png_info. The first, png_struct, is an internal structure that |
|
922 will not, for the most part, be used by a user except as the first |
|
923 variable passed to every libpng function call. |
|
924 |
|
925 The png_info structure is designed to provide information about the |
|
926 PNG file. At one time, the fields of png_info were intended to be |
|
927 directly accessible to the user. However, this tended to cause problems |
|
928 with applications using dynamically loaded libraries, and as a result |
|
929 a set of interface functions for png_info (the png_get_*() and png_set_*() |
|
930 functions) was developed. The fields of png_info are still available for |
|
931 older applications, but it is suggested that applications use the new |
|
932 interfaces if at all possible. |
|
933 |
|
934 Applications that do make direct access to the members of png_struct (except |
|
935 for png_ptr->jmpbuf) must be recompiled whenever the library is updated, |
|
936 and applications that make direct access to the members of png_info must |
|
937 be recompiled if they were compiled or loaded with libpng version 1.0.6, |
|
938 in which the members were in a different order. In version 1.0.7, the |
|
939 members of the png_info structure reverted to the old order, as they were |
|
940 in versions 0.97c through 1.0.5. Starting with version 2.0.0, both |
|
941 structures are going to be hidden, and the contents of the structures will |
|
942 only be accessible through the png_get/png_set functions. |
|
943 |
|
944 The png.h header file is an invaluable reference for programming with libpng. |
|
945 And while I'm on the topic, make sure you include the libpng header file: |
|
946 |
|
947 #include <png.h> |
|
948 |
|
949 .SH III. Reading |
|
950 |
|
951 We'll now walk you through the possible functions to call when reading |
|
952 in a PNG file sequentially, briefly explaining the syntax and purpose |
|
953 of each one. See example.c and png.h for more detail. While |
|
954 progressive reading is covered in the next section, you will still |
|
955 need some of the functions discussed in this section to read a PNG |
|
956 file. |
|
957 |
|
958 .SS Setup |
|
959 |
|
960 You will want to do the I/O initialization(*) before you get into libpng, |
|
961 so if it doesn't work, you don't have much to undo. Of course, you |
|
962 will also want to insure that you are, in fact, dealing with a PNG |
|
963 file. Libpng provides a simple check to see if a file is a PNG file. |
|
964 To use it, pass in the first 1 to 8 bytes of the file to the function |
|
965 png_sig_cmp(), and it will return 0 if the bytes match the corresponding |
|
966 bytes of the PNG signature, or nonzero otherwise. Of course, the more bytes |
|
967 you pass in, the greater the accuracy of the prediction. |
|
968 |
|
969 If you are intending to keep the file pointer open for use in libpng, |
|
970 you must ensure you don't read more than 8 bytes from the beginning |
|
971 of the file, and you also have to make a call to png_set_sig_bytes_read() |
|
972 with the number of bytes you read from the beginning. Libpng will |
|
973 then only check the bytes (if any) that your program didn't read. |
|
974 |
|
975 (*): If you are not using the standard I/O functions, you will need |
|
976 to replace them with custom functions. See the discussion under |
|
977 Customizing libpng. |
|
978 |
|
979 |
|
980 FILE *fp = fopen(file_name, "rb"); |
|
981 if (!fp) |
|
982 { |
|
983 return (ERROR); |
|
984 } |
|
985 fread(header, 1, number, fp); |
|
986 is_png = !png_sig_cmp(header, 0, number); |
|
987 if (!is_png) |
|
988 { |
|
989 return (NOT_PNG); |
|
990 } |
|
991 |
|
992 |
|
993 Next, png_struct and png_info need to be allocated and initialized. In |
|
994 order to ensure that the size of these structures is correct even with a |
|
995 dynamically linked libpng, there are functions to initialize and |
|
996 allocate the structures. We also pass the library version, optional |
|
997 pointers to error handling functions, and a pointer to a data struct for |
|
998 use by the error functions, if necessary (the pointer and functions can |
|
999 be NULL if the default error handlers are to be used). See the section |
|
1000 on Changes to Libpng below regarding the old initialization functions. |
|
1001 The structure allocation functions quietly return NULL if they fail to |
|
1002 create the structure, so your application should check for that. |
|
1003 |
|
1004 png_structp png_ptr = png_create_read_struct |
|
1005 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
|
1006 user_error_fn, user_warning_fn); |
|
1007 if (!png_ptr) |
|
1008 return (ERROR); |
|
1009 |
|
1010 png_infop info_ptr = png_create_info_struct(png_ptr); |
|
1011 if (!info_ptr) |
|
1012 { |
|
1013 png_destroy_read_struct(&png_ptr, |
|
1014 (png_infopp)NULL, (png_infopp)NULL); |
|
1015 return (ERROR); |
|
1016 } |
|
1017 |
|
1018 png_infop end_info = png_create_info_struct(png_ptr); |
|
1019 if (!end_info) |
|
1020 { |
|
1021 png_destroy_read_struct(&png_ptr, &info_ptr, |
|
1022 (png_infopp)NULL); |
|
1023 return (ERROR); |
|
1024 } |
|
1025 |
|
1026 If you want to use your own memory allocation routines, |
|
1027 define PNG_USER_MEM_SUPPORTED and use |
|
1028 png_create_read_struct_2() instead of png_create_read_struct(): |
|
1029 |
|
1030 png_structp png_ptr = png_create_read_struct_2 |
|
1031 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
|
1032 user_error_fn, user_warning_fn, (png_voidp) |
|
1033 user_mem_ptr, user_malloc_fn, user_free_fn); |
|
1034 |
|
1035 The error handling routines passed to png_create_read_struct() |
|
1036 and the memory alloc/free routines passed to png_create_struct_2() |
|
1037 are only necessary if you are not using the libpng supplied error |
|
1038 handling and memory alloc/free functions. |
|
1039 |
|
1040 When libpng encounters an error, it expects to longjmp back |
|
1041 to your routine. Therefore, you will need to call setjmp and pass |
|
1042 your png_jmpbuf(png_ptr). If you read the file from different |
|
1043 routines, you will need to update the jmpbuf field every time you enter |
|
1044 a new routine that will call a png_*() function. |
|
1045 |
|
1046 See your documentation of setjmp/longjmp for your compiler for more |
|
1047 information on setjmp/longjmp. See the discussion on libpng error |
|
1048 handling in the Customizing Libpng section below for more information |
|
1049 on the libpng error handling. If an error occurs, and libpng longjmp's |
|
1050 back to your setjmp, you will want to call png_destroy_read_struct() to |
|
1051 free any memory. |
|
1052 |
|
1053 if (setjmp(png_jmpbuf(png_ptr))) |
|
1054 { |
|
1055 png_destroy_read_struct(&png_ptr, &info_ptr, |
|
1056 &end_info); |
|
1057 fclose(fp); |
|
1058 return (ERROR); |
|
1059 } |
|
1060 |
|
1061 If you would rather avoid the complexity of setjmp/longjmp issues, |
|
1062 you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case |
|
1063 errors will result in a call to PNG_ABORT() which defaults to abort(). |
|
1064 |
|
1065 Now you need to set up the input code. The default for libpng is to |
|
1066 use the C function fread(). If you use this, you will need to pass a |
|
1067 valid FILE * in the function png_init_io(). Be sure that the file is |
|
1068 opened in binary mode. If you wish to handle reading data in another |
|
1069 way, you need not call the png_init_io() function, but you must then |
|
1070 implement the libpng I/O methods discussed in the Customizing Libpng |
|
1071 section below. |
|
1072 |
|
1073 png_init_io(png_ptr, fp); |
|
1074 |
|
1075 If you had previously opened the file and read any of the signature from |
|
1076 the beginning in order to see if this was a PNG file, you need to let |
|
1077 libpng know that there are some bytes missing from the start of the file. |
|
1078 |
|
1079 png_set_sig_bytes(png_ptr, number); |
|
1080 |
|
1081 .SS Setting up callback code |
|
1082 |
|
1083 You can set up a callback function to handle any unknown chunks in the |
|
1084 input stream. You must supply the function |
|
1085 |
|
1086 read_chunk_callback(png_ptr ptr, |
|
1087 png_unknown_chunkp chunk); |
|
1088 { |
|
1089 /* The unknown chunk structure contains your |
|
1090 chunk data, along with similar data for any other |
|
1091 unknown chunks: */ |
|
1092 |
|
1093 png_byte name[5]; |
|
1094 png_byte *data; |
|
1095 png_size_t size; |
|
1096 |
|
1097 /* Note that libpng has already taken care of |
|
1098 the CRC handling */ |
|
1099 |
|
1100 /* put your code here. Search for your chunk in the |
|
1101 unknown chunk structure, process it, and return one |
|
1102 of the following: */ |
|
1103 |
|
1104 return (-n); /* chunk had an error */ |
|
1105 return (0); /* did not recognize */ |
|
1106 return (n); /* success */ |
|
1107 } |
|
1108 |
|
1109 (You can give your function another name that you like instead of |
|
1110 "read_chunk_callback") |
|
1111 |
|
1112 To inform libpng about your function, use |
|
1113 |
|
1114 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr, |
|
1115 read_chunk_callback); |
|
1116 |
|
1117 This names not only the callback function, but also a user pointer that |
|
1118 you can retrieve with |
|
1119 |
|
1120 png_get_user_chunk_ptr(png_ptr); |
|
1121 |
|
1122 If you call the png_set_read_user_chunk_fn() function, then all unknown |
|
1123 chunks will be saved when read, in case your callback function will need |
|
1124 one or more of them. This behavior can be changed with the |
|
1125 png_set_keep_unknown_chunks() function, described below. |
|
1126 |
|
1127 At this point, you can set up a callback function that will be |
|
1128 called after each row has been read, which you can use to control |
|
1129 a progress meter or the like. It's demonstrated in pngtest.c. |
|
1130 You must supply a function |
|
1131 |
|
1132 void read_row_callback(png_ptr ptr, png_uint_32 row, |
|
1133 int pass); |
|
1134 { |
|
1135 /* put your code here */ |
|
1136 } |
|
1137 |
|
1138 (You can give it another name that you like instead of "read_row_callback") |
|
1139 |
|
1140 To inform libpng about your function, use |
|
1141 |
|
1142 png_set_read_status_fn(png_ptr, read_row_callback); |
|
1143 |
|
1144 .SS Width and height limits |
|
1145 |
|
1146 The PNG specification allows the width and height of an image to be as |
|
1147 large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns. |
|
1148 Since very few applications really need to process such large images, |
|
1149 we have imposed an arbitrary 1-million limit on rows and columns. |
|
1150 Larger images will be rejected immediately with a png_error() call. If |
|
1151 you wish to override this limit, you can use |
|
1152 |
|
1153 png_set_user_limits(png_ptr, width_max, height_max); |
|
1154 |
|
1155 to set your own limits, or use width_max = height_max = 0x7fffffffL |
|
1156 to allow all valid dimensions (libpng may reject some very large images |
|
1157 anyway because of potential buffer overflow conditions). |
|
1158 |
|
1159 You should put this statement after you create the PNG structure and |
|
1160 before calling png_read_info(), png_read_png(), or png_process_data(). |
|
1161 If you need to retrieve the limits that are being applied, use |
|
1162 |
|
1163 width_max = png_get_user_width_max(png_ptr); |
|
1164 height_max = png_get_user_height_max(png_ptr); |
|
1165 |
|
1166 .SS Unknown-chunk handling |
|
1167 |
|
1168 Now you get to set the way the library processes unknown chunks in the |
|
1169 input PNG stream. Both known and unknown chunks will be read. Normal |
|
1170 behavior is that known chunks will be parsed into information in |
|
1171 various info_ptr members while unknown chunks will be discarded. To change |
|
1172 this, you can call: |
|
1173 |
|
1174 png_set_keep_unknown_chunks(png_ptr, keep, |
|
1175 chunk_list, num_chunks); |
|
1176 keep - 0: default unknown chunk handling |
|
1177 1: ignore; do not keep |
|
1178 2: keep only if safe-to-copy |
|
1179 3: keep even if unsafe-to-copy |
|
1180 You can use these definitions: |
|
1181 PNG_HANDLE_CHUNK_AS_DEFAULT 0 |
|
1182 PNG_HANDLE_CHUNK_NEVER 1 |
|
1183 PNG_HANDLE_CHUNK_IF_SAFE 2 |
|
1184 PNG_HANDLE_CHUNK_ALWAYS 3 |
|
1185 chunk_list - list of chunks affected (a byte string, |
|
1186 five bytes per chunk, NULL or '\0' if |
|
1187 num_chunks is 0) |
|
1188 num_chunks - number of chunks affected; if 0, all |
|
1189 unknown chunks are affected. If nonzero, |
|
1190 only the chunks in the list are affected |
|
1191 |
|
1192 Unknown chunks declared in this way will be saved as raw data onto a |
|
1193 list of png_unknown_chunk structures. If a chunk that is normally |
|
1194 known to libpng is named in the list, it will be handled as unknown, |
|
1195 according to the "keep" directive. If a chunk is named in successive |
|
1196 instances of png_set_keep_unknown_chunks(), the final instance will |
|
1197 take precedence. The IHDR and IEND chunks should not be named in |
|
1198 chunk_list; if they are, libpng will process them normally anyway. |
|
1199 |
|
1200 Here is an example of the usage of png_set_keep_unknown_chunks(), |
|
1201 where the private "vpAg" chunk will later be processed by a user chunk |
|
1202 callback function: |
|
1203 |
|
1204 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'}; |
|
1205 |
|
1206 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) |
|
1207 png_byte unused_chunks[]= |
|
1208 { |
|
1209 104, 73, 83, 84, (png_byte) '\0', /* hIST */ |
|
1210 105, 84, 88, 116, (png_byte) '\0', /* iTXt */ |
|
1211 112, 67, 65, 76, (png_byte) '\0', /* pCAL */ |
|
1212 115, 67, 65, 76, (png_byte) '\0', /* sCAL */ |
|
1213 115, 80, 76, 84, (png_byte) '\0', /* sPLT */ |
|
1214 116, 73, 77, 69, (png_byte) '\0', /* tIME */ |
|
1215 }; |
|
1216 #endif |
|
1217 |
|
1218 ... |
|
1219 |
|
1220 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) |
|
1221 /* ignore all unknown chunks: */ |
|
1222 png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); |
|
1223 /* except for vpAg: */ |
|
1224 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); |
|
1225 /* also ignore unused known chunks: */ |
|
1226 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, |
|
1227 (int)sizeof(unused_chunks)/5); |
|
1228 #endif |
|
1229 |
|
1230 |
|
1231 .SS The high-level read interface |
|
1232 |
|
1233 At this point there are two ways to proceed; through the high-level |
|
1234 read interface, or through a sequence of low-level read operations. |
|
1235 You can use the high-level interface if (a) you are willing to read |
|
1236 the entire image into memory, and (b) the input transformations |
|
1237 you want to do are limited to the following set: |
|
1238 |
|
1239 PNG_TRANSFORM_IDENTITY No transformation |
|
1240 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to |
|
1241 8 bits |
|
1242 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel |
|
1243 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit |
|
1244 samples to bytes |
|
1245 PNG_TRANSFORM_PACKSWAP Change order of packed |
|
1246 pixels to LSB first |
|
1247 PNG_TRANSFORM_EXPAND Perform set_expand() |
|
1248 PNG_TRANSFORM_INVERT_MONO Invert monochrome images |
|
1249 PNG_TRANSFORM_SHIFT Normalize pixels to the |
|
1250 sBIT depth |
|
1251 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA |
|
1252 to BGRA |
|
1253 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA |
|
1254 to AG |
|
1255 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity |
|
1256 to transparency |
|
1257 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples |
|
1258 |
|
1259 (This excludes setting a background color, doing gamma transformation, |
|
1260 dithering, and setting filler.) If this is the case, simply do this: |
|
1261 |
|
1262 png_read_png(png_ptr, info_ptr, png_transforms, NULL) |
|
1263 |
|
1264 where png_transforms is an integer containing the bitwise OR of |
|
1265 some set of transformation flags. This call is equivalent to png_read_info(), |
|
1266 followed the set of transformations indicated by the transform mask, |
|
1267 then png_read_image(), and finally png_read_end(). |
|
1268 |
|
1269 (The final parameter of this call is not yet used. Someday it might point |
|
1270 to transformation parameters required by some future input transform.) |
|
1271 |
|
1272 You must use png_transforms and not call any png_set_transform() functions |
|
1273 when you use png_read_png(). |
|
1274 |
|
1275 After you have called png_read_png(), you can retrieve the image data |
|
1276 with |
|
1277 |
|
1278 row_pointers = png_get_rows(png_ptr, info_ptr); |
|
1279 |
|
1280 where row_pointers is an array of pointers to the pixel data for each row: |
|
1281 |
|
1282 png_bytep row_pointers[height]; |
|
1283 |
|
1284 If you know your image size and pixel size ahead of time, you can allocate |
|
1285 row_pointers prior to calling png_read_png() with |
|
1286 |
|
1287 if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) |
|
1288 png_error (png_ptr, |
|
1289 "Image is too tall to process in memory"); |
|
1290 if (width > PNG_UINT_32_MAX/pixel_size) |
|
1291 png_error (png_ptr, |
|
1292 "Image is too wide to process in memory"); |
|
1293 row_pointers = png_malloc(png_ptr, |
|
1294 height*png_sizeof(png_bytep)); |
|
1295 for (int i=0; i<height, i++) |
|
1296 row_pointers[i]=png_malloc(png_ptr, |
|
1297 width*pixel_size); |
|
1298 png_set_rows(png_ptr, info_ptr, &row_pointers); |
|
1299 |
|
1300 Alternatively you could allocate your image in one big block and define |
|
1301 row_pointers[i] to point into the proper places in your block. |
|
1302 |
|
1303 If you use png_set_rows(), the application is responsible for freeing |
|
1304 row_pointers (and row_pointers[i], if they were separately allocated). |
|
1305 |
|
1306 If you don't allocate row_pointers ahead of time, png_read_png() will |
|
1307 do it, and it'll be free'ed when you call png_destroy_*(). |
|
1308 |
|
1309 .SS The low-level read interface |
|
1310 |
|
1311 If you are going the low-level route, you are now ready to read all |
|
1312 the file information up to the actual image data. You do this with a |
|
1313 call to png_read_info(). |
|
1314 |
|
1315 png_read_info(png_ptr, info_ptr); |
|
1316 |
|
1317 This will process all chunks up to but not including the image data. |
|
1318 |
|
1319 .SS Querying the info structure |
|
1320 |
|
1321 Functions are used to get the information from the info_ptr once it |
|
1322 has been read. Note that these fields may not be completely filled |
|
1323 in until png_read_end() has read the chunk data following the image. |
|
1324 |
|
1325 png_get_IHDR(png_ptr, info_ptr, &width, &height, |
|
1326 &bit_depth, &color_type, &interlace_type, |
|
1327 &compression_type, &filter_method); |
|
1328 |
|
1329 width - holds the width of the image |
|
1330 in pixels (up to 2^31). |
|
1331 height - holds the height of the image |
|
1332 in pixels (up to 2^31). |
|
1333 bit_depth - holds the bit depth of one of the |
|
1334 image channels. (valid values are |
|
1335 1, 2, 4, 8, 16 and depend also on |
|
1336 the color_type. See also |
|
1337 significant bits (sBIT) below). |
|
1338 color_type - describes which color/alpha channels |
|
1339 are present. |
|
1340 PNG_COLOR_TYPE_GRAY |
|
1341 (bit depths 1, 2, 4, 8, 16) |
|
1342 PNG_COLOR_TYPE_GRAY_ALPHA |
|
1343 (bit depths 8, 16) |
|
1344 PNG_COLOR_TYPE_PALETTE |
|
1345 (bit depths 1, 2, 4, 8) |
|
1346 PNG_COLOR_TYPE_RGB |
|
1347 (bit_depths 8, 16) |
|
1348 PNG_COLOR_TYPE_RGB_ALPHA |
|
1349 (bit_depths 8, 16) |
|
1350 |
|
1351 PNG_COLOR_MASK_PALETTE |
|
1352 PNG_COLOR_MASK_COLOR |
|
1353 PNG_COLOR_MASK_ALPHA |
|
1354 |
|
1355 filter_method - (must be PNG_FILTER_TYPE_BASE |
|
1356 for PNG 1.0, and can also be |
|
1357 PNG_INTRAPIXEL_DIFFERENCING if |
|
1358 the PNG datastream is embedded in |
|
1359 a MNG-1.0 datastream) |
|
1360 compression_type - (must be PNG_COMPRESSION_TYPE_BASE |
|
1361 for PNG 1.0) |
|
1362 interlace_type - (PNG_INTERLACE_NONE or |
|
1363 PNG_INTERLACE_ADAM7) |
|
1364 Any or all of interlace_type, compression_type, of |
|
1365 filter_method can be NULL if you are |
|
1366 not interested in their values. |
|
1367 |
|
1368 channels = png_get_channels(png_ptr, info_ptr); |
|
1369 channels - number of channels of info for the |
|
1370 color type (valid values are 1 (GRAY, |
|
1371 PALETTE), 2 (GRAY_ALPHA), 3 (RGB), |
|
1372 4 (RGB_ALPHA or RGB + filler byte)) |
|
1373 rowbytes = png_get_rowbytes(png_ptr, info_ptr); |
|
1374 rowbytes - number of bytes needed to hold a row |
|
1375 |
|
1376 signature = png_get_signature(png_ptr, info_ptr); |
|
1377 signature - holds the signature read from the |
|
1378 file (if any). The data is kept in |
|
1379 the same offset it would be if the |
|
1380 whole signature were read (i.e. if an |
|
1381 application had already read in 4 |
|
1382 bytes of signature before starting |
|
1383 libpng, the remaining 4 bytes would |
|
1384 be in signature[4] through signature[7] |
|
1385 (see png_set_sig_bytes())). |
|
1386 |
|
1387 |
|
1388 width = png_get_image_width(png_ptr, |
|
1389 info_ptr); |
|
1390 height = png_get_image_height(png_ptr, |
|
1391 info_ptr); |
|
1392 bit_depth = png_get_bit_depth(png_ptr, |
|
1393 info_ptr); |
|
1394 color_type = png_get_color_type(png_ptr, |
|
1395 info_ptr); |
|
1396 filter_method = png_get_filter_type(png_ptr, |
|
1397 info_ptr); |
|
1398 compression_type = png_get_compression_type(png_ptr, |
|
1399 info_ptr); |
|
1400 interlace_type = png_get_interlace_type(png_ptr, |
|
1401 info_ptr); |
|
1402 |
|
1403 |
|
1404 These are also important, but their validity depends on whether the chunk |
|
1405 has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and |
|
1406 png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the |
|
1407 data has been read, or zero if it is missing. The parameters to the |
|
1408 png_get_<chunk> are set directly if they are simple data types, or a pointer |
|
1409 into the info_ptr is returned for any complex types. |
|
1410 |
|
1411 png_get_PLTE(png_ptr, info_ptr, &palette, |
|
1412 &num_palette); |
|
1413 palette - the palette for the file |
|
1414 (array of png_color) |
|
1415 num_palette - number of entries in the palette |
|
1416 |
|
1417 png_get_gAMA(png_ptr, info_ptr, &gamma); |
|
1418 gamma - the gamma the file is written |
|
1419 at (PNG_INFO_gAMA) |
|
1420 |
|
1421 png_get_sRGB(png_ptr, info_ptr, &srgb_intent); |
|
1422 srgb_intent - the rendering intent (PNG_INFO_sRGB) |
|
1423 The presence of the sRGB chunk |
|
1424 means that the pixel data is in the |
|
1425 sRGB color space. This chunk also |
|
1426 implies specific values of gAMA and |
|
1427 cHRM. |
|
1428 |
|
1429 png_get_iCCP(png_ptr, info_ptr, &name, |
|
1430 &compression_type, &profile, &proflen); |
|
1431 name - The profile name. |
|
1432 compression - The compression type; always |
|
1433 PNG_COMPRESSION_TYPE_BASE for PNG 1.0. |
|
1434 You may give NULL to this argument to |
|
1435 ignore it. |
|
1436 profile - International Color Consortium color |
|
1437 profile data. May contain NULs. |
|
1438 proflen - length of profile data in bytes. |
|
1439 |
|
1440 png_get_sBIT(png_ptr, info_ptr, &sig_bit); |
|
1441 sig_bit - the number of significant bits for |
|
1442 (PNG_INFO_sBIT) each of the gray, |
|
1443 red, green, and blue channels, |
|
1444 whichever are appropriate for the |
|
1445 given color type (png_color_16) |
|
1446 |
|
1447 png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, |
|
1448 &trans_values); |
|
1449 trans - array of transparent entries for |
|
1450 palette (PNG_INFO_tRNS) |
|
1451 trans_values - graylevel or color sample values of |
|
1452 the single transparent color for |
|
1453 non-paletted images (PNG_INFO_tRNS) |
|
1454 num_trans - number of transparent entries |
|
1455 (PNG_INFO_tRNS) |
|
1456 |
|
1457 png_get_hIST(png_ptr, info_ptr, &hist); |
|
1458 (PNG_INFO_hIST) |
|
1459 hist - histogram of palette (array of |
|
1460 png_uint_16) |
|
1461 |
|
1462 png_get_tIME(png_ptr, info_ptr, &mod_time); |
|
1463 mod_time - time image was last modified |
|
1464 (PNG_VALID_tIME) |
|
1465 |
|
1466 png_get_bKGD(png_ptr, info_ptr, &background); |
|
1467 background - background color (PNG_VALID_bKGD) |
|
1468 valid 16-bit red, green and blue |
|
1469 values, regardless of color_type |
|
1470 |
|
1471 num_comments = png_get_text(png_ptr, info_ptr, |
|
1472 &text_ptr, &num_text); |
|
1473 num_comments - number of comments |
|
1474 text_ptr - array of png_text holding image |
|
1475 comments |
|
1476 text_ptr[i].compression - type of compression used |
|
1477 on "text" PNG_TEXT_COMPRESSION_NONE |
|
1478 PNG_TEXT_COMPRESSION_zTXt |
|
1479 PNG_ITXT_COMPRESSION_NONE |
|
1480 PNG_ITXT_COMPRESSION_zTXt |
|
1481 text_ptr[i].key - keyword for comment. Must contain |
|
1482 1-79 characters. |
|
1483 text_ptr[i].text - text comments for current |
|
1484 keyword. Can be empty. |
|
1485 text_ptr[i].text_length - length of text string, |
|
1486 after decompression, 0 for iTXt |
|
1487 text_ptr[i].itxt_length - length of itxt string, |
|
1488 after decompression, 0 for tEXt/zTXt |
|
1489 text_ptr[i].lang - language of comment (empty |
|
1490 string for unknown). |
|
1491 text_ptr[i].lang_key - keyword in UTF-8 |
|
1492 (empty string for unknown). |
|
1493 num_text - number of comments (same as |
|
1494 num_comments; you can put NULL here |
|
1495 to avoid the duplication) |
|
1496 Note while png_set_text() will accept text, language, |
|
1497 and translated keywords that can be NULL pointers, the |
|
1498 structure returned by png_get_text will always contain |
|
1499 regular zero-terminated C strings. They might be |
|
1500 empty strings but they will never be NULL pointers. |
|
1501 |
|
1502 num_spalettes = png_get_sPLT(png_ptr, info_ptr, |
|
1503 &palette_ptr); |
|
1504 palette_ptr - array of palette structures holding |
|
1505 contents of one or more sPLT chunks |
|
1506 read. |
|
1507 num_spalettes - number of sPLT chunks read. |
|
1508 |
|
1509 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, |
|
1510 &unit_type); |
|
1511 offset_x - positive offset from the left edge |
|
1512 of the screen |
|
1513 offset_y - positive offset from the top edge |
|
1514 of the screen |
|
1515 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER |
|
1516 |
|
1517 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, |
|
1518 &unit_type); |
|
1519 res_x - pixels/unit physical resolution in |
|
1520 x direction |
|
1521 res_y - pixels/unit physical resolution in |
|
1522 x direction |
|
1523 unit_type - PNG_RESOLUTION_UNKNOWN, |
|
1524 PNG_RESOLUTION_METER |
|
1525 |
|
1526 png_get_sCAL(png_ptr, info_ptr, &unit, &width, |
|
1527 &height) |
|
1528 unit - physical scale units (an integer) |
|
1529 width - width of a pixel in physical scale units |
|
1530 height - height of a pixel in physical scale units |
|
1531 (width and height are doubles) |
|
1532 |
|
1533 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, |
|
1534 &height) |
|
1535 unit - physical scale units (an integer) |
|
1536 width - width of a pixel in physical scale units |
|
1537 height - height of a pixel in physical scale units |
|
1538 (width and height are strings like "2.54") |
|
1539 |
|
1540 num_unknown_chunks = png_get_unknown_chunks(png_ptr, |
|
1541 info_ptr, &unknowns) |
|
1542 unknowns - array of png_unknown_chunk |
|
1543 structures holding unknown chunks |
|
1544 unknowns[i].name - name of unknown chunk |
|
1545 unknowns[i].data - data of unknown chunk |
|
1546 unknowns[i].size - size of unknown chunk's data |
|
1547 unknowns[i].location - position of chunk in file |
|
1548 |
|
1549 The value of "i" corresponds to the order in which the |
|
1550 chunks were read from the PNG file or inserted with the |
|
1551 png_set_unknown_chunks() function. |
|
1552 |
|
1553 The data from the pHYs chunk can be retrieved in several convenient |
|
1554 forms: |
|
1555 |
|
1556 res_x = png_get_x_pixels_per_meter(png_ptr, |
|
1557 info_ptr) |
|
1558 res_y = png_get_y_pixels_per_meter(png_ptr, |
|
1559 info_ptr) |
|
1560 res_x_and_y = png_get_pixels_per_meter(png_ptr, |
|
1561 info_ptr) |
|
1562 res_x = png_get_x_pixels_per_inch(png_ptr, |
|
1563 info_ptr) |
|
1564 res_y = png_get_y_pixels_per_inch(png_ptr, |
|
1565 info_ptr) |
|
1566 res_x_and_y = png_get_pixels_per_inch(png_ptr, |
|
1567 info_ptr) |
|
1568 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, |
|
1569 info_ptr) |
|
1570 |
|
1571 (Each of these returns 0 [signifying "unknown"] if |
|
1572 the data is not present or if res_x is 0; |
|
1573 res_x_and_y is 0 if res_x != res_y) |
|
1574 |
|
1575 The data from the oFFs chunk can be retrieved in several convenient |
|
1576 forms: |
|
1577 |
|
1578 x_offset = png_get_x_offset_microns(png_ptr, info_ptr); |
|
1579 y_offset = png_get_y_offset_microns(png_ptr, info_ptr); |
|
1580 x_offset = png_get_x_offset_inches(png_ptr, info_ptr); |
|
1581 y_offset = png_get_y_offset_inches(png_ptr, info_ptr); |
|
1582 |
|
1583 (Each of these returns 0 [signifying "unknown" if both |
|
1584 x and y are 0] if the data is not present or if the |
|
1585 chunk is present but the unit is the pixel) |
|
1586 |
|
1587 For more information, see the png_info definition in png.h and the |
|
1588 PNG specification for chunk contents. Be careful with trusting |
|
1589 rowbytes, as some of the transformations could increase the space |
|
1590 needed to hold a row (expand, filler, gray_to_rgb, etc.). |
|
1591 See png_read_update_info(), below. |
|
1592 |
|
1593 A quick word about text_ptr and num_text. PNG stores comments in |
|
1594 keyword/text pairs, one pair per chunk, with no limit on the number |
|
1595 of text chunks, and a 2^31 byte limit on their size. While there are |
|
1596 suggested keywords, there is no requirement to restrict the use to these |
|
1597 strings. It is strongly suggested that keywords and text be sensible |
|
1598 to humans (that's the point), so don't use abbreviations. Non-printing |
|
1599 symbols are not allowed. See the PNG specification for more details. |
|
1600 There is also no requirement to have text after the keyword. |
|
1601 |
|
1602 Keywords should be limited to 79 Latin-1 characters without leading or |
|
1603 trailing spaces, but non-consecutive spaces are allowed within the |
|
1604 keyword. It is possible to have the same keyword any number of times. |
|
1605 The text_ptr is an array of png_text structures, each holding a |
|
1606 pointer to a language string, a pointer to a keyword and a pointer to |
|
1607 a text string. The text string, language code, and translated |
|
1608 keyword may be empty or NULL pointers. The keyword/text |
|
1609 pairs are put into the array in the order that they are received. |
|
1610 However, some or all of the text chunks may be after the image, so, to |
|
1611 make sure you have read all the text chunks, don't mess with these |
|
1612 until after you read the stuff after the image. This will be |
|
1613 mentioned again below in the discussion that goes with png_read_end(). |
|
1614 |
|
1615 .SS Input transformations |
|
1616 |
|
1617 After you've read the header information, you can set up the library |
|
1618 to handle any special transformations of the image data. The various |
|
1619 ways to transform the data will be described in the order that they |
|
1620 should occur. This is important, as some of these change the color |
|
1621 type and/or bit depth of the data, and some others only work on |
|
1622 certain color types and bit depths. Even though each transformation |
|
1623 checks to see if it has data that it can do something with, you should |
|
1624 make sure to only enable a transformation if it will be valid for the |
|
1625 data. For example, don't swap red and blue on grayscale data. |
|
1626 |
|
1627 The colors used for the background and transparency values should be |
|
1628 supplied in the same format/depth as the current image data. They |
|
1629 are stored in the same format/depth as the image data in a bKGD or tRNS |
|
1630 chunk, so this is what libpng expects for this data. The colors are |
|
1631 transformed to keep in sync with the image data when an application |
|
1632 calls the png_read_update_info() routine (see below). |
|
1633 |
|
1634 Data will be decoded into the supplied row buffers packed into bytes |
|
1635 unless the library has been told to transform it into another format. |
|
1636 For example, 4 bit/pixel paletted or grayscale data will be returned |
|
1637 2 pixels/byte with the leftmost pixel in the high-order bits of the |
|
1638 byte, unless png_set_packing() is called. 8-bit RGB data will be stored |
|
1639 in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() |
|
1640 is called to insert filler bytes, either before or after each RGB triplet. |
|
1641 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant |
|
1642 byte of the color value first, unless png_set_strip_16() is called to |
|
1643 transform it to regular RGB RGB triplets, or png_set_filler() or |
|
1644 png_set_add alpha() is called to insert filler bytes, either before or |
|
1645 after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can |
|
1646 be modified with |
|
1647 png_set_filler(), png_set_add_alpha(), or png_set_strip_16(). |
|
1648 |
|
1649 The following code transforms grayscale images of less than 8 to 8 bits, |
|
1650 changes paletted images to RGB, and adds a full alpha channel if there is |
|
1651 transparency information in a tRNS chunk. This is most useful on |
|
1652 grayscale images with bit depths of 2 or 4 or if there is a multiple-image |
|
1653 viewing application that wishes to treat all images in the same way. |
|
1654 |
|
1655 if (color_type == PNG_COLOR_TYPE_PALETTE) |
|
1656 png_set_palette_to_rgb(png_ptr); |
|
1657 |
|
1658 if (color_type == PNG_COLOR_TYPE_GRAY && |
|
1659 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); |
|
1660 |
|
1661 if (png_get_valid(png_ptr, info_ptr, |
|
1662 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); |
|
1663 |
|
1664 These three functions are actually aliases for png_set_expand(), added |
|
1665 in libpng version 1.0.4, with the function names expanded to improve code |
|
1666 readability. In some future version they may actually do different |
|
1667 things. |
|
1668 |
|
1669 As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was |
|
1670 added. It expands the sample depth without changing tRNS to alpha. |
|
1671 At the same time, png_set_gray_1_2_4_to_8() was deprecated, and it |
|
1672 will be removed from a future version. |
|
1673 |
|
1674 |
|
1675 PNG can have files with 16 bits per channel. If you only can handle |
|
1676 8 bits per channel, this will strip the pixels down to 8 bit. |
|
1677 |
|
1678 if (bit_depth == 16) |
|
1679 png_set_strip_16(png_ptr); |
|
1680 |
|
1681 If, for some reason, you don't need the alpha channel on an image, |
|
1682 and you want to remove it rather than combining it with the background |
|
1683 (but the image author certainly had in mind that you *would* combine |
|
1684 it with the background, so that's what you should probably do): |
|
1685 |
|
1686 if (color_type & PNG_COLOR_MASK_ALPHA) |
|
1687 png_set_strip_alpha(png_ptr); |
|
1688 |
|
1689 In PNG files, the alpha channel in an image |
|
1690 is the level of opacity. If you need the alpha channel in an image to |
|
1691 be the level of transparency instead of opacity, you can invert the |
|
1692 alpha channel (or the tRNS chunk data) after it's read, so that 0 is |
|
1693 fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit |
|
1694 images) is fully transparent, with |
|
1695 |
|
1696 png_set_invert_alpha(png_ptr); |
|
1697 |
|
1698 PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as |
|
1699 they can, resulting in, for example, 8 pixels per byte for 1 bit |
|
1700 files. This code expands to 1 pixel per byte without changing the |
|
1701 values of the pixels: |
|
1702 |
|
1703 if (bit_depth < 8) |
|
1704 png_set_packing(png_ptr); |
|
1705 |
|
1706 PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels |
|
1707 stored in a PNG image have been "scaled" or "shifted" up to the next |
|
1708 higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] to |
|
1709 8 bits/sample in the range [0, 255]). However, it is also possible to |
|
1710 convert the PNG pixel data back to the original bit depth of the image. |
|
1711 This call reduces the pixels back down to the original bit depth: |
|
1712 |
|
1713 png_color_8p sig_bit; |
|
1714 |
|
1715 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) |
|
1716 png_set_shift(png_ptr, sig_bit); |
|
1717 |
|
1718 PNG files store 3-color pixels in red, green, blue order. This code |
|
1719 changes the storage of the pixels to blue, green, red: |
|
1720 |
|
1721 if (color_type == PNG_COLOR_TYPE_RGB || |
|
1722 color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
|
1723 png_set_bgr(png_ptr); |
|
1724 |
|
1725 PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them |
|
1726 into 4 or 8 bytes for windowing systems that need them in this format: |
|
1727 |
|
1728 if (color_type == PNG_COLOR_TYPE_RGB) |
|
1729 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); |
|
1730 |
|
1731 where "filler" is the 8 or 16-bit number to fill with, and the location is |
|
1732 either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether |
|
1733 you want the filler before the RGB or after. This transformation |
|
1734 does not affect images that already have full alpha channels. To add an |
|
1735 opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which |
|
1736 will generate RGBA pixels. |
|
1737 |
|
1738 Note that png_set_filler() does not change the color type. If you want |
|
1739 to do that, you can add a true alpha channel with |
|
1740 |
|
1741 if (color_type == PNG_COLOR_TYPE_RGB || |
|
1742 color_type == PNG_COLOR_TYPE_GRAY) |
|
1743 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); |
|
1744 |
|
1745 where "filler" contains the alpha value to assign to each pixel. |
|
1746 This function was added in libpng-1.2.7. |
|
1747 |
|
1748 If you are reading an image with an alpha channel, and you need the |
|
1749 data as ARGB instead of the normal PNG format RGBA: |
|
1750 |
|
1751 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
|
1752 png_set_swap_alpha(png_ptr); |
|
1753 |
|
1754 For some uses, you may want a grayscale image to be represented as |
|
1755 RGB. This code will do that conversion: |
|
1756 |
|
1757 if (color_type == PNG_COLOR_TYPE_GRAY || |
|
1758 color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
|
1759 png_set_gray_to_rgb(png_ptr); |
|
1760 |
|
1761 Conversely, you can convert an RGB or RGBA image to grayscale or grayscale |
|
1762 with alpha. |
|
1763 |
|
1764 if (color_type == PNG_COLOR_TYPE_RGB || |
|
1765 color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
|
1766 png_set_rgb_to_gray_fixed(png_ptr, error_action, |
|
1767 int red_weight, int green_weight); |
|
1768 |
|
1769 error_action = 1: silently do the conversion |
|
1770 error_action = 2: issue a warning if the original |
|
1771 image has any pixel where |
|
1772 red != green or red != blue |
|
1773 error_action = 3: issue an error and abort the |
|
1774 conversion if the original |
|
1775 image has any pixel where |
|
1776 red != green or red != blue |
|
1777 |
|
1778 red_weight: weight of red component times 100000 |
|
1779 green_weight: weight of green component times 100000 |
|
1780 If either weight is negative, default |
|
1781 weights (21268, 71514) are used. |
|
1782 |
|
1783 If you have set error_action = 1 or 2, you can |
|
1784 later check whether the image really was gray, after processing |
|
1785 the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. |
|
1786 It will return a png_byte that is zero if the image was gray or |
|
1787 1 if there were any non-gray pixels. bKGD and sBIT data |
|
1788 will be silently converted to grayscale, using the green channel |
|
1789 data, regardless of the error_action setting. |
|
1790 |
|
1791 With red_weight+green_weight<=100000, |
|
1792 the normalized graylevel is computed: |
|
1793 |
|
1794 int rw = red_weight * 65536; |
|
1795 int gw = green_weight * 65536; |
|
1796 int bw = 65536 - (rw + gw); |
|
1797 gray = (rw*red + gw*green + bw*blue)/65536; |
|
1798 |
|
1799 The default values approximate those recommended in the Charles |
|
1800 Poynton's Color FAQ, <http://www.inforamp.net/~poynton/> |
|
1801 Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net> |
|
1802 |
|
1803 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B |
|
1804 |
|
1805 Libpng approximates this with |
|
1806 |
|
1807 Y = 0.21268 * R + 0.7151 * G + 0.07217 * B |
|
1808 |
|
1809 which can be expressed with integers as |
|
1810 |
|
1811 Y = (6969 * R + 23434 * G + 2365 * B)/32768 |
|
1812 |
|
1813 The calculation is done in a linear colorspace, if the image gamma |
|
1814 is known. |
|
1815 |
|
1816 If you have a grayscale and you are using png_set_expand_depth(), |
|
1817 png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to |
|
1818 a higher bit-depth, you must either supply the background color as a gray |
|
1819 value at the original file bit-depth (need_expand = 1) or else supply the |
|
1820 background color as an RGB triplet at the final, expanded bit depth |
|
1821 (need_expand = 0). Similarly, if you are reading a paletted image, you |
|
1822 must either supply the background color as a palette index (need_expand = 1) |
|
1823 or as an RGB triplet that may or may not be in the palette (need_expand = 0). |
|
1824 |
|
1825 png_color_16 my_background; |
|
1826 png_color_16p image_background; |
|
1827 |
|
1828 if (png_get_bKGD(png_ptr, info_ptr, &image_background)) |
|
1829 png_set_background(png_ptr, image_background, |
|
1830 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); |
|
1831 else |
|
1832 png_set_background(png_ptr, &my_background, |
|
1833 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); |
|
1834 |
|
1835 The png_set_background() function tells libpng to composite images |
|
1836 with alpha or simple transparency against the supplied background |
|
1837 color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), |
|
1838 you may use this color, or supply another color more suitable for |
|
1839 the current display (e.g., the background color from a web page). You |
|
1840 need to tell libpng whether the color is in the gamma space of the |
|
1841 display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file |
|
1842 (PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one |
|
1843 that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't |
|
1844 know why anyone would use this, but it's here). |
|
1845 |
|
1846 To properly display PNG images on any kind of system, the application needs |
|
1847 to know what the display gamma is. Ideally, the user will know this, and |
|
1848 the application will allow them to set it. One method of allowing the user |
|
1849 to set the display gamma separately for each system is to check for a |
|
1850 SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be |
|
1851 correctly set. |
|
1852 |
|
1853 Note that display_gamma is the overall gamma correction required to produce |
|
1854 pleasing results, which depends on the lighting conditions in the surrounding |
|
1855 environment. In a dim or brightly lit room, no compensation other than |
|
1856 the physical gamma exponent of the monitor is needed, while in a dark room |
|
1857 a slightly smaller exponent is better. |
|
1858 |
|
1859 double gamma, screen_gamma; |
|
1860 |
|
1861 if (/* We have a user-defined screen |
|
1862 gamma value */) |
|
1863 { |
|
1864 screen_gamma = user_defined_screen_gamma; |
|
1865 } |
|
1866 /* One way that applications can share the same |
|
1867 screen gamma value */ |
|
1868 else if ((gamma_str = getenv("SCREEN_GAMMA")) |
|
1869 != NULL) |
|
1870 { |
|
1871 screen_gamma = (double)atof(gamma_str); |
|
1872 } |
|
1873 /* If we don't have another value */ |
|
1874 else |
|
1875 { |
|
1876 screen_gamma = 2.2; /* A good guess for a |
|
1877 PC monitor in a bright office or a dim room */ |
|
1878 screen_gamma = 2.0; /* A good guess for a |
|
1879 PC monitor in a dark room */ |
|
1880 screen_gamma = 1.7 or 1.0; /* A good |
|
1881 guess for Mac systems */ |
|
1882 } |
|
1883 |
|
1884 The png_set_gamma() function handles gamma transformations of the data. |
|
1885 Pass both the file gamma and the current screen_gamma. If the file does |
|
1886 not have a gamma value, you can pass one anyway if you have an idea what |
|
1887 it is (usually 0.45455 is a good guess for GIF images on PCs). Note |
|
1888 that file gammas are inverted from screen gammas. See the discussions |
|
1889 on gamma in the PNG specification for an excellent description of what |
|
1890 gamma is, and why all applications should support it. It is strongly |
|
1891 recommended that PNG viewers support gamma correction. |
|
1892 |
|
1893 if (png_get_gAMA(png_ptr, info_ptr, &gamma)) |
|
1894 png_set_gamma(png_ptr, screen_gamma, gamma); |
|
1895 else |
|
1896 png_set_gamma(png_ptr, screen_gamma, 0.45455); |
|
1897 |
|
1898 If you need to reduce an RGB file to a paletted file, or if a paletted |
|
1899 file has more entries then will fit on your screen, png_set_dither() |
|
1900 will do that. Note that this is a simple match dither that merely |
|
1901 finds the closest color available. This should work fairly well with |
|
1902 optimized palettes, and fairly badly with linear color cubes. If you |
|
1903 pass a palette that is larger then maximum_colors, the file will |
|
1904 reduce the number of colors in the palette so it will fit into |
|
1905 maximum_colors. If there is a histogram, it will use it to make |
|
1906 more intelligent choices when reducing the palette. If there is no |
|
1907 histogram, it may not do as good a job. |
|
1908 |
|
1909 if (color_type & PNG_COLOR_MASK_COLOR) |
|
1910 { |
|
1911 if (png_get_valid(png_ptr, info_ptr, |
|
1912 PNG_INFO_PLTE)) |
|
1913 { |
|
1914 png_uint_16p histogram = NULL; |
|
1915 |
|
1916 png_get_hIST(png_ptr, info_ptr, |
|
1917 &histogram); |
|
1918 png_set_dither(png_ptr, palette, num_palette, |
|
1919 max_screen_colors, histogram, 1); |
|
1920 } |
|
1921 else |
|
1922 { |
|
1923 png_color std_color_cube[MAX_SCREEN_COLORS] = |
|
1924 { ... colors ... }; |
|
1925 |
|
1926 png_set_dither(png_ptr, std_color_cube, |
|
1927 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, |
|
1928 NULL,0); |
|
1929 } |
|
1930 } |
|
1931 |
|
1932 PNG files describe monochrome as black being zero and white being one. |
|
1933 The following code will reverse this (make black be one and white be |
|
1934 zero): |
|
1935 |
|
1936 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY) |
|
1937 png_set_invert_mono(png_ptr); |
|
1938 |
|
1939 This function can also be used to invert grayscale and gray-alpha images: |
|
1940 |
|
1941 if (color_type == PNG_COLOR_TYPE_GRAY || |
|
1942 color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
|
1943 png_set_invert_mono(png_ptr); |
|
1944 |
|
1945 PNG files store 16 bit pixels in network byte order (big-endian, |
|
1946 ie. most significant bits first). This code changes the storage to the |
|
1947 other way (little-endian, i.e. least significant bits first, the |
|
1948 way PCs store them): |
|
1949 |
|
1950 if (bit_depth == 16) |
|
1951 png_set_swap(png_ptr); |
|
1952 |
|
1953 If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you |
|
1954 need to change the order the pixels are packed into bytes, you can use: |
|
1955 |
|
1956 if (bit_depth < 8) |
|
1957 png_set_packswap(png_ptr); |
|
1958 |
|
1959 Finally, you can write your own transformation function if none of |
|
1960 the existing ones meets your needs. This is done by setting a callback |
|
1961 with |
|
1962 |
|
1963 png_set_read_user_transform_fn(png_ptr, |
|
1964 read_transform_fn); |
|
1965 |
|
1966 You must supply the function |
|
1967 |
|
1968 void read_transform_fn(png_ptr ptr, row_info_ptr |
|
1969 row_info, png_bytep data) |
|
1970 |
|
1971 See pngtest.c for a working example. Your function will be called |
|
1972 after all of the other transformations have been processed. |
|
1973 |
|
1974 You can also set up a pointer to a user structure for use by your |
|
1975 callback function, and you can inform libpng that your transform |
|
1976 function will change the number of channels or bit depth with the |
|
1977 function |
|
1978 |
|
1979 png_set_user_transform_info(png_ptr, user_ptr, |
|
1980 user_depth, user_channels); |
|
1981 |
|
1982 The user's application, not libpng, is responsible for allocating and |
|
1983 freeing any memory required for the user structure. |
|
1984 |
|
1985 You can retrieve the pointer via the function |
|
1986 png_get_user_transform_ptr(). For example: |
|
1987 |
|
1988 voidp read_user_transform_ptr = |
|
1989 png_get_user_transform_ptr(png_ptr); |
|
1990 |
|
1991 The last thing to handle is interlacing; this is covered in detail below, |
|
1992 but you must call the function here if you want libpng to handle expansion |
|
1993 of the interlaced image. |
|
1994 |
|
1995 number_of_passes = png_set_interlace_handling(png_ptr); |
|
1996 |
|
1997 After setting the transformations, libpng can update your png_info |
|
1998 structure to reflect any transformations you've requested with this |
|
1999 call. This is most useful to update the info structure's rowbytes |
|
2000 field so you can use it to allocate your image memory. This function |
|
2001 will also update your palette with the correct screen_gamma and |
|
2002 background if these have been given with the calls above. |
|
2003 |
|
2004 png_read_update_info(png_ptr, info_ptr); |
|
2005 |
|
2006 After you call png_read_update_info(), you can allocate any |
|
2007 memory you need to hold the image. The row data is simply |
|
2008 raw byte data for all forms of images. As the actual allocation |
|
2009 varies among applications, no example will be given. If you |
|
2010 are allocating one large chunk, you will need to build an |
|
2011 array of pointers to each row, as it will be needed for some |
|
2012 of the functions below. |
|
2013 |
|
2014 .SS Reading image data |
|
2015 |
|
2016 After you've allocated memory, you can read the image data. |
|
2017 The simplest way to do this is in one function call. If you are |
|
2018 allocating enough memory to hold the whole image, you can just |
|
2019 call png_read_image() and libpng will read in all the image data |
|
2020 and put it in the memory area supplied. You will need to pass in |
|
2021 an array of pointers to each row. |
|
2022 |
|
2023 This function automatically handles interlacing, so you don't need |
|
2024 to call png_set_interlace_handling() or call this function multiple |
|
2025 times, or any of that other stuff necessary with png_read_rows(). |
|
2026 |
|
2027 png_read_image(png_ptr, row_pointers); |
|
2028 |
|
2029 where row_pointers is: |
|
2030 |
|
2031 png_bytep row_pointers[height]; |
|
2032 |
|
2033 You can point to void or char or whatever you use for pixels. |
|
2034 |
|
2035 If you don't want to read in the whole image at once, you can |
|
2036 use png_read_rows() instead. If there is no interlacing (check |
|
2037 interlace_type == PNG_INTERLACE_NONE), this is simple: |
|
2038 |
|
2039 png_read_rows(png_ptr, row_pointers, NULL, |
|
2040 number_of_rows); |
|
2041 |
|
2042 where row_pointers is the same as in the png_read_image() call. |
|
2043 |
|
2044 If you are doing this just one row at a time, you can do this with |
|
2045 a single row_pointer instead of an array of row_pointers: |
|
2046 |
|
2047 png_bytep row_pointer = row; |
|
2048 png_read_row(png_ptr, row_pointer, NULL); |
|
2049 |
|
2050 If the file is interlaced (interlace_type != 0 in the IHDR chunk), things |
|
2051 get somewhat harder. The only current (PNG Specification version 1.2) |
|
2052 interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7) |
|
2053 is a somewhat complicated 2D interlace scheme, known as Adam7, that |
|
2054 breaks down an image into seven smaller images of varying size, based |
|
2055 on an 8x8 grid. |
|
2056 |
|
2057 libpng can fill out those images or it can give them to you "as is". |
|
2058 If you want them filled out, there are two ways to do that. The one |
|
2059 mentioned in the PNG specification is to expand each pixel to cover |
|
2060 those pixels that have not been read yet (the "rectangle" method). |
|
2061 This results in a blocky image for the first pass, which gradually |
|
2062 smooths out as more pixels are read. The other method is the "sparkle" |
|
2063 method, where pixels are drawn only in their final locations, with the |
|
2064 rest of the image remaining whatever colors they were initialized to |
|
2065 before the start of the read. The first method usually looks better, |
|
2066 but tends to be slower, as there are more pixels to put in the rows. |
|
2067 |
|
2068 If you don't want libpng to handle the interlacing details, just call |
|
2069 png_read_rows() seven times to read in all seven images. Each of the |
|
2070 images is a valid image by itself, or they can all be combined on an |
|
2071 8x8 grid to form a single image (although if you intend to combine them |
|
2072 you would be far better off using the libpng interlace handling). |
|
2073 |
|
2074 The first pass will return an image 1/8 as wide as the entire image |
|
2075 (every 8th column starting in column 0) and 1/8 as high as the original |
|
2076 (every 8th row starting in row 0), the second will be 1/8 as wide |
|
2077 (starting in column 4) and 1/8 as high (also starting in row 0). The |
|
2078 third pass will be 1/4 as wide (every 4th pixel starting in column 0) and |
|
2079 1/8 as high (every 8th row starting in row 4), and the fourth pass will |
|
2080 be 1/4 as wide and 1/4 as high (every 4th column starting in column 2, |
|
2081 and every 4th row starting in row 0). The fifth pass will return an |
|
2082 image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2), |
|
2083 while the sixth pass will be 1/2 as wide and 1/2 as high as the original |
|
2084 (starting in column 1 and row 0). The seventh and final pass will be as |
|
2085 wide as the original, and 1/2 as high, containing all of the odd |
|
2086 numbered scanlines. Phew! |
|
2087 |
|
2088 If you want libpng to expand the images, call this before calling |
|
2089 png_start_read_image() or png_read_update_info(): |
|
2090 |
|
2091 if (interlace_type == PNG_INTERLACE_ADAM7) |
|
2092 number_of_passes |
|
2093 = png_set_interlace_handling(png_ptr); |
|
2094 |
|
2095 This will return the number of passes needed. Currently, this |
|
2096 is seven, but may change if another interlace type is added. |
|
2097 This function can be called even if the file is not interlaced, |
|
2098 where it will return one pass. |
|
2099 |
|
2100 If you are not going to display the image after each pass, but are |
|
2101 going to wait until the entire image is read in, use the sparkle |
|
2102 effect. This effect is faster and the end result of either method |
|
2103 is exactly the same. If you are planning on displaying the image |
|
2104 after each pass, the "rectangle" effect is generally considered the |
|
2105 better looking one. |
|
2106 |
|
2107 If you only want the "sparkle" effect, just call png_read_rows() as |
|
2108 normal, with the third parameter NULL. Make sure you make pass over |
|
2109 the image number_of_passes times, and you don't change the data in the |
|
2110 rows between calls. You can change the locations of the data, just |
|
2111 not the data. Each pass only writes the pixels appropriate for that |
|
2112 pass, and assumes the data from previous passes is still valid. |
|
2113 |
|
2114 png_read_rows(png_ptr, row_pointers, NULL, |
|
2115 number_of_rows); |
|
2116 |
|
2117 If you only want the first effect (the rectangles), do the same as |
|
2118 before except pass the row buffer in the third parameter, and leave |
|
2119 the second parameter NULL. |
|
2120 |
|
2121 png_read_rows(png_ptr, NULL, row_pointers, |
|
2122 number_of_rows); |
|
2123 |
|
2124 .SS Finishing a sequential read |
|
2125 |
|
2126 After you are finished reading the image through the |
|
2127 low-level interface, you can finish reading the file. If you are |
|
2128 interested in comments or time, which may be stored either before or |
|
2129 after the image data, you should pass the separate png_info struct if |
|
2130 you want to keep the comments from before and after the image |
|
2131 separate. If you are not interested, you can pass NULL. |
|
2132 |
|
2133 png_read_end(png_ptr, end_info); |
|
2134 |
|
2135 When you are done, you can free all memory allocated by libpng like this: |
|
2136 |
|
2137 png_destroy_read_struct(&png_ptr, &info_ptr, |
|
2138 &end_info); |
|
2139 |
|
2140 It is also possible to individually free the info_ptr members that |
|
2141 point to libpng-allocated storage with the following function: |
|
2142 |
|
2143 png_free_data(png_ptr, info_ptr, mask, seq) |
|
2144 mask - identifies data to be freed, a mask |
|
2145 containing the bitwise OR of one or |
|
2146 more of |
|
2147 PNG_FREE_PLTE, PNG_FREE_TRNS, |
|
2148 PNG_FREE_HIST, PNG_FREE_ICCP, |
|
2149 PNG_FREE_PCAL, PNG_FREE_ROWS, |
|
2150 PNG_FREE_SCAL, PNG_FREE_SPLT, |
|
2151 PNG_FREE_TEXT, PNG_FREE_UNKN, |
|
2152 or simply PNG_FREE_ALL |
|
2153 seq - sequence number of item to be freed |
|
2154 (-1 for all items) |
|
2155 |
|
2156 This function may be safely called when the relevant storage has |
|
2157 already been freed, or has not yet been allocated, or was allocated |
|
2158 by the user and not by libpng, and will in those |
|
2159 cases do nothing. The "seq" parameter is ignored if only one item |
|
2160 of the selected data type, such as PLTE, is allowed. If "seq" is not |
|
2161 -1, and multiple items are allowed for the data type identified in |
|
2162 the mask, such as text or sPLT, only the n'th item in the structure |
|
2163 is freed, where n is "seq". |
|
2164 |
|
2165 The default behavior is only to free data that was allocated internally |
|
2166 by libpng. This can be changed, so that libpng will not free the data, |
|
2167 or so that it will free data that was allocated by the user with png_malloc() |
|
2168 or png_zalloc() and passed in via a png_set_*() function, with |
|
2169 |
|
2170 png_data_freer(png_ptr, info_ptr, freer, mask) |
|
2171 mask - which data elements are affected |
|
2172 same choices as in png_free_data() |
|
2173 freer - one of |
|
2174 PNG_DESTROY_WILL_FREE_DATA |
|
2175 PNG_SET_WILL_FREE_DATA |
|
2176 PNG_USER_WILL_FREE_DATA |
|
2177 |
|
2178 This function only affects data that has already been allocated. |
|
2179 You can call this function after reading the PNG data but before calling |
|
2180 any png_set_*() functions, to control whether the user or the png_set_*() |
|
2181 function is responsible for freeing any existing data that might be present, |
|
2182 and again after the png_set_*() functions to control whether the user |
|
2183 or png_destroy_*() is supposed to free the data. When the user assumes |
|
2184 responsibility for libpng-allocated data, the application must use |
|
2185 png_free() to free it, and when the user transfers responsibility to libpng |
|
2186 for data that the user has allocated, the user must have used png_malloc() |
|
2187 or png_zalloc() to allocate it. |
|
2188 |
|
2189 If you allocated your row_pointers in a single block, as suggested above in |
|
2190 the description of the high level read interface, you must not transfer |
|
2191 responsibility for freeing it to the png_set_rows or png_read_destroy function, |
|
2192 because they would also try to free the individual row_pointers[i]. |
|
2193 |
|
2194 If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword |
|
2195 separately, do not transfer responsibility for freeing text_ptr to libpng, |
|
2196 because when libpng fills a png_text structure it combines these members with |
|
2197 the key member, and png_free_data() will free only text_ptr.key. Similarly, |
|
2198 if you transfer responsibility for free'ing text_ptr from libpng to your |
|
2199 application, your application must not separately free those members. |
|
2200 |
|
2201 The png_free_data() function will turn off the "valid" flag for anything |
|
2202 it frees. If you need to turn the flag off for a chunk that was freed by your |
|
2203 application instead of by libpng, you can use |
|
2204 |
|
2205 png_set_invalid(png_ptr, info_ptr, mask); |
|
2206 mask - identifies the chunks to be made invalid, |
|
2207 containing the bitwise OR of one or |
|
2208 more of |
|
2209 PNG_INFO_gAMA, PNG_INFO_sBIT, |
|
2210 PNG_INFO_cHRM, PNG_INFO_PLTE, |
|
2211 PNG_INFO_tRNS, PNG_INFO_bKGD, |
|
2212 PNG_INFO_hIST, PNG_INFO_pHYs, |
|
2213 PNG_INFO_oFFs, PNG_INFO_tIME, |
|
2214 PNG_INFO_pCAL, PNG_INFO_sRGB, |
|
2215 PNG_INFO_iCCP, PNG_INFO_sPLT, |
|
2216 PNG_INFO_sCAL, PNG_INFO_IDAT |
|
2217 |
|
2218 For a more compact example of reading a PNG image, see the file example.c. |
|
2219 |
|
2220 .SS Reading PNG files progressively |
|
2221 |
|
2222 The progressive reader is slightly different then the non-progressive |
|
2223 reader. Instead of calling png_read_info(), png_read_rows(), and |
|
2224 png_read_end(), you make one call to png_process_data(), which calls |
|
2225 callbacks when it has the info, a row, or the end of the image. You |
|
2226 set up these callbacks with png_set_progressive_read_fn(). You don't |
|
2227 have to worry about the input/output functions of libpng, as you are |
|
2228 giving the library the data directly in png_process_data(). I will |
|
2229 assume that you have read the section on reading PNG files above, |
|
2230 so I will only highlight the differences (although I will show |
|
2231 all of the code). |
|
2232 |
|
2233 png_structp png_ptr; |
|
2234 png_infop info_ptr; |
|
2235 |
|
2236 /* An example code fragment of how you would |
|
2237 initialize the progressive reader in your |
|
2238 application. */ |
|
2239 int |
|
2240 initialize_png_reader() |
|
2241 { |
|
2242 png_ptr = png_create_read_struct |
|
2243 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
|
2244 user_error_fn, user_warning_fn); |
|
2245 if (!png_ptr) |
|
2246 return (ERROR); |
|
2247 info_ptr = png_create_info_struct(png_ptr); |
|
2248 if (!info_ptr) |
|
2249 { |
|
2250 png_destroy_read_struct(&png_ptr, (png_infopp)NULL, |
|
2251 (png_infopp)NULL); |
|
2252 return (ERROR); |
|
2253 } |
|
2254 |
|
2255 if (setjmp(png_jmpbuf(png_ptr))) |
|
2256 { |
|
2257 png_destroy_read_struct(&png_ptr, &info_ptr, |
|
2258 (png_infopp)NULL); |
|
2259 return (ERROR); |
|
2260 } |
|
2261 |
|
2262 /* This one's new. You can provide functions |
|
2263 to be called when the header info is valid, |
|
2264 when each row is completed, and when the image |
|
2265 is finished. If you aren't using all functions, |
|
2266 you can specify NULL parameters. Even when all |
|
2267 three functions are NULL, you need to call |
|
2268 png_set_progressive_read_fn(). You can use |
|
2269 any struct as the user_ptr (cast to a void pointer |
|
2270 for the function call), and retrieve the pointer |
|
2271 from inside the callbacks using the function |
|
2272 |
|
2273 png_get_progressive_ptr(png_ptr); |
|
2274 |
|
2275 which will return a void pointer, which you have |
|
2276 to cast appropriately. |
|
2277 */ |
|
2278 png_set_progressive_read_fn(png_ptr, (void *)user_ptr, |
|
2279 info_callback, row_callback, end_callback); |
|
2280 |
|
2281 return 0; |
|
2282 } |
|
2283 |
|
2284 /* A code fragment that you call as you receive blocks |
|
2285 of data */ |
|
2286 int |
|
2287 process_data(png_bytep buffer, png_uint_32 length) |
|
2288 { |
|
2289 if (setjmp(png_jmpbuf(png_ptr))) |
|
2290 { |
|
2291 png_destroy_read_struct(&png_ptr, &info_ptr, |
|
2292 (png_infopp)NULL); |
|
2293 return (ERROR); |
|
2294 } |
|
2295 |
|
2296 /* This one's new also. Simply give it a chunk |
|
2297 of data from the file stream (in order, of |
|
2298 course). On machines with segmented memory |
|
2299 models machines, don't give it any more than |
|
2300 64K. The library seems to run fine with sizes |
|
2301 of 4K. Although you can give it much less if |
|
2302 necessary (I assume you can give it chunks of |
|
2303 1 byte, I haven't tried less then 256 bytes |
|
2304 yet). When this function returns, you may |
|
2305 want to display any rows that were generated |
|
2306 in the row callback if you don't already do |
|
2307 so there. |
|
2308 */ |
|
2309 png_process_data(png_ptr, info_ptr, buffer, length); |
|
2310 return 0; |
|
2311 } |
|
2312 |
|
2313 /* This function is called (as set by |
|
2314 png_set_progressive_read_fn() above) when enough data |
|
2315 has been supplied so all of the header has been |
|
2316 read. |
|
2317 */ |
|
2318 void |
|
2319 info_callback(png_structp png_ptr, png_infop info) |
|
2320 { |
|
2321 /* Do any setup here, including setting any of |
|
2322 the transformations mentioned in the Reading |
|
2323 PNG files section. For now, you _must_ call |
|
2324 either png_start_read_image() or |
|
2325 png_read_update_info() after all the |
|
2326 transformations are set (even if you don't set |
|
2327 any). You may start getting rows before |
|
2328 png_process_data() returns, so this is your |
|
2329 last chance to prepare for that. |
|
2330 */ |
|
2331 } |
|
2332 |
|
2333 /* This function is called when each row of image |
|
2334 data is complete */ |
|
2335 void |
|
2336 row_callback(png_structp png_ptr, png_bytep new_row, |
|
2337 png_uint_32 row_num, int pass) |
|
2338 { |
|
2339 /* If the image is interlaced, and you turned |
|
2340 on the interlace handler, this function will |
|
2341 be called for every row in every pass. Some |
|
2342 of these rows will not be changed from the |
|
2343 previous pass. When the row is not changed, |
|
2344 the new_row variable will be NULL. The rows |
|
2345 and passes are called in order, so you don't |
|
2346 really need the row_num and pass, but I'm |
|
2347 supplying them because it may make your life |
|
2348 easier. |
|
2349 |
|
2350 For the non-NULL rows of interlaced images, |
|
2351 you must call png_progressive_combine_row() |
|
2352 passing in the row and the old row. You can |
|
2353 call this function for NULL rows (it will just |
|
2354 return) and for non-interlaced images (it just |
|
2355 does the memcpy for you) if it will make the |
|
2356 code easier. Thus, you can just do this for |
|
2357 all cases: |
|
2358 */ |
|
2359 |
|
2360 png_progressive_combine_row(png_ptr, old_row, |
|
2361 new_row); |
|
2362 |
|
2363 /* where old_row is what was displayed for |
|
2364 previously for the row. Note that the first |
|
2365 pass (pass == 0, really) will completely cover |
|
2366 the old row, so the rows do not have to be |
|
2367 initialized. After the first pass (and only |
|
2368 for interlaced images), you will have to pass |
|
2369 the current row, and the function will combine |
|
2370 the old row and the new row. |
|
2371 */ |
|
2372 } |
|
2373 |
|
2374 void |
|
2375 end_callback(png_structp png_ptr, png_infop info) |
|
2376 { |
|
2377 /* This function is called after the whole image |
|
2378 has been read, including any chunks after the |
|
2379 image (up to and including the IEND). You |
|
2380 will usually have the same info chunk as you |
|
2381 had in the header, although some data may have |
|
2382 been added to the comments and time fields. |
|
2383 |
|
2384 Most people won't do much here, perhaps setting |
|
2385 a flag that marks the image as finished. |
|
2386 */ |
|
2387 } |
|
2388 |
|
2389 |
|
2390 |
|
2391 .SH IV. Writing |
|
2392 |
|
2393 Much of this is very similar to reading. However, everything of |
|
2394 importance is repeated here, so you won't have to constantly look |
|
2395 back up in the reading section to understand writing. |
|
2396 |
|
2397 .SS Setup |
|
2398 |
|
2399 You will want to do the I/O initialization before you get into libpng, |
|
2400 so if it doesn't work, you don't have anything to undo. If you are not |
|
2401 using the standard I/O functions, you will need to replace them with |
|
2402 custom writing functions. See the discussion under Customizing libpng. |
|
2403 |
|
2404 FILE *fp = fopen(file_name, "wb"); |
|
2405 if (!fp) |
|
2406 { |
|
2407 return (ERROR); |
|
2408 } |
|
2409 |
|
2410 Next, png_struct and png_info need to be allocated and initialized. |
|
2411 As these can be both relatively large, you may not want to store these |
|
2412 on the stack, unless you have stack space to spare. Of course, you |
|
2413 will want to check if they return NULL. If you are also reading, |
|
2414 you won't want to name your read structure and your write structure |
|
2415 both "png_ptr"; you can call them anything you like, such as |
|
2416 "read_ptr" and "write_ptr". Look at pngtest.c, for example. |
|
2417 |
|
2418 png_structp png_ptr = png_create_write_struct |
|
2419 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
|
2420 user_error_fn, user_warning_fn); |
|
2421 if (!png_ptr) |
|
2422 return (ERROR); |
|
2423 |
|
2424 png_infop info_ptr = png_create_info_struct(png_ptr); |
|
2425 if (!info_ptr) |
|
2426 { |
|
2427 png_destroy_write_struct(&png_ptr, |
|
2428 (png_infopp)NULL); |
|
2429 return (ERROR); |
|
2430 } |
|
2431 |
|
2432 If you want to use your own memory allocation routines, |
|
2433 define PNG_USER_MEM_SUPPORTED and use |
|
2434 png_create_write_struct_2() instead of png_create_write_struct(): |
|
2435 |
|
2436 png_structp png_ptr = png_create_write_struct_2 |
|
2437 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
|
2438 user_error_fn, user_warning_fn, (png_voidp) |
|
2439 user_mem_ptr, user_malloc_fn, user_free_fn); |
|
2440 |
|
2441 After you have these structures, you will need to set up the |
|
2442 error handling. When libpng encounters an error, it expects to |
|
2443 longjmp() back to your routine. Therefore, you will need to call |
|
2444 setjmp() and pass the png_jmpbuf(png_ptr). If you |
|
2445 write the file from different routines, you will need to update |
|
2446 the png_jmpbuf(png_ptr) every time you enter a new routine that will |
|
2447 call a png_*() function. See your documentation of setjmp/longjmp |
|
2448 for your compiler for more information on setjmp/longjmp. See |
|
2449 the discussion on libpng error handling in the Customizing Libpng |
|
2450 section below for more information on the libpng error handling. |
|
2451 |
|
2452 if (setjmp(png_jmpbuf(png_ptr))) |
|
2453 { |
|
2454 png_destroy_write_struct(&png_ptr, &info_ptr); |
|
2455 fclose(fp); |
|
2456 return (ERROR); |
|
2457 } |
|
2458 ... |
|
2459 return; |
|
2460 |
|
2461 If you would rather avoid the complexity of setjmp/longjmp issues, |
|
2462 you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case |
|
2463 errors will result in a call to PNG_ABORT() which defaults to abort(). |
|
2464 |
|
2465 Now you need to set up the output code. The default for libpng is to |
|
2466 use the C function fwrite(). If you use this, you will need to pass a |
|
2467 valid FILE * in the function png_init_io(). Be sure that the file is |
|
2468 opened in binary mode. Again, if you wish to handle writing data in |
|
2469 another way, see the discussion on libpng I/O handling in the Customizing |
|
2470 Libpng section below. |
|
2471 |
|
2472 png_init_io(png_ptr, fp); |
|
2473 |
|
2474 If you are embedding your PNG into a datastream such as MNG, and don't |
|
2475 want libpng to write the 8-byte signature, or if you have already |
|
2476 written the signature in your application, use |
|
2477 |
|
2478 png_set_sig_bytes(png_ptr, 8); |
|
2479 |
|
2480 to inform libpng that it should not write a signature. |
|
2481 |
|
2482 .SS Write callbacks |
|
2483 |
|
2484 At this point, you can set up a callback function that will be |
|
2485 called after each row has been written, which you can use to control |
|
2486 a progress meter or the like. It's demonstrated in pngtest.c. |
|
2487 You must supply a function |
|
2488 |
|
2489 void write_row_callback(png_ptr, png_uint_32 row, |
|
2490 int pass); |
|
2491 { |
|
2492 /* put your code here */ |
|
2493 } |
|
2494 |
|
2495 (You can give it another name that you like instead of "write_row_callback") |
|
2496 |
|
2497 To inform libpng about your function, use |
|
2498 |
|
2499 png_set_write_status_fn(png_ptr, write_row_callback); |
|
2500 |
|
2501 You now have the option of modifying how the compression library will |
|
2502 run. The following functions are mainly for testing, but may be useful |
|
2503 in some cases, like if you need to write PNG files extremely fast and |
|
2504 are willing to give up some compression, or if you want to get the |
|
2505 maximum possible compression at the expense of slower writing. If you |
|
2506 have no special needs in this area, let the library do what it wants by |
|
2507 not calling this function at all, as it has been tuned to deliver a good |
|
2508 speed/compression ratio. The second parameter to png_set_filter() is |
|
2509 the filter method, for which the only valid values are 0 (as of the |
|
2510 July 1999 PNG specification, version 1.2) or 64 (if you are writing |
|
2511 a PNG datastream that is to be embedded in a MNG datastream). The third |
|
2512 parameter is a flag that indicates which filter type(s) are to be tested |
|
2513 for each scanline. See the PNG specification for details on the specific filter |
|
2514 types. |
|
2515 |
|
2516 |
|
2517 /* turn on or off filtering, and/or choose |
|
2518 specific filters. You can use either a single |
|
2519 PNG_FILTER_VALUE_NAME or the bitwise OR of one |
|
2520 or more PNG_FILTER_NAME masks. */ |
|
2521 png_set_filter(png_ptr, 0, |
|
2522 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | |
|
2523 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | |
|
2524 PNG_FILTER_UP | PNG_FILTER_VALUE_UP | |
|
2525 PNG_FILTER_AVE | PNG_FILTER_VALUE_AVE | |
|
2526 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| |
|
2527 PNG_ALL_FILTERS); |
|
2528 |
|
2529 If an application |
|
2530 wants to start and stop using particular filters during compression, |
|
2531 it should start out with all of the filters (to ensure that the previous |
|
2532 row of pixels will be stored in case it's needed later), and then add |
|
2533 and remove them after the start of compression. |
|
2534 |
|
2535 If you are writing a PNG datastream that is to be embedded in a MNG |
|
2536 datastream, the second parameter can be either 0 or 64. |
|
2537 |
|
2538 The png_set_compression_*() functions interface to the zlib compression |
|
2539 library, and should mostly be ignored unless you really know what you are |
|
2540 doing. The only generally useful call is png_set_compression_level() |
|
2541 which changes how much time zlib spends on trying to compress the image |
|
2542 data. See the Compression Library (zlib.h and algorithm.txt, distributed |
|
2543 with zlib) for details on the compression levels. |
|
2544 |
|
2545 /* set the zlib compression level */ |
|
2546 png_set_compression_level(png_ptr, |
|
2547 Z_BEST_COMPRESSION); |
|
2548 |
|
2549 /* set other zlib parameters */ |
|
2550 png_set_compression_mem_level(png_ptr, 8); |
|
2551 png_set_compression_strategy(png_ptr, |
|
2552 Z_DEFAULT_STRATEGY); |
|
2553 png_set_compression_window_bits(png_ptr, 15); |
|
2554 png_set_compression_method(png_ptr, 8); |
|
2555 png_set_compression_buffer_size(png_ptr, 8192) |
|
2556 |
|
2557 extern PNG_EXPORT(void,png_set_zbuf_size) |
|
2558 |
|
2559 .SS Setting the contents of info for output |
|
2560 |
|
2561 You now need to fill in the png_info structure with all the data you |
|
2562 wish to write before the actual image. Note that the only thing you |
|
2563 are allowed to write after the image is the text chunks and the time |
|
2564 chunk (as of PNG Specification 1.2, anyway). See png_write_end() and |
|
2565 the latest PNG specification for more information on that. If you |
|
2566 wish to write them before the image, fill them in now, and flag that |
|
2567 data as being valid. If you want to wait until after the data, don't |
|
2568 fill them until png_write_end(). For all the fields in png_info and |
|
2569 their data types, see png.h. For explanations of what the fields |
|
2570 contain, see the PNG specification. |
|
2571 |
|
2572 Some of the more important parts of the png_info are: |
|
2573 |
|
2574 png_set_IHDR(png_ptr, info_ptr, width, height, |
|
2575 bit_depth, color_type, interlace_type, |
|
2576 compression_type, filter_method) |
|
2577 width - holds the width of the image |
|
2578 in pixels (up to 2^31). |
|
2579 height - holds the height of the image |
|
2580 in pixels (up to 2^31). |
|
2581 bit_depth - holds the bit depth of one of the |
|
2582 image channels. |
|
2583 (valid values are 1, 2, 4, 8, 16 |
|
2584 and depend also on the |
|
2585 color_type. See also significant |
|
2586 bits (sBIT) below). |
|
2587 color_type - describes which color/alpha |
|
2588 channels are present. |
|
2589 PNG_COLOR_TYPE_GRAY |
|
2590 (bit depths 1, 2, 4, 8, 16) |
|
2591 PNG_COLOR_TYPE_GRAY_ALPHA |
|
2592 (bit depths 8, 16) |
|
2593 PNG_COLOR_TYPE_PALETTE |
|
2594 (bit depths 1, 2, 4, 8) |
|
2595 PNG_COLOR_TYPE_RGB |
|
2596 (bit_depths 8, 16) |
|
2597 PNG_COLOR_TYPE_RGB_ALPHA |
|
2598 (bit_depths 8, 16) |
|
2599 |
|
2600 PNG_COLOR_MASK_PALETTE |
|
2601 PNG_COLOR_MASK_COLOR |
|
2602 PNG_COLOR_MASK_ALPHA |
|
2603 |
|
2604 interlace_type - PNG_INTERLACE_NONE or |
|
2605 PNG_INTERLACE_ADAM7 |
|
2606 compression_type - (must be |
|
2607 PNG_COMPRESSION_TYPE_DEFAULT) |
|
2608 filter_method - (must be PNG_FILTER_TYPE_DEFAULT |
|
2609 or, if you are writing a PNG to |
|
2610 be embedded in a MNG datastream, |
|
2611 can also be |
|
2612 PNG_INTRAPIXEL_DIFFERENCING) |
|
2613 |
|
2614 If you call png_set_IHDR(), the call must appear before any of the |
|
2615 other png_set_*() functions, which might require access to some of |
|
2616 the IHDR settings. The remaining png_set_*() functions can be called |
|
2617 in any order. |
|
2618 |
|
2619 png_set_PLTE(png_ptr, info_ptr, palette, |
|
2620 num_palette); |
|
2621 palette - the palette for the file |
|
2622 (array of png_color) |
|
2623 num_palette - number of entries in the palette |
|
2624 |
|
2625 png_set_gAMA(png_ptr, info_ptr, gamma); |
|
2626 gamma - the gamma the image was created |
|
2627 at (PNG_INFO_gAMA) |
|
2628 |
|
2629 png_set_sRGB(png_ptr, info_ptr, srgb_intent); |
|
2630 srgb_intent - the rendering intent |
|
2631 (PNG_INFO_sRGB) The presence of |
|
2632 the sRGB chunk means that the pixel |
|
2633 data is in the sRGB color space. |
|
2634 This chunk also implies specific |
|
2635 values of gAMA and cHRM. Rendering |
|
2636 intent is the CSS-1 property that |
|
2637 has been defined by the International |
|
2638 Color Consortium |
|
2639 (http://www.color.org). |
|
2640 It can be one of |
|
2641 PNG_sRGB_INTENT_SATURATION, |
|
2642 PNG_sRGB_INTENT_PERCEPTUAL, |
|
2643 PNG_sRGB_INTENT_ABSOLUTE, or |
|
2644 PNG_sRGB_INTENT_RELATIVE. |
|
2645 |
|
2646 |
|
2647 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, |
|
2648 srgb_intent); |
|
2649 srgb_intent - the rendering intent |
|
2650 (PNG_INFO_sRGB) The presence of the |
|
2651 sRGB chunk means that the pixel |
|
2652 data is in the sRGB color space. |
|
2653 This function also causes gAMA and |
|
2654 cHRM chunks with the specific values |
|
2655 that are consistent with sRGB to be |
|
2656 written. |
|
2657 |
|
2658 png_set_iCCP(png_ptr, info_ptr, name, compression_type, |
|
2659 profile, proflen); |
|
2660 name - The profile name. |
|
2661 compression - The compression type; always |
|
2662 PNG_COMPRESSION_TYPE_BASE for PNG 1.0. |
|
2663 You may give NULL to this argument to |
|
2664 ignore it. |
|
2665 profile - International Color Consortium color |
|
2666 profile data. May contain NULs. |
|
2667 proflen - length of profile data in bytes. |
|
2668 |
|
2669 png_set_sBIT(png_ptr, info_ptr, sig_bit); |
|
2670 sig_bit - the number of significant bits for |
|
2671 (PNG_INFO_sBIT) each of the gray, red, |
|
2672 green, and blue channels, whichever are |
|
2673 appropriate for the given color type |
|
2674 (png_color_16) |
|
2675 |
|
2676 png_set_tRNS(png_ptr, info_ptr, trans, num_trans, |
|
2677 trans_values); |
|
2678 trans - array of transparent entries for |
|
2679 palette (PNG_INFO_tRNS) |
|
2680 trans_values - graylevel or color sample values of |
|
2681 the single transparent color for |
|
2682 non-paletted images (PNG_INFO_tRNS) |
|
2683 num_trans - number of transparent entries |
|
2684 (PNG_INFO_tRNS) |
|
2685 |
|
2686 png_set_hIST(png_ptr, info_ptr, hist); |
|
2687 (PNG_INFO_hIST) |
|
2688 hist - histogram of palette (array of |
|
2689 png_uint_16) |
|
2690 |
|
2691 png_set_tIME(png_ptr, info_ptr, mod_time); |
|
2692 mod_time - time image was last modified |
|
2693 (PNG_VALID_tIME) |
|
2694 |
|
2695 png_set_bKGD(png_ptr, info_ptr, background); |
|
2696 background - background color (PNG_VALID_bKGD) |
|
2697 |
|
2698 png_set_text(png_ptr, info_ptr, text_ptr, num_text); |
|
2699 text_ptr - array of png_text holding image |
|
2700 comments |
|
2701 text_ptr[i].compression - type of compression used |
|
2702 on "text" PNG_TEXT_COMPRESSION_NONE |
|
2703 PNG_TEXT_COMPRESSION_zTXt |
|
2704 PNG_ITXT_COMPRESSION_NONE |
|
2705 PNG_ITXT_COMPRESSION_zTXt |
|
2706 text_ptr[i].key - keyword for comment. Must contain |
|
2707 1-79 characters. |
|
2708 text_ptr[i].text - text comments for current |
|
2709 keyword. Can be NULL or empty. |
|
2710 text_ptr[i].text_length - length of text string, |
|
2711 after decompression, 0 for iTXt |
|
2712 text_ptr[i].itxt_length - length of itxt string, |
|
2713 after decompression, 0 for tEXt/zTXt |
|
2714 text_ptr[i].lang - language of comment (NULL or |
|
2715 empty for unknown). |
|
2716 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL |
|
2717 or empty for unknown). |
|
2718 num_text - number of comments |
|
2719 |
|
2720 png_set_sPLT(png_ptr, info_ptr, &palette_ptr, |
|
2721 num_spalettes); |
|
2722 palette_ptr - array of png_sPLT_struct structures |
|
2723 to be added to the list of palettes |
|
2724 in the info structure. |
|
2725 num_spalettes - number of palette structures to be |
|
2726 added. |
|
2727 |
|
2728 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, |
|
2729 unit_type); |
|
2730 offset_x - positive offset from the left |
|
2731 edge of the screen |
|
2732 offset_y - positive offset from the top |
|
2733 edge of the screen |
|
2734 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER |
|
2735 |
|
2736 png_set_pHYs(png_ptr, info_ptr, res_x, res_y, |
|
2737 unit_type); |
|
2738 res_x - pixels/unit physical resolution |
|
2739 in x direction |
|
2740 res_y - pixels/unit physical resolution |
|
2741 in y direction |
|
2742 unit_type - PNG_RESOLUTION_UNKNOWN, |
|
2743 PNG_RESOLUTION_METER |
|
2744 |
|
2745 png_set_sCAL(png_ptr, info_ptr, unit, width, height) |
|
2746 unit - physical scale units (an integer) |
|
2747 width - width of a pixel in physical scale units |
|
2748 height - height of a pixel in physical scale units |
|
2749 (width and height are doubles) |
|
2750 |
|
2751 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) |
|
2752 unit - physical scale units (an integer) |
|
2753 width - width of a pixel in physical scale units |
|
2754 height - height of a pixel in physical scale units |
|
2755 (width and height are strings like "2.54") |
|
2756 |
|
2757 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, |
|
2758 num_unknowns) |
|
2759 unknowns - array of png_unknown_chunk |
|
2760 structures holding unknown chunks |
|
2761 unknowns[i].name - name of unknown chunk |
|
2762 unknowns[i].data - data of unknown chunk |
|
2763 unknowns[i].size - size of unknown chunk's data |
|
2764 unknowns[i].location - position to write chunk in file |
|
2765 0: do not write chunk |
|
2766 PNG_HAVE_IHDR: before PLTE |
|
2767 PNG_HAVE_PLTE: before IDAT |
|
2768 PNG_AFTER_IDAT: after IDAT |
|
2769 |
|
2770 The "location" member is set automatically according to |
|
2771 what part of the output file has already been written. |
|
2772 You can change its value after calling png_set_unknown_chunks() |
|
2773 as demonstrated in pngtest.c. Within each of the "locations", |
|
2774 the chunks are sequenced according to their position in the |
|
2775 structure (that is, the value of "i", which is the order in which |
|
2776 the chunk was either read from the input file or defined with |
|
2777 png_set_unknown_chunks). |
|
2778 |
|
2779 A quick word about text and num_text. text is an array of png_text |
|
2780 structures. num_text is the number of valid structures in the array. |
|
2781 Each png_text structure holds a language code, a keyword, a text value, |
|
2782 and a compression type. |
|
2783 |
|
2784 The compression types have the same valid numbers as the compression |
|
2785 types of the image data. Currently, the only valid number is zero. |
|
2786 However, you can store text either compressed or uncompressed, unlike |
|
2787 images, which always have to be compressed. So if you don't want the |
|
2788 text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE. |
|
2789 Because tEXt and zTXt chunks don't have a language field, if you |
|
2790 specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt |
|
2791 any language code or translated keyword will not be written out. |
|
2792 |
|
2793 Until text gets around 1000 bytes, it is not worth compressing it. |
|
2794 After the text has been written out to the file, the compression type |
|
2795 is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, |
|
2796 so that it isn't written out again at the end (in case you are calling |
|
2797 png_write_end() with the same struct. |
|
2798 |
|
2799 The keywords that are given in the PNG Specification are: |
|
2800 |
|
2801 Title Short (one line) title or |
|
2802 caption for image |
|
2803 Author Name of image's creator |
|
2804 Description Description of image (possibly long) |
|
2805 Copyright Copyright notice |
|
2806 Creation Time Time of original image creation |
|
2807 (usually RFC 1123 format, see below) |
|
2808 Software Software used to create the image |
|
2809 Disclaimer Legal disclaimer |
|
2810 Warning Warning of nature of content |
|
2811 Source Device used to create the image |
|
2812 Comment Miscellaneous comment; conversion |
|
2813 from other image format |
|
2814 |
|
2815 The keyword-text pairs work like this. Keywords should be short |
|
2816 simple descriptions of what the comment is about. Some typical |
|
2817 keywords are found in the PNG specification, as is some recommendations |
|
2818 on keywords. You can repeat keywords in a file. You can even write |
|
2819 some text before the image and some after. For example, you may want |
|
2820 to put a description of the image before the image, but leave the |
|
2821 disclaimer until after, so viewers working over modem connections |
|
2822 don't have to wait for the disclaimer to go over the modem before |
|
2823 they start seeing the image. Finally, keywords should be full |
|
2824 words, not abbreviations. Keywords and text are in the ISO 8859-1 |
|
2825 (Latin-1) character set (a superset of regular ASCII) and can not |
|
2826 contain NUL characters, and should not contain control or other |
|
2827 unprintable characters. To make the comments widely readable, stick |
|
2828 with basic ASCII, and avoid machine specific character set extensions |
|
2829 like the IBM-PC character set. The keyword must be present, but |
|
2830 you can leave off the text string on non-compressed pairs. |
|
2831 Compressed pairs must have a text string, as only the text string |
|
2832 is compressed anyway, so the compression would be meaningless. |
|
2833 |
|
2834 PNG supports modification time via the png_time structure. Two |
|
2835 conversion routines are provided, png_convert_from_time_t() for |
|
2836 time_t and png_convert_from_struct_tm() for struct tm. The |
|
2837 time_t routine uses gmtime(). You don't have to use either of |
|
2838 these, but if you wish to fill in the png_time structure directly, |
|
2839 you should provide the time in universal time (GMT) if possible |
|
2840 instead of your local time. Note that the year number is the full |
|
2841 year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and |
|
2842 that months start with 1. |
|
2843 |
|
2844 If you want to store the time of the original image creation, you should |
|
2845 use a plain tEXt chunk with the "Creation Time" keyword. This is |
|
2846 necessary because the "creation time" of a PNG image is somewhat vague, |
|
2847 depending on whether you mean the PNG file, the time the image was |
|
2848 created in a non-PNG format, a still photo from which the image was |
|
2849 scanned, or possibly the subject matter itself. In order to facilitate |
|
2850 machine-readable dates, it is recommended that the "Creation Time" |
|
2851 tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"), |
|
2852 although this isn't a requirement. Unlike the tIME chunk, the |
|
2853 "Creation Time" tEXt chunk is not expected to be automatically changed |
|
2854 by the software. To facilitate the use of RFC 1123 dates, a function |
|
2855 png_convert_to_rfc1123(png_timep) is provided to convert from PNG |
|
2856 time to an RFC 1123 format string. |
|
2857 |
|
2858 .SS Writing unknown chunks |
|
2859 |
|
2860 You can use the png_set_unknown_chunks function to queue up chunks |
|
2861 for writing. You give it a chunk name, raw data, and a size; that's |
|
2862 all there is to it. The chunks will be written by the next following |
|
2863 png_write_info_before_PLTE, png_write_info, or png_write_end function. |
|
2864 Any chunks previously read into the info structure's unknown-chunk |
|
2865 list will also be written out in a sequence that satisfies the PNG |
|
2866 specification's ordering rules. |
|
2867 |
|
2868 .SS The high-level write interface |
|
2869 |
|
2870 At this point there are two ways to proceed; through the high-level |
|
2871 write interface, or through a sequence of low-level write operations. |
|
2872 You can use the high-level interface if your image data is present |
|
2873 in the info structure. All defined output |
|
2874 transformations are permitted, enabled by the following masks. |
|
2875 |
|
2876 PNG_TRANSFORM_IDENTITY No transformation |
|
2877 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples |
|
2878 PNG_TRANSFORM_PACKSWAP Change order of packed |
|
2879 pixels to LSB first |
|
2880 PNG_TRANSFORM_INVERT_MONO Invert monochrome images |
|
2881 PNG_TRANSFORM_SHIFT Normalize pixels to the |
|
2882 sBIT depth |
|
2883 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA |
|
2884 to BGRA |
|
2885 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA |
|
2886 to AG |
|
2887 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity |
|
2888 to transparency |
|
2889 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples |
|
2890 PNG_TRANSFORM_STRIP_FILLER Strip out filler bytes. |
|
2891 |
|
2892 If you have valid image data in the info structure (you can use |
|
2893 png_set_rows() to put image data in the info structure), simply do this: |
|
2894 |
|
2895 png_write_png(png_ptr, info_ptr, png_transforms, NULL) |
|
2896 |
|
2897 where png_transforms is an integer containing the bitwise OR of some set of |
|
2898 transformation flags. This call is equivalent to png_write_info(), |
|
2899 followed the set of transformations indicated by the transform mask, |
|
2900 then png_write_image(), and finally png_write_end(). |
|
2901 |
|
2902 (The final parameter of this call is not yet used. Someday it might point |
|
2903 to transformation parameters required by some future output transform.) |
|
2904 |
|
2905 You must use png_transforms and not call any png_set_transform() functions |
|
2906 when you use png_write_png(). |
|
2907 |
|
2908 .SS The low-level write interface |
|
2909 |
|
2910 If you are going the low-level route instead, you are now ready to |
|
2911 write all the file information up to the actual image data. You do |
|
2912 this with a call to png_write_info(). |
|
2913 |
|
2914 png_write_info(png_ptr, info_ptr); |
|
2915 |
|
2916 Note that there is one transformation you may need to do before |
|
2917 png_write_info(). In PNG files, the alpha channel in an image is the |
|
2918 level of opacity. If your data is supplied as a level of |
|
2919 transparency, you can invert the alpha channel before you write it, so |
|
2920 that 0 is fully transparent and 255 (in 8-bit or paletted images) or |
|
2921 65535 (in 16-bit images) is fully opaque, with |
|
2922 |
|
2923 png_set_invert_alpha(png_ptr); |
|
2924 |
|
2925 This must appear before png_write_info() instead of later with the |
|
2926 other transformations because in the case of paletted images the tRNS |
|
2927 chunk data has to be inverted before the tRNS chunk is written. If |
|
2928 your image is not a paletted image, the tRNS data (which in such cases |
|
2929 represents a single color to be rendered as transparent) won't need to |
|
2930 be changed, and you can safely do this transformation after your |
|
2931 png_write_info() call. |
|
2932 |
|
2933 If you need to write a private chunk that you want to appear before |
|
2934 the PLTE chunk when PLTE is present, you can write the PNG info in |
|
2935 two steps, and insert code to write your own chunk between them: |
|
2936 |
|
2937 png_write_info_before_PLTE(png_ptr, info_ptr); |
|
2938 png_set_unknown_chunks(png_ptr, info_ptr, ...); |
|
2939 png_write_info(png_ptr, info_ptr); |
|
2940 |
|
2941 After you've written the file information, you can set up the library |
|
2942 to handle any special transformations of the image data. The various |
|
2943 ways to transform the data will be described in the order that they |
|
2944 should occur. This is important, as some of these change the color |
|
2945 type and/or bit depth of the data, and some others only work on |
|
2946 certain color types and bit depths. Even though each transformation |
|
2947 checks to see if it has data that it can do something with, you should |
|
2948 make sure to only enable a transformation if it will be valid for the |
|
2949 data. For example, don't swap red and blue on grayscale data. |
|
2950 |
|
2951 PNG files store RGB pixels packed into 3 or 6 bytes. This code tells |
|
2952 the library to strip input data that has 4 or 8 bytes per pixel down |
|
2953 to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2 |
|
2954 bytes per pixel). |
|
2955 |
|
2956 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); |
|
2957 |
|
2958 where the 0 is unused, and the location is either PNG_FILLER_BEFORE or |
|
2959 PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel |
|
2960 is stored XRGB or RGBX. |
|
2961 |
|
2962 PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as |
|
2963 they can, resulting in, for example, 8 pixels per byte for 1 bit files. |
|
2964 If the data is supplied at 1 pixel per byte, use this code, which will |
|
2965 correctly pack the pixels into a single byte: |
|
2966 |
|
2967 png_set_packing(png_ptr); |
|
2968 |
|
2969 PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your |
|
2970 data is of another bit depth, you can write an sBIT chunk into the |
|
2971 file so that decoders can recover the original data if desired. |
|
2972 |
|
2973 /* Set the true bit depth of the image data */ |
|
2974 if (color_type & PNG_COLOR_MASK_COLOR) |
|
2975 { |
|
2976 sig_bit.red = true_bit_depth; |
|
2977 sig_bit.green = true_bit_depth; |
|
2978 sig_bit.blue = true_bit_depth; |
|
2979 } |
|
2980 else |
|
2981 { |
|
2982 sig_bit.gray = true_bit_depth; |
|
2983 } |
|
2984 if (color_type & PNG_COLOR_MASK_ALPHA) |
|
2985 { |
|
2986 sig_bit.alpha = true_bit_depth; |
|
2987 } |
|
2988 |
|
2989 png_set_sBIT(png_ptr, info_ptr, &sig_bit); |
|
2990 |
|
2991 If the data is stored in the row buffer in a bit depth other than |
|
2992 one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG), |
|
2993 this will scale the values to appear to be the correct bit depth as |
|
2994 is required by PNG. |
|
2995 |
|
2996 png_set_shift(png_ptr, &sig_bit); |
|
2997 |
|
2998 PNG files store 16 bit pixels in network byte order (big-endian, |
|
2999 ie. most significant bits first). This code would be used if they are |
|
3000 supplied the other way (little-endian, i.e. least significant bits |
|
3001 first, the way PCs store them): |
|
3002 |
|
3003 if (bit_depth > 8) |
|
3004 png_set_swap(png_ptr); |
|
3005 |
|
3006 If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you |
|
3007 need to change the order the pixels are packed into bytes, you can use: |
|
3008 |
|
3009 if (bit_depth < 8) |
|
3010 png_set_packswap(png_ptr); |
|
3011 |
|
3012 PNG files store 3 color pixels in red, green, blue order. This code |
|
3013 would be used if they are supplied as blue, green, red: |
|
3014 |
|
3015 png_set_bgr(png_ptr); |
|
3016 |
|
3017 PNG files describe monochrome as black being zero and white being |
|
3018 one. This code would be used if the pixels are supplied with this reversed |
|
3019 (black being one and white being zero): |
|
3020 |
|
3021 png_set_invert_mono(png_ptr); |
|
3022 |
|
3023 Finally, you can write your own transformation function if none of |
|
3024 the existing ones meets your needs. This is done by setting a callback |
|
3025 with |
|
3026 |
|
3027 png_set_write_user_transform_fn(png_ptr, |
|
3028 write_transform_fn); |
|
3029 |
|
3030 You must supply the function |
|
3031 |
|
3032 void write_transform_fn(png_ptr ptr, row_info_ptr |
|
3033 row_info, png_bytep data) |
|
3034 |
|
3035 See pngtest.c for a working example. Your function will be called |
|
3036 before any of the other transformations are processed. |
|
3037 |
|
3038 You can also set up a pointer to a user structure for use by your |
|
3039 callback function. |
|
3040 |
|
3041 png_set_user_transform_info(png_ptr, user_ptr, 0, 0); |
|
3042 |
|
3043 The user_channels and user_depth parameters of this function are ignored |
|
3044 when writing; you can set them to zero as shown. |
|
3045 |
|
3046 You can retrieve the pointer via the function png_get_user_transform_ptr(). |
|
3047 For example: |
|
3048 |
|
3049 voidp write_user_transform_ptr = |
|
3050 png_get_user_transform_ptr(png_ptr); |
|
3051 |
|
3052 It is possible to have libpng flush any pending output, either manually, |
|
3053 or automatically after a certain number of lines have been written. To |
|
3054 flush the output stream a single time call: |
|
3055 |
|
3056 png_write_flush(png_ptr); |
|
3057 |
|
3058 and to have libpng flush the output stream periodically after a certain |
|
3059 number of scanlines have been written, call: |
|
3060 |
|
3061 png_set_flush(png_ptr, nrows); |
|
3062 |
|
3063 Note that the distance between rows is from the last time png_write_flush() |
|
3064 was called, or the first row of the image if it has never been called. |
|
3065 So if you write 50 lines, and then png_set_flush 25, it will flush the |
|
3066 output on the next scanline, and every 25 lines thereafter, unless |
|
3067 png_write_flush() is called before 25 more lines have been written. |
|
3068 If nrows is too small (less than about 10 lines for a 640 pixel wide |
|
3069 RGB image) the image compression may decrease noticeably (although this |
|
3070 may be acceptable for real-time applications). Infrequent flushing will |
|
3071 only degrade the compression performance by a few percent over images |
|
3072 that do not use flushing. |
|
3073 |
|
3074 .SS Writing the image data |
|
3075 |
|
3076 That's it for the transformations. Now you can write the image data. |
|
3077 The simplest way to do this is in one function call. If you have the |
|
3078 whole image in memory, you can just call png_write_image() and libpng |
|
3079 will write the image. You will need to pass in an array of pointers to |
|
3080 each row. This function automatically handles interlacing, so you don't |
|
3081 need to call png_set_interlace_handling() or call this function multiple |
|
3082 times, or any of that other stuff necessary with png_write_rows(). |
|
3083 |
|
3084 png_write_image(png_ptr, row_pointers); |
|
3085 |
|
3086 where row_pointers is: |
|
3087 |
|
3088 png_byte *row_pointers[height]; |
|
3089 |
|
3090 You can point to void or char or whatever you use for pixels. |
|
3091 |
|
3092 If you don't want to write the whole image at once, you can |
|
3093 use png_write_rows() instead. If the file is not interlaced, |
|
3094 this is simple: |
|
3095 |
|
3096 png_write_rows(png_ptr, row_pointers, |
|
3097 number_of_rows); |
|
3098 |
|
3099 row_pointers is the same as in the png_write_image() call. |
|
3100 |
|
3101 If you are just writing one row at a time, you can do this with |
|
3102 a single row_pointer instead of an array of row_pointers: |
|
3103 |
|
3104 png_bytep row_pointer = row; |
|
3105 |
|
3106 png_write_row(png_ptr, row_pointer); |
|
3107 |
|
3108 When the file is interlaced, things can get a good deal more |
|
3109 complicated. The only currently (as of the PNG Specification |
|
3110 version 1.2, dated July 1999) defined interlacing scheme for PNG files |
|
3111 is the "Adam7" interlace scheme, that breaks down an |
|
3112 image into seven smaller images of varying size. libpng will build |
|
3113 these images for you, or you can do them yourself. If you want to |
|
3114 build them yourself, see the PNG specification for details of which |
|
3115 pixels to write when. |
|
3116 |
|
3117 If you don't want libpng to handle the interlacing details, just |
|
3118 use png_set_interlace_handling() and call png_write_rows() the |
|
3119 correct number of times to write all seven sub-images. |
|
3120 |
|
3121 If you want libpng to build the sub-images, call this before you start |
|
3122 writing any rows: |
|
3123 |
|
3124 number_of_passes = |
|
3125 png_set_interlace_handling(png_ptr); |
|
3126 |
|
3127 This will return the number of passes needed. Currently, this |
|
3128 is seven, but may change if another interlace type is added. |
|
3129 |
|
3130 Then write the complete image number_of_passes times. |
|
3131 |
|
3132 png_write_rows(png_ptr, row_pointers, |
|
3133 number_of_rows); |
|
3134 |
|
3135 As some of these rows are not used, and thus return immediately, |
|
3136 you may want to read about interlacing in the PNG specification, |
|
3137 and only update the rows that are actually used. |
|
3138 |
|
3139 .SS Finishing a sequential write |
|
3140 |
|
3141 After you are finished writing the image, you should finish writing |
|
3142 the file. If you are interested in writing comments or time, you should |
|
3143 pass an appropriately filled png_info pointer. If you are not interested, |
|
3144 you can pass NULL. |
|
3145 |
|
3146 png_write_end(png_ptr, info_ptr); |
|
3147 |
|
3148 When you are done, you can free all memory used by libpng like this: |
|
3149 |
|
3150 png_destroy_write_struct(&png_ptr, &info_ptr); |
|
3151 |
|
3152 It is also possible to individually free the info_ptr members that |
|
3153 point to libpng-allocated storage with the following function: |
|
3154 |
|
3155 png_free_data(png_ptr, info_ptr, mask, seq) |
|
3156 mask - identifies data to be freed, a mask |
|
3157 containing the bitwise OR of one or |
|
3158 more of |
|
3159 PNG_FREE_PLTE, PNG_FREE_TRNS, |
|
3160 PNG_FREE_HIST, PNG_FREE_ICCP, |
|
3161 PNG_FREE_PCAL, PNG_FREE_ROWS, |
|
3162 PNG_FREE_SCAL, PNG_FREE_SPLT, |
|
3163 PNG_FREE_TEXT, PNG_FREE_UNKN, |
|
3164 or simply PNG_FREE_ALL |
|
3165 seq - sequence number of item to be freed |
|
3166 (-1 for all items) |
|
3167 |
|
3168 This function may be safely called when the relevant storage has |
|
3169 already been freed, or has not yet been allocated, or was allocated |
|
3170 by the user and not by libpng, and will in those |
|
3171 cases do nothing. The "seq" parameter is ignored if only one item |
|
3172 of the selected data type, such as PLTE, is allowed. If "seq" is not |
|
3173 -1, and multiple items are allowed for the data type identified in |
|
3174 the mask, such as text or sPLT, only the n'th item in the structure |
|
3175 is freed, where n is "seq". |
|
3176 |
|
3177 If you allocated data such as a palette that you passed |
|
3178 in to libpng with png_set_*, you must not free it until just before the call to |
|
3179 png_destroy_write_struct(). |
|
3180 |
|
3181 The default behavior is only to free data that was allocated internally |
|
3182 by libpng. This can be changed, so that libpng will not free the data, |
|
3183 or so that it will free data that was allocated by the user with png_malloc() |
|
3184 or png_zalloc() and passed in via a png_set_*() function, with |
|
3185 |
|
3186 png_data_freer(png_ptr, info_ptr, freer, mask) |
|
3187 mask - which data elements are affected |
|
3188 same choices as in png_free_data() |
|
3189 freer - one of |
|
3190 PNG_DESTROY_WILL_FREE_DATA |
|
3191 PNG_SET_WILL_FREE_DATA |
|
3192 PNG_USER_WILL_FREE_DATA |
|
3193 |
|
3194 For example, to transfer responsibility for some data from a read structure |
|
3195 to a write structure, you could use |
|
3196 |
|
3197 png_data_freer(read_ptr, read_info_ptr, |
|
3198 PNG_USER_WILL_FREE_DATA, |
|
3199 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) |
|
3200 png_data_freer(write_ptr, write_info_ptr, |
|
3201 PNG_DESTROY_WILL_FREE_DATA, |
|
3202 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) |
|
3203 |
|
3204 thereby briefly reassigning responsibility for freeing to the user but |
|
3205 immediately afterwards reassigning it once more to the write_destroy |
|
3206 function. Having done this, it would then be safe to destroy the read |
|
3207 structure and continue to use the PLTE, tRNS, and hIST data in the write |
|
3208 structure. |
|
3209 |
|
3210 This function only affects data that has already been allocated. |
|
3211 You can call this function before calling after the png_set_*() functions |
|
3212 to control whether the user or png_destroy_*() is supposed to free the data. |
|
3213 When the user assumes responsibility for libpng-allocated data, the |
|
3214 application must use |
|
3215 png_free() to free it, and when the user transfers responsibility to libpng |
|
3216 for data that the user has allocated, the user must have used png_malloc() |
|
3217 or png_zalloc() to allocate it. |
|
3218 |
|
3219 If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword |
|
3220 separately, do not transfer responsibility for freeing text_ptr to libpng, |
|
3221 because when libpng fills a png_text structure it combines these members with |
|
3222 the key member, and png_free_data() will free only text_ptr.key. Similarly, |
|
3223 if you transfer responsibility for free'ing text_ptr from libpng to your |
|
3224 application, your application must not separately free those members. |
|
3225 For a more compact example of writing a PNG image, see the file example.c. |
|
3226 |
|
3227 .SH V. Modifying/Customizing libpng: |
|
3228 |
|
3229 There are two issues here. The first is changing how libpng does |
|
3230 standard things like memory allocation, input/output, and error handling. |
|
3231 The second deals with more complicated things like adding new chunks, |
|
3232 adding new transformations, and generally changing how libpng works. |
|
3233 Both of those are compile-time issues; that is, they are generally |
|
3234 determined at the time the code is written, and there is rarely a need |
|
3235 to provide the user with a means of changing them. |
|
3236 |
|
3237 Memory allocation, input/output, and error handling |
|
3238 |
|
3239 All of the memory allocation, input/output, and error handling in libpng |
|
3240 goes through callbacks that are user-settable. The default routines are |
|
3241 in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change |
|
3242 these functions, call the appropriate png_set_*_fn() function. |
|
3243 |
|
3244 Memory allocation is done through the functions png_malloc() |
|
3245 and png_free(). These currently just call the standard C functions. If |
|
3246 your pointers can't access more then 64K at a time, you will want to set |
|
3247 MAXSEG_64K in zlib.h. Since it is unlikely that the method of handling |
|
3248 memory allocation on a platform will change between applications, these |
|
3249 functions must be modified in the library at compile time. If you prefer |
|
3250 to use a different method of allocating and freeing data, you can use |
|
3251 png_create_read_struct_2() or png_create_write_struct_2() to register |
|
3252 your own functions as described above. |
|
3253 These functions also provide a void pointer that can be retrieved via |
|
3254 |
|
3255 mem_ptr=png_get_mem_ptr(png_ptr); |
|
3256 |
|
3257 Your replacement memory functions must have prototypes as follows: |
|
3258 |
|
3259 png_voidp malloc_fn(png_structp png_ptr, |
|
3260 png_size_t size); |
|
3261 void free_fn(png_structp png_ptr, png_voidp ptr); |
|
3262 |
|
3263 Your malloc_fn() must return NULL in case of failure. The png_malloc() |
|
3264 function will normally call png_error() if it receives a NULL from the |
|
3265 system memory allocator or from your replacement malloc_fn(). |
|
3266 |
|
3267 Your free_fn() will never be called with a NULL ptr, since libpng's |
|
3268 png_free() checks for NULL before calling free_fn(). |
|
3269 |
|
3270 Input/Output in libpng is done through png_read() and png_write(), |
|
3271 which currently just call fread() and fwrite(). The FILE * is stored in |
|
3272 png_struct and is initialized via png_init_io(). If you wish to change |
|
3273 the method of I/O, the library supplies callbacks that you can set |
|
3274 through the function png_set_read_fn() and png_set_write_fn() at run |
|
3275 time, instead of calling the png_init_io() function. These functions |
|
3276 also provide a void pointer that can be retrieved via the function |
|
3277 png_get_io_ptr(). For example: |
|
3278 |
|
3279 png_set_read_fn(png_structp read_ptr, |
|
3280 voidp read_io_ptr, png_rw_ptr read_data_fn) |
|
3281 |
|
3282 png_set_write_fn(png_structp write_ptr, |
|
3283 voidp write_io_ptr, png_rw_ptr write_data_fn, |
|
3284 png_flush_ptr output_flush_fn); |
|
3285 |
|
3286 voidp read_io_ptr = png_get_io_ptr(read_ptr); |
|
3287 voidp write_io_ptr = png_get_io_ptr(write_ptr); |
|
3288 |
|
3289 The replacement I/O functions must have prototypes as follows: |
|
3290 |
|
3291 void user_read_data(png_structp png_ptr, |
|
3292 png_bytep data, png_size_t length); |
|
3293 void user_write_data(png_structp png_ptr, |
|
3294 png_bytep data, png_size_t length); |
|
3295 void user_flush_data(png_structp png_ptr); |
|
3296 |
|
3297 Supplying NULL for the read, write, or flush functions sets them back |
|
3298 to using the default C stream functions. It is an error to read from |
|
3299 a write stream, and vice versa. |
|
3300 |
|
3301 Error handling in libpng is done through png_error() and png_warning(). |
|
3302 Errors handled through png_error() are fatal, meaning that png_error() |
|
3303 should never return to its caller. Currently, this is handled via |
|
3304 setjmp() and longjmp() (unless you have compiled libpng with |
|
3305 PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()), |
|
3306 but you could change this to do things like exit() if you should wish. |
|
3307 |
|
3308 On non-fatal errors, png_warning() is called |
|
3309 to print a warning message, and then control returns to the calling code. |
|
3310 By default png_error() and png_warning() print a message on stderr via |
|
3311 fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined |
|
3312 (because you don't want the messages) or PNG_NO_STDIO defined (because |
|
3313 fprintf() isn't available). If you wish to change the behavior of the error |
|
3314 functions, you will need to set up your own message callbacks. These |
|
3315 functions are normally supplied at the time that the png_struct is created. |
|
3316 It is also possible to redirect errors and warnings to your own replacement |
|
3317 functions after png_create_*_struct() has been called by calling: |
|
3318 |
|
3319 png_set_error_fn(png_structp png_ptr, |
|
3320 png_voidp error_ptr, png_error_ptr error_fn, |
|
3321 png_error_ptr warning_fn); |
|
3322 |
|
3323 png_voidp error_ptr = png_get_error_ptr(png_ptr); |
|
3324 |
|
3325 If NULL is supplied for either error_fn or warning_fn, then the libpng |
|
3326 default function will be used, calling fprintf() and/or longjmp() if a |
|
3327 problem is encountered. The replacement error functions should have |
|
3328 parameters as follows: |
|
3329 |
|
3330 void user_error_fn(png_structp png_ptr, |
|
3331 png_const_charp error_msg); |
|
3332 void user_warning_fn(png_structp png_ptr, |
|
3333 png_const_charp warning_msg); |
|
3334 |
|
3335 The motivation behind using setjmp() and longjmp() is the C++ throw and |
|
3336 catch exception handling methods. This makes the code much easier to write, |
|
3337 as there is no need to check every return code of every function call. |
|
3338 However, there are some uncertainties about the status of local variables |
|
3339 after a longjmp, so the user may want to be careful about doing anything after |
|
3340 setjmp returns non-zero besides returning itself. Consult your compiler |
|
3341 documentation for more details. For an alternative approach, you may wish |
|
3342 to use the "cexcept" facility (see http://cexcept.sourceforge.net). |
|
3343 |
|
3344 .SS Custom chunks |
|
3345 |
|
3346 If you need to read or write custom chunks, you may need to get deeper |
|
3347 into the libpng code. The library now has mechanisms for storing |
|
3348 and writing chunks of unknown type; you can even declare callbacks |
|
3349 for custom chunks. However, this may not be good enough if the |
|
3350 library code itself needs to know about interactions between your |
|
3351 chunk and existing `intrinsic' chunks. |
|
3352 |
|
3353 If you need to write a new intrinsic chunk, first read the PNG |
|
3354 specification. Acquire a first level of |
|
3355 understanding of how it works. Pay particular attention to the |
|
3356 sections that describe chunk names, and look at how other chunks were |
|
3357 designed, so you can do things similarly. Second, check out the |
|
3358 sections of libpng that read and write chunks. Try to find a chunk |
|
3359 that is similar to yours and use it as a template. More details can |
|
3360 be found in the comments inside the code. It is best to handle unknown |
|
3361 chunks in a generic method, via callback functions, instead of by |
|
3362 modifying libpng functions. |
|
3363 |
|
3364 If you wish to write your own transformation for the data, look through |
|
3365 the part of the code that does the transformations, and check out some of |
|
3366 the simpler ones to get an idea of how they work. Try to find a similar |
|
3367 transformation to the one you want to add and copy off of it. More details |
|
3368 can be found in the comments inside the code itself. |
|
3369 |
|
3370 .SS Configuring for 16 bit platforms |
|
3371 |
|
3372 You will want to look into zconf.h to tell zlib (and thus libpng) that |
|
3373 it cannot allocate more then 64K at a time. Even if you can, the memory |
|
3374 won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K. |
|
3375 |
|
3376 .SS Configuring for DOS |
|
3377 |
|
3378 For DOS users who only have access to the lower 640K, you will |
|
3379 have to limit zlib's memory usage via a png_set_compression_mem_level() |
|
3380 call. See zlib.h or zconf.h in the zlib library for more information. |
|
3381 |
|
3382 .SS Configuring for Medium Model |
|
3383 |
|
3384 Libpng's support for medium model has been tested on most of the popular |
|
3385 compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets |
|
3386 defined, and FAR gets defined to far in pngconf.h, and you should be |
|
3387 all set. Everything in the library (except for zlib's structure) is |
|
3388 expecting far data. You must use the typedefs with the p or pp on |
|
3389 the end for pointers (or at least look at them and be careful). Make |
|
3390 note that the rows of data are defined as png_bytepp, which is an |
|
3391 unsigned char far * far *. |
|
3392 |
|
3393 .SS Configuring for gui/windowing platforms: |
|
3394 |
|
3395 You will need to write new error and warning functions that use the GUI |
|
3396 interface, as described previously, and set them to be the error and |
|
3397 warning functions at the time that png_create_*_struct() is called, |
|
3398 in order to have them available during the structure initialization. |
|
3399 They can be changed later via png_set_error_fn(). On some compilers, |
|
3400 you may also have to change the memory allocators (png_malloc, etc.). |
|
3401 |
|
3402 .SS Configuring for compiler xxx: |
|
3403 |
|
3404 All includes for libpng are in pngconf.h. If you need to add/change/delete |
|
3405 an include, this is the place to do it. The includes that are not |
|
3406 needed outside libpng are protected by the PNG_INTERNAL definition, |
|
3407 which is only defined for those routines inside libpng itself. The |
|
3408 files in libpng proper only include png.h, which includes pngconf.h. |
|
3409 |
|
3410 .SS Configuring zlib: |
|
3411 |
|
3412 There are special functions to configure the compression. Perhaps the |
|
3413 most useful one changes the compression level, which currently uses |
|
3414 input compression values in the range 0 - 9. The library normally |
|
3415 uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests |
|
3416 have shown that for a large majority of images, compression values in |
|
3417 the range 3-6 compress nearly as well as higher levels, and do so much |
|
3418 faster. For online applications it may be desirable to have maximum speed |
|
3419 (Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also |
|
3420 specify no compression (Z_NO_COMPRESSION = 0), but this would create |
|
3421 files larger than just storing the raw bitmap. You can specify the |
|
3422 compression level by calling: |
|
3423 |
|
3424 png_set_compression_level(png_ptr, level); |
|
3425 |
|
3426 Another useful one is to reduce the memory level used by the library. |
|
3427 The memory level defaults to 8, but it can be lowered if you are |
|
3428 short on memory (running DOS, for example, where you only have 640K). |
|
3429 Note that the memory level does have an effect on compression; among |
|
3430 other things, lower levels will result in sections of incompressible |
|
3431 data being emitted in smaller stored blocks, with a correspondingly |
|
3432 larger relative overhead of up to 15% in the worst case. |
|
3433 |
|
3434 png_set_compression_mem_level(png_ptr, level); |
|
3435 |
|
3436 The other functions are for configuring zlib. They are not recommended |
|
3437 for normal use and may result in writing an invalid PNG file. See |
|
3438 zlib.h for more information on what these mean. |
|
3439 |
|
3440 png_set_compression_strategy(png_ptr, |
|
3441 strategy); |
|
3442 png_set_compression_window_bits(png_ptr, |
|
3443 window_bits); |
|
3444 png_set_compression_method(png_ptr, method); |
|
3445 png_set_compression_buffer_size(png_ptr, size); |
|
3446 |
|
3447 .SS Controlling row filtering |
|
3448 |
|
3449 If you want to control whether libpng uses filtering or not, which |
|
3450 filters are used, and how it goes about picking row filters, you |
|
3451 can call one of these functions. The selection and configuration |
|
3452 of row filters can have a significant impact on the size and |
|
3453 encoding speed and a somewhat lesser impact on the decoding speed |
|
3454 of an image. Filtering is enabled by default for RGB and grayscale |
|
3455 images (with and without alpha), but not for paletted images nor |
|
3456 for any images with bit depths less than 8 bits/pixel. |
|
3457 |
|
3458 The 'method' parameter sets the main filtering method, which is |
|
3459 currently only '0' in the PNG 1.2 specification. The 'filters' |
|
3460 parameter sets which filter(s), if any, should be used for each |
|
3461 scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS |
|
3462 to turn filtering on and off, respectively. |
|
3463 |
|
3464 Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB, |
|
3465 PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise |
|
3466 ORed together with '|' to specify one or more filters to use. |
|
3467 These filters are described in more detail in the PNG specification. |
|
3468 If you intend to change the filter type during the course of writing |
|
3469 the image, you should start with flags set for all of the filters |
|
3470 you intend to use so that libpng can initialize its internal |
|
3471 structures appropriately for all of the filter types. (Note that this |
|
3472 means the first row must always be adaptively filtered, because libpng |
|
3473 currently does not allocate the filter buffers until png_write_row() |
|
3474 is called for the first time.) |
|
3475 |
|
3476 filters = PNG_FILTER_NONE | PNG_FILTER_SUB |
|
3477 PNG_FILTER_UP | PNG_FILTER_AVE | |
|
3478 PNG_FILTER_PAETH | PNG_ALL_FILTERS; |
|
3479 |
|
3480 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, |
|
3481 filters); |
|
3482 The second parameter can also be |
|
3483 PNG_INTRAPIXEL_DIFFERENCING if you are |
|
3484 writing a PNG to be embedded in a MNG |
|
3485 datastream. This parameter must be the |
|
3486 same as the value of filter_method used |
|
3487 in png_set_IHDR(). |
|
3488 |
|
3489 It is also possible to influence how libpng chooses from among the |
|
3490 available filters. This is done in one or both of two ways - by |
|
3491 telling it how important it is to keep the same filter for successive |
|
3492 rows, and by telling it the relative computational costs of the filters. |
|
3493 |
|
3494 double weights[3] = {1.5, 1.3, 1.1}, |
|
3495 costs[PNG_FILTER_VALUE_LAST] = |
|
3496 {1.0, 1.3, 1.3, 1.5, 1.7}; |
|
3497 |
|
3498 png_set_filter_heuristics(png_ptr, |
|
3499 PNG_FILTER_HEURISTIC_WEIGHTED, 3, |
|
3500 weights, costs); |
|
3501 |
|
3502 The weights are multiplying factors that indicate to libpng that the |
|
3503 row filter should be the same for successive rows unless another row filter |
|
3504 is that many times better than the previous filter. In the above example, |
|
3505 if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a |
|
3506 "sum of absolute differences" 1.5 x 1.3 times higher than other filters |
|
3507 and still be chosen, while the NONE filter could have a sum 1.1 times |
|
3508 higher than other filters and still be chosen. Unspecified weights are |
|
3509 taken to be 1.0, and the specified weights should probably be declining |
|
3510 like those above in order to emphasize recent filters over older filters. |
|
3511 |
|
3512 The filter costs specify for each filter type a relative decoding cost |
|
3513 to be considered when selecting row filters. This means that filters |
|
3514 with higher costs are less likely to be chosen over filters with lower |
|
3515 costs, unless their "sum of absolute differences" is that much smaller. |
|
3516 The costs do not necessarily reflect the exact computational speeds of |
|
3517 the various filters, since this would unduly influence the final image |
|
3518 size. |
|
3519 |
|
3520 Note that the numbers above were invented purely for this example and |
|
3521 are given only to help explain the function usage. Little testing has |
|
3522 been done to find optimum values for either the costs or the weights. |
|
3523 |
|
3524 .SS Removing unwanted object code |
|
3525 |
|
3526 There are a bunch of #define's in pngconf.h that control what parts of |
|
3527 libpng are compiled. All the defines end in _SUPPORTED. If you are |
|
3528 never going to use a capability, you can change the #define to #undef |
|
3529 before recompiling libpng and save yourself code and data space, or |
|
3530 you can turn off individual capabilities with defines that begin with |
|
3531 PNG_NO_. |
|
3532 |
|
3533 You can also turn all of the transforms and ancillary chunk capabilities |
|
3534 off en masse with compiler directives that define |
|
3535 PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, |
|
3536 or all four, |
|
3537 along with directives to turn on any of the capabilities that you do |
|
3538 want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable |
|
3539 the extra transformations but still leave the library fully capable of reading |
|
3540 and writing PNG files with all known public chunks |
|
3541 Use of the PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive |
|
3542 produces a library that is incapable of reading or writing ancillary chunks. |
|
3543 If you are not using the progressive reading capability, you can |
|
3544 turn that off with PNG_NO_PROGRESSIVE_READ (don't confuse |
|
3545 this with the INTERLACING capability, which you'll still have). |
|
3546 |
|
3547 All the reading and writing specific code are in separate files, so the |
|
3548 linker should only grab the files it needs. However, if you want to |
|
3549 make sure, or if you are building a stand alone library, all the |
|
3550 reading files start with pngr and all the writing files start with |
|
3551 pngw. The files that don't match either (like png.c, pngtrans.c, etc.) |
|
3552 are used for both reading and writing, and always need to be included. |
|
3553 The progressive reader is in pngpread.c |
|
3554 |
|
3555 If you are creating or distributing a dynamically linked library (a .so |
|
3556 or DLL file), you should not remove or disable any parts of the library, |
|
3557 as this will cause applications linked with different versions of the |
|
3558 library to fail if they call functions not available in your library. |
|
3559 The size of the library itself should not be an issue, because only |
|
3560 those sections that are actually used will be loaded into memory. |
|
3561 |
|
3562 .SS Requesting debug printout |
|
3563 |
|
3564 The macro definition PNG_DEBUG can be used to request debugging |
|
3565 printout. Set it to an integer value in the range 0 to 3. Higher |
|
3566 numbers result in increasing amounts of debugging information. The |
|
3567 information is printed to the "stderr" file, unless another file |
|
3568 name is specified in the PNG_DEBUG_FILE macro definition. |
|
3569 |
|
3570 When PNG_DEBUG > 0, the following functions (macros) become available: |
|
3571 |
|
3572 png_debug(level, message) |
|
3573 png_debug1(level, message, p1) |
|
3574 png_debug2(level, message, p1, p2) |
|
3575 |
|
3576 in which "level" is compared to PNG_DEBUG to decide whether to print |
|
3577 the message, "message" is the formatted string to be printed, |
|
3578 and p1 and p2 are parameters that are to be embedded in the string |
|
3579 according to printf-style formatting directives. For example, |
|
3580 |
|
3581 png_debug1(2, "foo=%d\n", foo); |
|
3582 |
|
3583 is expanded to |
|
3584 |
|
3585 if(PNG_DEBUG > 2) |
|
3586 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); |
|
3587 |
|
3588 When PNG_DEBUG is defined but is zero, the macros aren't defined, but you |
|
3589 can still use PNG_DEBUG to control your own debugging: |
|
3590 |
|
3591 #ifdef PNG_DEBUG |
|
3592 fprintf(stderr, ... |
|
3593 #endif |
|
3594 |
|
3595 When PNG_DEBUG = 1, the macros are defined, but only png_debug statements |
|
3596 having level = 0 will be printed. There aren't any such statements in |
|
3597 this version of libpng, but if you insert some they will be printed. |
|
3598 |
|
3599 .SH VII. MNG support |
|
3600 |
|
3601 The MNG specification (available at http://www.libpng.org/pub/mng) allows |
|
3602 certain extensions to PNG for PNG images that are embedded in MNG datastreams. |
|
3603 Libpng can support some of these extensions. To enable them, use the |
|
3604 png_permit_mng_features() function: |
|
3605 |
|
3606 feature_set = png_permit_mng_features(png_ptr, mask) |
|
3607 mask is a png_uint_32 containing the bitwise OR of the |
|
3608 features you want to enable. These include |
|
3609 PNG_FLAG_MNG_EMPTY_PLTE |
|
3610 PNG_FLAG_MNG_FILTER_64 |
|
3611 PNG_ALL_MNG_FEATURES |
|
3612 feature_set is a png_uint_32 that is the bitwise AND of |
|
3613 your mask with the set of MNG features that is |
|
3614 supported by the version of libpng that you are using. |
|
3615 |
|
3616 It is an error to use this function when reading or writing a standalone |
|
3617 PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped |
|
3618 in a MNG datastream. As a minimum, it must have the MNG 8-byte signature |
|
3619 and the MHDR and MEND chunks. Libpng does not provide support for these |
|
3620 or any other MNG chunks; your application must provide its own support for |
|
3621 them. You may wish to consider using libmng (available at |
|
3622 http://www.libmng.com) instead. |
|
3623 |
|
3624 .SH VIII. Changes to Libpng from version 0.88 |
|
3625 |
|
3626 It should be noted that versions of libpng later than 0.96 are not |
|
3627 distributed by the original libpng author, Guy Schalnat, nor by |
|
3628 Andreas Dilger, who had taken over from Guy during 1996 and 1997, and |
|
3629 distributed versions 0.89 through 0.96, but rather by another member |
|
3630 of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are |
|
3631 still alive and well, but they have moved on to other things. |
|
3632 |
|
3633 The old libpng functions png_read_init(), png_write_init(), |
|
3634 png_info_init(), png_read_destroy(), and png_write_destroy() have been |
|
3635 moved to PNG_INTERNAL in version 0.95 to discourage their use. These |
|
3636 functions will be removed from libpng version 2.0.0. |
|
3637 |
|
3638 The preferred method of creating and initializing the libpng structures is |
|
3639 via the png_create_read_struct(), png_create_write_struct(), and |
|
3640 png_create_info_struct() because they isolate the size of the structures |
|
3641 from the application, allow version error checking, and also allow the |
|
3642 use of custom error handling routines during the initialization, which |
|
3643 the old functions do not. The functions png_read_destroy() and |
|
3644 png_write_destroy() do not actually free the memory that libpng |
|
3645 allocated for these structs, but just reset the data structures, so they |
|
3646 can be used instead of png_destroy_read_struct() and |
|
3647 png_destroy_write_struct() if you feel there is too much system overhead |
|
3648 allocating and freeing the png_struct for each image read. |
|
3649 |
|
3650 Setting the error callbacks via png_set_message_fn() before |
|
3651 png_read_init() as was suggested in libpng-0.88 is no longer supported |
|
3652 because this caused applications that do not use custom error functions |
|
3653 to fail if the png_ptr was not initialized to zero. It is still possible |
|
3654 to set the error callbacks AFTER png_read_init(), or to change them with |
|
3655 png_set_error_fn(), which is essentially the same function, but with a new |
|
3656 name to force compilation errors with applications that try to use the old |
|
3657 method. |
|
3658 |
|
3659 Starting with version 1.0.7, you can find out which version of the library |
|
3660 you are using at run-time: |
|
3661 |
|
3662 png_uint_32 libpng_vn = png_access_version_number(); |
|
3663 |
|
3664 The number libpng_vn is constructed from the major version, minor |
|
3665 version with leading zero, and release number with leading zero, |
|
3666 (e.g., libpng_vn for version 1.0.7 is 10007). |
|
3667 |
|
3668 You can also check which version of png.h you used when compiling your |
|
3669 application: |
|
3670 |
|
3671 png_uint_32 application_vn = PNG_LIBPNG_VER; |
|
3672 |
|
3673 .SH IX. Y2K Compliance in libpng |
|
3674 |
|
3675 September 18, 2008 |
|
3676 |
|
3677 Since the PNG Development group is an ad-hoc body, we can't make |
|
3678 an official declaration. |
|
3679 |
|
3680 This is your unofficial assurance that libpng from version 0.71 and |
|
3681 upward through 1.2.32 are Y2K compliant. It is my belief that earlier |
|
3682 versions were also Y2K compliant. |
|
3683 |
|
3684 Libpng only has three year fields. One is a 2-byte unsigned integer that |
|
3685 will hold years up to 65535. The other two hold the date in text |
|
3686 format, and will hold years up to 9999. |
|
3687 |
|
3688 The integer is |
|
3689 "png_uint_16 year" in png_time_struct. |
|
3690 |
|
3691 The strings are |
|
3692 "png_charp time_buffer" in png_struct and |
|
3693 "near_time_buffer", which is a local character string in png.c. |
|
3694 |
|
3695 There are seven time-related functions: |
|
3696 |
|
3697 png_convert_to_rfc_1123() in png.c |
|
3698 (formerly png_convert_to_rfc_1152() in error) |
|
3699 png_convert_from_struct_tm() in pngwrite.c, called |
|
3700 in pngwrite.c |
|
3701 png_convert_from_time_t() in pngwrite.c |
|
3702 png_get_tIME() in pngget.c |
|
3703 png_handle_tIME() in pngrutil.c, called in pngread.c |
|
3704 png_set_tIME() in pngset.c |
|
3705 png_write_tIME() in pngwutil.c, called in pngwrite.c |
|
3706 |
|
3707 All appear to handle dates properly in a Y2K environment. The |
|
3708 png_convert_from_time_t() function calls gmtime() to convert from system |
|
3709 clock time, which returns (year - 1900), which we properly convert to |
|
3710 the full 4-digit year. There is a possibility that applications using |
|
3711 libpng are not passing 4-digit years into the png_convert_to_rfc_1123() |
|
3712 function, or that they are incorrectly passing only a 2-digit year |
|
3713 instead of "year - 1900" into the png_convert_from_struct_tm() function, |
|
3714 but this is not under our control. The libpng documentation has always |
|
3715 stated that it works with 4-digit years, and the APIs have been |
|
3716 documented as such. |
|
3717 |
|
3718 The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned |
|
3719 integer to hold the year, and can hold years as large as 65535. |
|
3720 |
|
3721 zlib, upon which libpng depends, is also Y2K compliant. It contains |
|
3722 no date-related code. |
|
3723 |
|
3724 |
|
3725 Glenn Randers-Pehrson |
|
3726 libpng maintainer |
|
3727 PNG Development Group |
|
3728 |
|
3729 .SH NOTE |
|
3730 |
|
3731 Note about libpng version numbers: |
|
3732 |
|
3733 Due to various miscommunications, unforeseen code incompatibilities |
|
3734 and occasional factors outside the authors' control, version numbering |
|
3735 on the library has not always been consistent and straightforward. |
|
3736 The following table summarizes matters since version 0.89c, which was |
|
3737 the first widely used release: |
|
3738 |
|
3739 source png.h png.h shared-lib |
|
3740 version string int version |
|
3741 ------- ------ ----- ---------- |
|
3742 0.89c ("beta 3") 0.89 89 1.0.89 |
|
3743 0.90 ("beta 4") 0.90 90 0.90 |
|
3744 0.95 ("beta 5") 0.95 95 0.95 |
|
3745 0.96 ("beta 6") 0.96 96 0.96 |
|
3746 0.97b ("beta 7") 1.00.97 97 1.0.1 |
|
3747 0.97c 0.97 97 2.0.97 |
|
3748 0.98 0.98 98 2.0.98 |
|
3749 0.99 0.99 98 2.0.99 |
|
3750 0.99a-m 0.99 99 2.0.99 |
|
3751 1.00 1.00 100 2.1.0 |
|
3752 1.0.0 1.0.0 100 2.1.0 |
|
3753 1.0.0 (from here on, the 100 2.1.0 |
|
3754 1.0.1 png.h string is 10001 2.1.0 |
|
3755 1.0.1a-e identical to the 10002 from here on, the |
|
3756 1.0.2 source version) 10002 shared library is 2.V |
|
3757 1.0.2a-b 10003 where V is the source |
|
3758 1.0.1 10001 code version except as |
|
3759 1.0.1a-e 10002 2.1.0.1a-e noted. |
|
3760 1.0.2 10002 2.1.0.2 |
|
3761 1.0.2a-b 10003 2.1.0.2a-b |
|
3762 1.0.3 10003 2.1.0.3 |
|
3763 1.0.3a-d 10004 2.1.0.3a-d |
|
3764 1.0.4 10004 2.1.0.4 |
|
3765 1.0.4a-f 10005 2.1.0.4a-f |
|
3766 1.0.5 (+ 2 patches) 10005 2.1.0.5 |
|
3767 1.0.5a-d 10006 2.1.0.5a-d |
|
3768 1.0.5e-r 10100 2.1.0.5e-r |
|
3769 1.0.5s-v 10006 2.1.0.5s-v |
|
3770 1.0.6 (+ 3 patches) 10006 2.1.0.6 |
|
3771 1.0.6d-g 10007 2.1.0.6d-g |
|
3772 1.0.6h 10007 10.6h |
|
3773 1.0.6i 10007 10.6i |
|
3774 1.0.6j 10007 2.1.0.6j |
|
3775 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14 |
|
3776 1.0.7beta15-18 1 10007 2.1.0.7beta15-18 |
|
3777 1.0.7rc1-2 1 10007 2.1.0.7rc1-2 |
|
3778 1.0.7 1 10007 2.1.0.7 |
|
3779 1.0.8beta1-4 1 10008 2.1.0.8beta1-4 |
|
3780 1.0.8rc1 1 10008 2.1.0.8rc1 |
|
3781 1.0.8 1 10008 2.1.0.8 |
|
3782 1.0.9beta1-6 1 10009 2.1.0.9beta1-6 |
|
3783 1.0.9rc1 1 10009 2.1.0.9rc1 |
|
3784 1.0.9beta7-10 1 10009 2.1.0.9beta7-10 |
|
3785 1.0.9rc2 1 10009 2.1.0.9rc2 |
|
3786 1.0.9 1 10009 2.1.0.9 |
|
3787 1.0.10beta1 1 10010 2.1.0.10beta1 |
|
3788 1.0.10rc1 1 10010 2.1.0.10rc1 |
|
3789 1.0.10 1 10010 2.1.0.10 |
|
3790 1.0.11beta1-3 1 10011 2.1.0.11beta1-3 |
|
3791 1.0.11rc1 1 10011 2.1.0.11rc1 |
|
3792 1.0.11 1 10011 2.1.0.11 |
|
3793 1.0.12beta1-2 2 10012 2.1.0.12beta1-2 |
|
3794 1.0.12rc1 2 10012 2.1.0.12rc1 |
|
3795 1.0.12 2 10012 2.1.0.12 |
|
3796 1.1.0a-f - 10100 2.1.1.0a-f abandoned |
|
3797 1.2.0beta1-2 2 10200 2.1.2.0beta1-2 |
|
3798 1.2.0beta3-5 3 10200 3.1.2.0beta3-5 |
|
3799 1.2.0rc1 3 10200 3.1.2.0rc1 |
|
3800 1.2.0 3 10200 3.1.2.0 |
|
3801 1.2.1beta-4 3 10201 3.1.2.1beta1-4 |
|
3802 1.2.1rc1-2 3 10201 3.1.2.1rc1-2 |
|
3803 1.2.1 3 10201 3.1.2.1 |
|
3804 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6 |
|
3805 1.0.13beta1 10 10013 10.so.0.1.0.13beta1 |
|
3806 1.0.13rc1 10 10013 10.so.0.1.0.13rc1 |
|
3807 1.2.2rc1 12 10202 12.so.0.1.2.2rc1 |
|
3808 1.0.13 10 10013 10.so.0.1.0.13 |
|
3809 1.2.2 12 10202 12.so.0.1.2.2 |
|
3810 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6 |
|
3811 1.2.3 12 10203 12.so.0.1.2.3 |
|
3812 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3 |
|
3813 1.2.4rc1 13 10204 12.so.0.1.2.4rc1 |
|
3814 1.0.14 10 10014 10.so.0.1.0.14 |
|
3815 1.2.4 13 10204 12.so.0.1.2.4 |
|
3816 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2 |
|
3817 1.0.15rc1 10 10015 10.so.0.1.0.15rc1 |
|
3818 1.0.15 10 10015 10.so.0.1.0.15 |
|
3819 1.2.5 13 10205 12.so.0.1.2.5 |
|
3820 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4 |
|
3821 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5 |
|
3822 1.0.16 10 10016 10.so.0.1.0.16 |
|
3823 1.2.6 13 10206 12.so.0.1.2.6 |
|
3824 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2 |
|
3825 1.0.17rc1 10 10017 10.so.0.1.0.17rc1 |
|
3826 1.2.7rc1 13 10207 12.so.0.1.2.7rc1 |
|
3827 1.0.17 10 10017 10.so.0.1.0.17 |
|
3828 1.2.7 13 10207 12.so.0.1.2.7 |
|
3829 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5 |
|
3830 1.0.18rc1-5 10 10018 10.so.0.1.0.18rc1-5 |
|
3831 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5 |
|
3832 1.0.18 10 10018 10.so.0.1.0.18 |
|
3833 1.2.8 13 10208 12.so.0.1.2.8 |
|
3834 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3 |
|
3835 1.2.9beta4-11 13 10209 12.so.0.9[.0] |
|
3836 1.2.9rc1 13 10209 12.so.0.9[.0] |
|
3837 1.2.9 13 10209 12.so.0.9[.0] |
|
3838 1.2.10beta1-8 13 10210 12.so.0.10[.0] |
|
3839 1.2.10rc1-3 13 10210 12.so.0.10[.0] |
|
3840 1.2.10 13 10210 12.so.0.10[.0] |
|
3841 1.2.11beta1-4 13 10211 12.so.0.11[.0] |
|
3842 1.0.19rc1-5 10 10019 10.so.0.19[.0] |
|
3843 1.2.11rc1-5 13 10211 12.so.0.11[.0] |
|
3844 1.0.19 10 10019 10.so.0.19[.0] |
|
3845 1.2.11 13 10211 12.so.0.11[.0] |
|
3846 1.0.20 10 10020 10.so.0.20[.0] |
|
3847 1.2.12 13 10212 12.so.0.12[.0] |
|
3848 1.2.13beta1 13 10213 12.so.0.13[.0] |
|
3849 1.0.21 10 10021 10.so.0.21[.0] |
|
3850 1.2.13 13 10213 12.so.0.13[.0] |
|
3851 1.2.14beta1-2 13 10214 12.so.0.14[.0] |
|
3852 1.0.22rc1 10 10022 10.so.0.22[.0] |
|
3853 1.2.14rc1 13 10214 12.so.0.14[.0] |
|
3854 1.2.15beta1-6 13 10215 12.so.0.15[.0] |
|
3855 1.0.23rc1-5 10 10023 10.so.0.23[.0] |
|
3856 1.2.15rc1-5 13 10215 12.so.0.15[.0] |
|
3857 1.0.23 10 10023 10.so.0.23[.0] |
|
3858 1.2.15 13 10215 12.so.0.15[.0] |
|
3859 1.2.16beta1-2 13 10216 12.so.0.16[.0] |
|
3860 1.2.16rc1 13 10216 12.so.0.16[.0] |
|
3861 1.0.24 10 10024 10.so.0.24[.0] |
|
3862 1.2.16 13 10216 12.so.0.16[.0] |
|
3863 1.2.17beta1-2 13 10217 12.so.0.17[.0] |
|
3864 1.0.25rc1 10 10025 10.so.0.25[.0] |
|
3865 1.2.17rc1-3 13 10217 12.so.0.17[.0] |
|
3866 1.0.25 10 10025 10.so.0.25[.0] |
|
3867 1.2.17 13 10217 12.so.0.17[.0] |
|
3868 1.0.26 10 10026 10.so.0.26[.0] |
|
3869 1.2.18 13 10218 12.so.0.18[.0] |
|
3870 1.2.19beta1-31 13 10219 12.so.0.19[.0] |
|
3871 1.0.27rc1-6 10 10027 10.so.0.27[.0] |
|
3872 1.2.19rc1-6 13 10219 12.so.0.19[.0] |
|
3873 1.0.27 10 10027 10.so.0.27[.0] |
|
3874 1.2.19 13 10219 12.so.0.19[.0] |
|
3875 1.2.20beta01-04 13 10220 12.so.0.20[.0] |
|
3876 1.0.28rc1-6 10 10028 10.so.0.28[.0] |
|
3877 1.2.20rc1-6 13 10220 12.so.0.20[.0] |
|
3878 1.0.28 10 10028 10.so.0.28[.0] |
|
3879 1.2.20 13 10220 12.so.0.20[.0] |
|
3880 1.2.21beta1-2 13 10221 12.so.0.21[.0] |
|
3881 1.2.21rc1-3 13 10221 12.so.0.21[.0] |
|
3882 1.0.29 10 10029 10.so.0.29[.0] |
|
3883 1.2.21 13 10221 12.so.0.21[.0] |
|
3884 1.2.22beta1-4 13 10222 12.so.0.22[.0] |
|
3885 1.0.30rc1 13 10030 10.so.0.30[.0] |
|
3886 1.2.22rc1 13 10222 12.so.0.22[.0] |
|
3887 1.0.30 10 10030 10.so.0.30[.0] |
|
3888 1.2.22 13 10222 12.so.0.22[.0] |
|
3889 1.2.23beta01-05 13 10223 12.so.0.23[.0] |
|
3890 1.2.23rc01 13 10223 12.so.0.23[.0] |
|
3891 1.2.23 13 10223 12.so.0.23[.0] |
|
3892 1.2.24beta01-02 13 10224 12.so.0.24[.0] |
|
3893 1.2.24rc01 13 10224 12.so.0.24[.0] |
|
3894 1.2.24 13 10224 12.so.0.24[.0] |
|
3895 1.2.25beta01-06 13 10225 12.so.0.25[.0] |
|
3896 1.2.25rc01-02 13 10225 12.so.0.25[.0] |
|
3897 1.0.31 10 10031 10.so.0.31[.0] |
|
3898 1.2.25 13 10225 12.so.0.25[.0] |
|
3899 1.2.26beta01-06 13 10226 12.so.0.26[.0] |
|
3900 1.2.26rc01 13 10226 12.so.0.26[.0] |
|
3901 1.2.26 13 10226 12.so.0.26[.0] |
|
3902 1.0.32 10 10032 10.so.0.32[.0] |
|
3903 1.2.27beta01-06 13 10227 12.so.0.27[.0] |
|
3904 1.2.27rc01 13 10227 12.so.0.27[.0] |
|
3905 1.0.33 10 10033 10.so.0.33[.0] |
|
3906 1.2.27 13 10227 12.so.0.27[.0] |
|
3907 1.0.34 10 10034 10.so.0.34[.0] |
|
3908 1.2.28 13 10228 12.so.0.28[.0] |
|
3909 1.2.29beta01-03 13 10229 12.so.0.29[.0] |
|
3910 1.2.29rc01 13 10229 12.so.0.29[.0] |
|
3911 1.0.35 10 10035 10.so.0.35[.0] |
|
3912 1.2.29 13 10229 12.so.0.29[.0] |
|
3913 1.0.37 10 10037 10.so.0.37[.0] |
|
3914 1.2.30beta01-04 13 10230 12.so.0.30[.0] |
|
3915 1.0.38rc01-08 10 10038 10.so.0.38[.0] |
|
3916 1.2.30rc01-08 13 10230 12.so.0.30[.0] |
|
3917 1.0.38 10 10038 10.so.0.38[.0] |
|
3918 1.2.30 13 10230 12.so.0.30[.0] |
|
3919 1.0.39rc01-03 10 10039 10.so.0.39[.0] |
|
3920 1.2.31rc01-03 13 10231 12.so.0.31[.0] |
|
3921 1.0.39 10 10039 10.so.0.39[.0] |
|
3922 1.2.31 13 10231 12.so.0.31[.0] |
|
3923 1.2.32beta01-02 13 10232 12.so.0.32[.0] |
|
3924 1.0.40rc01 10 10040 10.so.0.40[.0] |
|
3925 1.2.32rc01 13 10232 12.so.0.32[.0] |
|
3926 1.0.40 10 10040 10.so.0.40[.0] |
|
3927 1.2.32 13 10232 12.so.0.32[.0] |
|
3928 |
|
3929 Henceforth the source version will match the shared-library minor |
|
3930 and patch numbers; the shared-library major version number will be |
|
3931 used for changes in backward compatibility, as it is intended. The |
|
3932 PNG_PNGLIB_VER macro, which is not used within libpng but is available |
|
3933 for applications, is an unsigned integer of the form xyyzz corresponding |
|
3934 to the source version x.y.z (leading zeros in y and z). Beta versions |
|
3935 were given the previous public release number plus a letter, until |
|
3936 version 1.0.6j; from then on they were given the upcoming public |
|
3937 release number plus "betaNN" or "rcN". |
|
3938 |
|
3939 .SH "SEE ALSO" |
|
3940 .IR libpngpf(3) ", " png(5) |
|
3941 .LP |
|
3942 .IR libpng : |
|
3943 .IP |
|
3944 http://libpng.sourceforge.net (follow the [DOWNLOAD] link) |
|
3945 http://www.libpng.org/pub/png |
|
3946 |
|
3947 .LP |
|
3948 .IR zlib : |
|
3949 .IP |
|
3950 (generally) at the same location as |
|
3951 .I libpng |
|
3952 or at |
|
3953 .br |
|
3954 ftp://ftp.info-zip.org/pub/infozip/zlib |
|
3955 |
|
3956 .LP |
|
3957 .IR PNG specification: RFC 2083 |
|
3958 .IP |
|
3959 (generally) at the same location as |
|
3960 .I libpng |
|
3961 or at |
|
3962 .br |
|
3963 ftp://ftp.rfc-editor.org:/in-notes/rfc2083.txt |
|
3964 .br |
|
3965 or (as a W3C Recommendation) at |
|
3966 .br |
|
3967 http://www.w3.org/TR/REC-png.html |
|
3968 |
|
3969 .LP |
|
3970 In the case of any inconsistency between the PNG specification |
|
3971 and this library, the specification takes precedence. |
|
3972 |
|
3973 .SH AUTHORS |
|
3974 This man page: Glenn Randers-Pehrson |
|
3975 <glennrp at users.sourceforge.net> |
|
3976 |
|
3977 The contributing authors would like to thank all those who helped |
|
3978 with testing, bug fixes, and patience. This wouldn't have been |
|
3979 possible without all of you. |
|
3980 |
|
3981 Thanks to Frank J. T. Wojcik for helping with the documentation. |
|
3982 |
|
3983 Libpng version 1.2.32 - September 18, 2008: |
|
3984 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. |
|
3985 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). |
|
3986 |
|
3987 Supported by the PNG development group |
|
3988 .br |
|
3989 png-mng-implement at lists.sf.net |
|
3990 (subscription required; visit |
|
3991 png-mng-implement at lists.sourceforge.net (subscription required; visit |
|
3992 https://lists.sourceforge.net/lists/listinfo/png-mng-implement |
|
3993 to subscribe). |
|
3994 |
|
3995 .SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE: |
|
3996 |
|
3997 (This copy of the libpng notices is provided for your convenience. In case of |
|
3998 any discrepancy between this copy and the notices in the file png.h that is |
|
3999 included in the libpng distribution, the latter shall prevail.) |
|
4000 |
|
4001 If you modify libpng you may insert additional notices immediately following |
|
4002 this sentence. |
|
4003 |
|
4004 libpng versions 1.2.6, August 15, 2004, through 1.2.32, September 18, 2008, are |
|
4005 Copyright (c) 2004,2006-2008 Glenn Randers-Pehrson, and are |
|
4006 distributed according to the same disclaimer and license as libpng-1.2.5 |
|
4007 with the following individual added to the list of Contributing Authors |
|
4008 |
|
4009 Cosmin Truta |
|
4010 |
|
4011 libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are |
|
4012 Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are |
|
4013 distributed according to the same disclaimer and license as libpng-1.0.6 |
|
4014 with the following individuals added to the list of Contributing Authors |
|
4015 |
|
4016 Simon-Pierre Cadieux |
|
4017 Eric S. Raymond |
|
4018 Gilles Vollant |
|
4019 |
|
4020 and with the following additions to the disclaimer: |
|
4021 |
|
4022 There is no warranty against interference with your |
|
4023 enjoyment of the library or against infringement. |
|
4024 There is no warranty that our efforts or the library |
|
4025 will fulfill any of your particular purposes or needs. |
|
4026 This library is provided with all faults, and the entire |
|
4027 risk of satisfactory quality, performance, accuracy, and |
|
4028 effort is with the user. |
|
4029 |
|
4030 libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are |
|
4031 Copyright (c) 1998, 1999 Glenn Randers-Pehrson |
|
4032 Distributed according to the same disclaimer and license as libpng-0.96, |
|
4033 with the following individuals added to the list of Contributing Authors: |
|
4034 |
|
4035 Tom Lane |
|
4036 Glenn Randers-Pehrson |
|
4037 Willem van Schaik |
|
4038 |
|
4039 libpng versions 0.89, June 1996, through 0.96, May 1997, are |
|
4040 Copyright (c) 1996, 1997 Andreas Dilger |
|
4041 Distributed according to the same disclaimer and license as libpng-0.88, |
|
4042 with the following individuals added to the list of Contributing Authors: |
|
4043 |
|
4044 John Bowler |
|
4045 Kevin Bracey |
|
4046 Sam Bushell |
|
4047 Magnus Holmgren |
|
4048 Greg Roelofs |
|
4049 Tom Tanner |
|
4050 |
|
4051 libpng versions 0.5, May 1995, through 0.88, January 1996, are |
|
4052 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
|
4053 |
|
4054 For the purposes of this copyright and license, "Contributing Authors" |
|
4055 is defined as the following set of individuals: |
|
4056 |
|
4057 Andreas Dilger |
|
4058 Dave Martindale |
|
4059 Guy Eric Schalnat |
|
4060 Paul Schmidt |
|
4061 Tim Wegner |
|
4062 |
|
4063 The PNG Reference Library is supplied "AS IS". The Contributing Authors |
|
4064 and Group 42, Inc. disclaim all warranties, expressed or implied, |
|
4065 including, without limitation, the warranties of merchantability and of |
|
4066 fitness for any purpose. The Contributing Authors and Group 42, Inc. |
|
4067 assume no liability for direct, indirect, incidental, special, exemplary, |
|
4068 or consequential damages, which may result from the use of the PNG |
|
4069 Reference Library, even if advised of the possibility of such damage. |
|
4070 |
|
4071 Permission is hereby granted to use, copy, modify, and distribute this |
|
4072 source code, or portions hereof, for any purpose, without fee, subject |
|
4073 to the following restrictions: |
|
4074 |
|
4075 1. The origin of this source code must not be misrepresented. |
|
4076 |
|
4077 2. Altered versions must be plainly marked as such and |
|
4078 must not be misrepresented as being the original source. |
|
4079 |
|
4080 3. This Copyright notice may not be removed or altered from |
|
4081 any source or altered source distribution. |
|
4082 |
|
4083 The Contributing Authors and Group 42, Inc. specifically permit, without |
|
4084 fee, and encourage the use of this source code as a component to |
|
4085 supporting the PNG file format in commercial products. If you use this |
|
4086 source code in a product, acknowledgment is not required but would be |
|
4087 appreciated. |
|
4088 |
|
4089 |
|
4090 A "png_get_copyright" function is available, for convenient use in "about" |
|
4091 boxes and the like: |
|
4092 |
|
4093 printf("%s",png_get_copyright(NULL)); |
|
4094 |
|
4095 Also, the PNG logo (in PNG format, of course) is supplied in the |
|
4096 files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31). |
|
4097 |
|
4098 Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a |
|
4099 certification mark of the Open Source Initiative. |
|
4100 |
|
4101 Glenn Randers-Pehrson |
|
4102 glennrp at users.sourceforge.net |
|
4103 September 18, 2008 |
|
4104 |
|
4105 .\" end of man page |
|
4106 |