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1 /* |
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2 * jccolor.c |
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3 * |
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4 * Copyright (C) 1991-1996, Thomas G. Lane. |
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5 * This file is part of the Independent JPEG Group's software. |
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6 * For conditions of distribution and use, see the accompanying README file. |
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7 * |
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8 * This file contains input colorspace conversion routines. |
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9 */ |
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10 |
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11 #define JPEG_INTERNALS |
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12 #include "jinclude.h" |
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13 #include "jpeglib.h" |
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14 |
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15 |
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16 /* Private subobject */ |
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17 |
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18 typedef struct { |
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19 struct jpeg_color_converter pub; /* public fields */ |
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20 |
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21 /* Private state for RGB->YCC conversion */ |
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22 INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */ |
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23 } my_color_converter; |
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24 |
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25 typedef my_color_converter * my_cconvert_ptr; |
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26 |
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27 |
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28 /**************** RGB -> YCbCr conversion: most common case **************/ |
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29 |
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30 /* |
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31 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are |
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32 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. |
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33 * The conversion equations to be implemented are therefore |
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34 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B |
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35 * Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE |
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36 * Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE |
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37 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) |
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38 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2, |
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39 * rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and |
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40 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0) |
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41 * were not represented exactly. Now we sacrifice exact representation of |
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42 * maximum red and maximum blue in order to get exact grayscales. |
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43 * |
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44 * To avoid floating-point arithmetic, we represent the fractional constants |
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45 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide |
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46 * the products by 2^16, with appropriate rounding, to get the correct answer. |
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47 * |
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48 * For even more speed, we avoid doing any multiplications in the inner loop |
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49 * by precalculating the constants times R,G,B for all possible values. |
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50 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); |
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51 * for 12-bit samples it is still acceptable. It's not very reasonable for |
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52 * 16-bit samples, but if you want lossless storage you shouldn't be changing |
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53 * colorspace anyway. |
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54 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included |
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55 * in the tables to save adding them separately in the inner loop. |
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56 */ |
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57 |
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58 #define SCALEBITS 16 /* speediest right-shift on some machines */ |
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59 #define CBCR_OFFSET ((INT32) CENTERJSAMPLE << SCALEBITS) |
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60 #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) |
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61 #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) |
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62 |
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63 /* We allocate one big table and divide it up into eight parts, instead of |
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64 * doing eight alloc_small requests. This lets us use a single table base |
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65 * address, which can be held in a register in the inner loops on many |
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66 * machines (more than can hold all eight addresses, anyway). |
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67 */ |
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68 |
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69 #define R_Y_OFF 0 /* offset to R => Y section */ |
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70 #define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */ |
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71 #define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */ |
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72 #define R_CB_OFF (3*(MAXJSAMPLE+1)) |
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73 #define G_CB_OFF (4*(MAXJSAMPLE+1)) |
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74 #define B_CB_OFF (5*(MAXJSAMPLE+1)) |
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75 #define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */ |
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76 #define G_CR_OFF (6*(MAXJSAMPLE+1)) |
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77 #define B_CR_OFF (7*(MAXJSAMPLE+1)) |
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78 #define TABLE_SIZE (8*(MAXJSAMPLE+1)) |
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79 |
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80 |
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81 /* |
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82 * Initialize for RGB->YCC colorspace conversion. |
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83 */ |
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84 |
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85 METHODDEF(void) |
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86 rgb_ycc_start (j_compress_ptr cinfo) |
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87 { |
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88 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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89 INT32 * rgb_ycc_tab; |
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90 INT32 i; |
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91 |
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92 /* Allocate and fill in the conversion tables. */ |
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93 cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) |
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94 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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95 (TABLE_SIZE * SIZEOF(INT32))); |
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96 |
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97 for (i = 0; i <= MAXJSAMPLE; i++) { |
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98 rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i; |
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99 rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i; |
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100 rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF; |
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101 rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i; |
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102 rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i; |
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103 /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. |
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104 * This ensures that the maximum output will round to MAXJSAMPLE |
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105 * not MAXJSAMPLE+1, and thus that we don't have to range-limit. |
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106 */ |
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107 rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; |
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108 /* B=>Cb and R=>Cr tables are the same |
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109 rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; |
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110 */ |
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111 rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i; |
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112 rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i; |
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113 } |
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114 } |
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115 |
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116 |
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117 /* |
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118 * Convert some rows of samples to the JPEG colorspace. |
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119 * |
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120 * Note that we change from the application's interleaved-pixel format |
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121 * to our internal noninterleaved, one-plane-per-component format. |
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122 * The input buffer is therefore three times as wide as the output buffer. |
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123 * |
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124 * A starting row offset is provided only for the output buffer. The caller |
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125 * can easily adjust the passed input_buf value to accommodate any row |
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126 * offset required on that side. |
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127 */ |
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128 |
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129 METHODDEF(void) |
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130 rgb_ycc_convert (j_compress_ptr cinfo, |
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131 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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132 JDIMENSION output_row, int num_rows) |
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133 { |
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134 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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135 register int r, g, b; |
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136 register INT32 * ctab = cconvert->rgb_ycc_tab; |
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137 register JSAMPROW inptr; |
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138 register JSAMPROW outptr0, outptr1, outptr2; |
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139 register JDIMENSION col; |
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140 JDIMENSION num_cols = cinfo->image_width; |
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141 |
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142 while (--num_rows >= 0) { |
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143 inptr = *input_buf++; |
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144 outptr0 = output_buf[0][output_row]; |
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145 outptr1 = output_buf[1][output_row]; |
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146 outptr2 = output_buf[2][output_row]; |
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147 output_row++; |
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148 for (col = 0; col < num_cols; col++) { |
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149 r = GETJSAMPLE(inptr[RGB_RED]); |
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150 g = GETJSAMPLE(inptr[RGB_GREEN]); |
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151 b = GETJSAMPLE(inptr[RGB_BLUE]); |
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152 inptr += RGB_PIXELSIZE; |
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153 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations |
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154 * must be too; we do not need an explicit range-limiting operation. |
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155 * Hence the value being shifted is never negative, and we don't |
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156 * need the general RIGHT_SHIFT macro. |
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157 */ |
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158 /* Y */ |
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159 outptr0[col] = (JSAMPLE) |
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160 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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161 >> SCALEBITS); |
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162 /* Cb */ |
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163 outptr1[col] = (JSAMPLE) |
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164 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) |
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165 >> SCALEBITS); |
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166 /* Cr */ |
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167 outptr2[col] = (JSAMPLE) |
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168 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) |
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169 >> SCALEBITS); |
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170 } |
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171 } |
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172 } |
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173 |
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174 |
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175 /**************** Cases other than RGB -> YCbCr **************/ |
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176 |
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177 |
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178 /* |
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179 * Convert some rows of samples to the JPEG colorspace. |
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180 * This version handles RGB->grayscale conversion, which is the same |
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181 * as the RGB->Y portion of RGB->YCbCr. |
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182 * We assume rgb_ycc_start has been called (we only use the Y tables). |
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183 */ |
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184 |
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185 METHODDEF(void) |
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186 rgb_gray_convert (j_compress_ptr cinfo, |
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187 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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188 JDIMENSION output_row, int num_rows) |
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189 { |
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190 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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191 register int r, g, b; |
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192 register INT32 * ctab = cconvert->rgb_ycc_tab; |
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193 register JSAMPROW inptr; |
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194 register JSAMPROW outptr; |
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195 register JDIMENSION col; |
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196 JDIMENSION num_cols = cinfo->image_width; |
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197 |
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198 while (--num_rows >= 0) { |
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199 inptr = *input_buf++; |
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200 outptr = output_buf[0][output_row]; |
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201 output_row++; |
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202 for (col = 0; col < num_cols; col++) { |
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203 r = GETJSAMPLE(inptr[RGB_RED]); |
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204 g = GETJSAMPLE(inptr[RGB_GREEN]); |
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205 b = GETJSAMPLE(inptr[RGB_BLUE]); |
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206 inptr += RGB_PIXELSIZE; |
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207 /* Y */ |
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208 outptr[col] = (JSAMPLE) |
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209 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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210 >> SCALEBITS); |
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211 } |
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212 } |
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213 } |
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214 |
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215 |
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216 /* |
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217 * Convert some rows of samples to the JPEG colorspace. |
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218 * This version handles Adobe-style CMYK->YCCK conversion, |
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219 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same |
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220 * conversion as above, while passing K (black) unchanged. |
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221 * We assume rgb_ycc_start has been called. |
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222 */ |
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223 |
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224 METHODDEF(void) |
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225 cmyk_ycck_convert (j_compress_ptr cinfo, |
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226 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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227 JDIMENSION output_row, int num_rows) |
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228 { |
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229 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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230 register int r, g, b; |
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231 register INT32 * ctab = cconvert->rgb_ycc_tab; |
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232 register JSAMPROW inptr; |
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233 register JSAMPROW outptr0, outptr1, outptr2, outptr3; |
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234 register JDIMENSION col; |
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235 JDIMENSION num_cols = cinfo->image_width; |
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236 |
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237 while (--num_rows >= 0) { |
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238 inptr = *input_buf++; |
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239 outptr0 = output_buf[0][output_row]; |
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240 outptr1 = output_buf[1][output_row]; |
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241 outptr2 = output_buf[2][output_row]; |
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242 outptr3 = output_buf[3][output_row]; |
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243 output_row++; |
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244 for (col = 0; col < num_cols; col++) { |
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245 r = MAXJSAMPLE - GETJSAMPLE(inptr[0]); |
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246 g = MAXJSAMPLE - GETJSAMPLE(inptr[1]); |
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247 b = MAXJSAMPLE - GETJSAMPLE(inptr[2]); |
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248 /* K passes through as-is */ |
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249 outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */ |
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250 inptr += 4; |
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251 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations |
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252 * must be too; we do not need an explicit range-limiting operation. |
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253 * Hence the value being shifted is never negative, and we don't |
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254 * need the general RIGHT_SHIFT macro. |
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255 */ |
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256 /* Y */ |
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257 outptr0[col] = (JSAMPLE) |
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258 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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259 >> SCALEBITS); |
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260 /* Cb */ |
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261 outptr1[col] = (JSAMPLE) |
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262 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) |
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263 >> SCALEBITS); |
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264 /* Cr */ |
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265 outptr2[col] = (JSAMPLE) |
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266 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) |
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267 >> SCALEBITS); |
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268 } |
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269 } |
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270 } |
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271 |
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272 |
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273 /* |
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274 * Convert some rows of samples to the JPEG colorspace. |
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275 * This version handles grayscale output with no conversion. |
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276 * The source can be either plain grayscale or YCbCr (since Y == gray). |
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277 */ |
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278 |
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279 METHODDEF(void) |
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280 grayscale_convert (j_compress_ptr cinfo, |
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281 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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282 JDIMENSION output_row, int num_rows) |
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283 { |
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284 register JSAMPROW inptr; |
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285 register JSAMPROW outptr; |
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286 register JDIMENSION col; |
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287 JDIMENSION num_cols = cinfo->image_width; |
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288 int instride = cinfo->input_components; |
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289 |
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290 while (--num_rows >= 0) { |
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291 inptr = *input_buf++; |
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292 outptr = output_buf[0][output_row]; |
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293 output_row++; |
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294 for (col = 0; col < num_cols; col++) { |
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295 outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */ |
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296 inptr += instride; |
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297 } |
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298 } |
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299 } |
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300 |
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301 |
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302 /* |
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303 * Convert some rows of samples to the JPEG colorspace. |
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304 * This version handles multi-component colorspaces without conversion. |
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305 * We assume input_components == num_components. |
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306 */ |
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307 |
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308 METHODDEF(void) |
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309 null_convert (j_compress_ptr cinfo, |
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310 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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311 JDIMENSION output_row, int num_rows) |
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312 { |
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313 register JSAMPROW inptr; |
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314 register JSAMPROW outptr; |
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315 register JDIMENSION col; |
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316 register int ci; |
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317 int nc = cinfo->num_components; |
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318 JDIMENSION num_cols = cinfo->image_width; |
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319 |
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320 while (--num_rows >= 0) { |
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321 /* It seems fastest to make a separate pass for each component. */ |
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322 for (ci = 0; ci < nc; ci++) { |
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323 inptr = *input_buf; |
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324 outptr = output_buf[ci][output_row]; |
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325 for (col = 0; col < num_cols; col++) { |
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326 outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */ |
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327 inptr += nc; |
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328 } |
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329 } |
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330 input_buf++; |
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331 output_row++; |
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332 } |
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333 } |
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334 |
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335 |
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336 /* |
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337 * Empty method for start_pass. |
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338 */ |
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339 |
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340 METHODDEF(void) |
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341 null_method (j_compress_ptr cinfo) |
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342 { |
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343 /* no work needed */ |
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344 } |
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345 |
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346 |
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347 /* |
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348 * Module initialization routine for input colorspace conversion. |
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349 */ |
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350 |
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351 GLOBAL(void) |
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352 jinit_color_converter (j_compress_ptr cinfo) |
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353 { |
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354 my_cconvert_ptr cconvert; |
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355 |
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356 cconvert = (my_cconvert_ptr) |
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357 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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358 SIZEOF(my_color_converter)); |
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359 cinfo->cconvert = (struct jpeg_color_converter *) cconvert; |
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360 /* set start_pass to null method until we find out differently */ |
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361 cconvert->pub.start_pass = null_method; |
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362 |
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363 /* Make sure input_components agrees with in_color_space */ |
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364 switch (cinfo->in_color_space) { |
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365 case JCS_GRAYSCALE: |
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366 if (cinfo->input_components != 1) |
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367 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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368 break; |
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369 |
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370 case JCS_RGB: |
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371 #if RGB_PIXELSIZE != 3 |
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372 if (cinfo->input_components != RGB_PIXELSIZE) |
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373 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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374 break; |
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375 #endif /* else share code with YCbCr */ |
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376 |
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377 case JCS_YCbCr: |
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378 if (cinfo->input_components != 3) |
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379 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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380 break; |
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381 |
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382 case JCS_CMYK: |
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383 case JCS_YCCK: |
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384 if (cinfo->input_components != 4) |
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385 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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386 break; |
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387 |
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388 default: /* JCS_UNKNOWN can be anything */ |
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389 if (cinfo->input_components < 1) |
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390 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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391 break; |
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392 } |
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393 |
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394 /* Check num_components, set conversion method based on requested space */ |
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395 switch (cinfo->jpeg_color_space) { |
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396 case JCS_GRAYSCALE: |
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397 if (cinfo->num_components != 1) |
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398 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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399 if (cinfo->in_color_space == JCS_GRAYSCALE) |
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400 cconvert->pub.color_convert = grayscale_convert; |
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401 else if (cinfo->in_color_space == JCS_RGB) { |
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402 cconvert->pub.start_pass = rgb_ycc_start; |
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403 cconvert->pub.color_convert = rgb_gray_convert; |
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404 } else if (cinfo->in_color_space == JCS_YCbCr) |
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405 cconvert->pub.color_convert = grayscale_convert; |
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406 else |
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407 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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408 break; |
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409 |
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410 case JCS_RGB: |
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411 if (cinfo->num_components != 3) |
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412 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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413 if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3) |
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414 cconvert->pub.color_convert = null_convert; |
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415 else |
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416 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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417 break; |
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418 |
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419 case JCS_YCbCr: |
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420 if (cinfo->num_components != 3) |
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421 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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422 if (cinfo->in_color_space == JCS_RGB) { |
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423 cconvert->pub.start_pass = rgb_ycc_start; |
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424 cconvert->pub.color_convert = rgb_ycc_convert; |
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425 } else if (cinfo->in_color_space == JCS_YCbCr) |
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426 cconvert->pub.color_convert = null_convert; |
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427 else |
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428 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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429 break; |
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430 |
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431 case JCS_CMYK: |
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432 if (cinfo->num_components != 4) |
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433 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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434 if (cinfo->in_color_space == JCS_CMYK) |
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435 cconvert->pub.color_convert = null_convert; |
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436 else |
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437 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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438 break; |
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439 |
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440 case JCS_YCCK: |
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441 if (cinfo->num_components != 4) |
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442 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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443 if (cinfo->in_color_space == JCS_CMYK) { |
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444 cconvert->pub.start_pass = rgb_ycc_start; |
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445 cconvert->pub.color_convert = cmyk_ycck_convert; |
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446 } else if (cinfo->in_color_space == JCS_YCCK) |
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447 cconvert->pub.color_convert = null_convert; |
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448 else |
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449 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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450 break; |
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451 |
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452 default: /* allow null conversion of JCS_UNKNOWN */ |
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453 if (cinfo->jpeg_color_space != cinfo->in_color_space || |
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454 cinfo->num_components != cinfo->input_components) |
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455 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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456 cconvert->pub.color_convert = null_convert; |
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457 break; |
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458 } |
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459 } |