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1 /* |
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2 * jquant1.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 1-pass color quantization (color mapping) routines. |
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9 * These routines provide mapping to a fixed color map using equally spaced |
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10 * color values. Optional Floyd-Steinberg or ordered dithering is available. |
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11 */ |
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12 |
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13 #define JPEG_INTERNALS |
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14 #include "jinclude.h" |
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15 #include "jpeglib.h" |
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16 |
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17 #ifdef QUANT_1PASS_SUPPORTED |
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18 |
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19 |
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20 /* |
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21 * The main purpose of 1-pass quantization is to provide a fast, if not very |
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22 * high quality, colormapped output capability. A 2-pass quantizer usually |
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23 * gives better visual quality; however, for quantized grayscale output this |
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24 * quantizer is perfectly adequate. Dithering is highly recommended with this |
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25 * quantizer, though you can turn it off if you really want to. |
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26 * |
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27 * In 1-pass quantization the colormap must be chosen in advance of seeing the |
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28 * image. We use a map consisting of all combinations of Ncolors[i] color |
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29 * values for the i'th component. The Ncolors[] values are chosen so that |
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30 * their product, the total number of colors, is no more than that requested. |
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31 * (In most cases, the product will be somewhat less.) |
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32 * |
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33 * Since the colormap is orthogonal, the representative value for each color |
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34 * component can be determined without considering the other components; |
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35 * then these indexes can be combined into a colormap index by a standard |
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36 * N-dimensional-array-subscript calculation. Most of the arithmetic involved |
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37 * can be precalculated and stored in the lookup table colorindex[]. |
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38 * colorindex[i][j] maps pixel value j in component i to the nearest |
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39 * representative value (grid plane) for that component; this index is |
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40 * multiplied by the array stride for component i, so that the |
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41 * index of the colormap entry closest to a given pixel value is just |
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42 * sum( colorindex[component-number][pixel-component-value] ) |
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43 * Aside from being fast, this scheme allows for variable spacing between |
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44 * representative values with no additional lookup cost. |
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45 * |
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46 * If gamma correction has been applied in color conversion, it might be wise |
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47 * to adjust the color grid spacing so that the representative colors are |
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48 * equidistant in linear space. At this writing, gamma correction is not |
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49 * implemented by jdcolor, so nothing is done here. |
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50 */ |
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51 |
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52 |
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53 /* Declarations for ordered dithering. |
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54 * |
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55 * We use a standard 16x16 ordered dither array. The basic concept of ordered |
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56 * dithering is described in many references, for instance Dale Schumacher's |
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57 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). |
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58 * In place of Schumacher's comparisons against a "threshold" value, we add a |
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59 * "dither" value to the input pixel and then round the result to the nearest |
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60 * output value. The dither value is equivalent to (0.5 - threshold) times |
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61 * the distance between output values. For ordered dithering, we assume that |
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62 * the output colors are equally spaced; if not, results will probably be |
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63 * worse, since the dither may be too much or too little at a given point. |
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64 * |
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65 * The normal calculation would be to form pixel value + dither, range-limit |
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66 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. |
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67 * We can skip the separate range-limiting step by extending the colorindex |
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68 * table in both directions. |
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69 */ |
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70 |
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71 #define ODITHER_SIZE 16 /* dimension of dither matrix */ |
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72 /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ |
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73 #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ |
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74 #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */ |
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75 |
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76 typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE]; |
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77 typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE]; |
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78 |
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79 static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = { |
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80 /* Bayer's order-4 dither array. Generated by the code given in |
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81 * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I. |
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82 * The values in this array must range from 0 to ODITHER_CELLS-1. |
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83 */ |
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84 { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 }, |
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85 { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 }, |
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86 { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 }, |
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87 { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 }, |
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88 { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 }, |
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89 { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 }, |
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90 { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 }, |
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91 { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 }, |
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92 { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 }, |
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93 { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 }, |
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94 { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 }, |
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95 { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 }, |
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96 { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 }, |
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97 { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 }, |
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98 { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 }, |
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99 { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 } |
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100 }; |
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101 |
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102 |
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103 /* Declarations for Floyd-Steinberg dithering. |
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104 * |
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105 * Errors are accumulated into the array fserrors[], at a resolution of |
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106 * 1/16th of a pixel count. The error at a given pixel is propagated |
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107 * to its not-yet-processed neighbors using the standard F-S fractions, |
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108 * ... (here) 7/16 |
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109 * 3/16 5/16 1/16 |
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110 * We work left-to-right on even rows, right-to-left on odd rows. |
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111 * |
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112 * We can get away with a single array (holding one row's worth of errors) |
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113 * by using it to store the current row's errors at pixel columns not yet |
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114 * processed, but the next row's errors at columns already processed. We |
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115 * need only a few extra variables to hold the errors immediately around the |
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116 * current column. (If we are lucky, those variables are in registers, but |
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117 * even if not, they're probably cheaper to access than array elements are.) |
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118 * |
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119 * The fserrors[] array is indexed [component#][position]. |
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120 * We provide (#columns + 2) entries per component; the extra entry at each |
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121 * end saves us from special-casing the first and last pixels. |
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122 * |
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123 * Note: on a wide image, we might not have enough room in a PC's near data |
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124 * segment to hold the error array; so it is allocated with alloc_large. |
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125 */ |
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126 |
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127 #if BITS_IN_JSAMPLE == 8 |
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128 typedef INT16 FSERROR; /* 16 bits should be enough */ |
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129 typedef int LOCFSERROR; /* use 'int' for calculation temps */ |
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130 #else |
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131 typedef INT32 FSERROR; /* may need more than 16 bits */ |
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132 typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */ |
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133 #endif |
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134 |
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135 typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */ |
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136 |
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137 |
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138 /* Private subobject */ |
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139 |
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140 #define MAX_Q_COMPS 4 /* max components I can handle */ |
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141 |
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142 typedef struct { |
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143 struct jpeg_color_quantizer pub; /* public fields */ |
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144 |
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145 /* Initially allocated colormap is saved here */ |
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146 JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ |
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147 int sv_actual; /* number of entries in use */ |
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148 |
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149 JSAMPARRAY colorindex; /* Precomputed mapping for speed */ |
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150 /* colorindex[i][j] = index of color closest to pixel value j in component i, |
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151 * premultiplied as described above. Since colormap indexes must fit into |
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152 * JSAMPLEs, the entries of this array will too. |
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153 */ |
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154 boolean is_padded; /* is the colorindex padded for odither? */ |
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155 |
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156 int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ |
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157 |
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158 /* Variables for ordered dithering */ |
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159 int row_index; /* cur row's vertical index in dither matrix */ |
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160 ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ |
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161 |
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162 /* Variables for Floyd-Steinberg dithering */ |
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163 FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ |
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164 boolean on_odd_row; /* flag to remember which row we are on */ |
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165 } my_cquantizer; |
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166 |
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167 typedef my_cquantizer * my_cquantize_ptr; |
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168 |
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169 |
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170 /* |
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171 * Policy-making subroutines for create_colormap and create_colorindex. |
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172 * These routines determine the colormap to be used. The rest of the module |
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173 * only assumes that the colormap is orthogonal. |
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174 * |
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175 * * select_ncolors decides how to divvy up the available colors |
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176 * among the components. |
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177 * * output_value defines the set of representative values for a component. |
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178 * * largest_input_value defines the mapping from input values to |
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179 * representative values for a component. |
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180 * Note that the latter two routines may impose different policies for |
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181 * different components, though this is not currently done. |
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182 */ |
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183 |
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184 |
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185 LOCAL(int) |
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186 select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) |
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187 /* Determine allocation of desired colors to components, */ |
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188 /* and fill in Ncolors[] array to indicate choice. */ |
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189 /* Return value is total number of colors (product of Ncolors[] values). */ |
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190 { |
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191 int nc = cinfo->out_color_components; /* number of color components */ |
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192 int max_colors = cinfo->desired_number_of_colors; |
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193 int total_colors, iroot, i, j; |
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194 boolean changed; |
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195 long temp; |
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196 static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; |
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197 |
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198 /* We can allocate at least the nc'th root of max_colors per component. */ |
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199 /* Compute floor(nc'th root of max_colors). */ |
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200 iroot = 1; |
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201 do { |
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202 iroot++; |
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203 temp = iroot; /* set temp = iroot ** nc */ |
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204 for (i = 1; i < nc; i++) |
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205 temp *= iroot; |
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206 } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */ |
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207 iroot--; /* now iroot = floor(root) */ |
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208 |
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209 /* Must have at least 2 color values per component */ |
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210 if (iroot < 2) |
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211 ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp); |
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212 |
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213 /* Initialize to iroot color values for each component */ |
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214 total_colors = 1; |
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215 for (i = 0; i < nc; i++) { |
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216 Ncolors[i] = iroot; |
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217 total_colors *= iroot; |
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218 } |
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219 /* We may be able to increment the count for one or more components without |
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220 * exceeding max_colors, though we know not all can be incremented. |
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221 * Sometimes, the first component can be incremented more than once! |
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222 * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.) |
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223 * In RGB colorspace, try to increment G first, then R, then B. |
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224 */ |
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225 do { |
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226 changed = FALSE; |
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227 for (i = 0; i < nc; i++) { |
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228 j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i); |
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229 /* calculate new total_colors if Ncolors[j] is incremented */ |
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230 temp = total_colors / Ncolors[j]; |
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231 temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */ |
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232 if (temp > (long) max_colors) |
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233 break; /* won't fit, done with this pass */ |
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234 Ncolors[j]++; /* OK, apply the increment */ |
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235 total_colors = (int) temp; |
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236 changed = TRUE; |
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237 } |
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238 } while (changed); |
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239 |
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240 return total_colors; |
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241 } |
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242 |
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243 |
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244 LOCAL(int) |
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245 output_value (j_decompress_ptr cinfo, int ci, int j, int maxj) |
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246 /* Return j'th output value, where j will range from 0 to maxj */ |
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247 /* The output values must fall in 0..MAXJSAMPLE in increasing order */ |
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248 { |
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249 /* We always provide values 0 and MAXJSAMPLE for each component; |
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250 * any additional values are equally spaced between these limits. |
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251 * (Forcing the upper and lower values to the limits ensures that |
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252 * dithering can't produce a color outside the selected gamut.) |
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253 */ |
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254 return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj); |
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255 } |
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256 |
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257 |
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258 LOCAL(int) |
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259 largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj) |
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260 /* Return largest input value that should map to j'th output value */ |
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261 /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */ |
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262 { |
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263 /* Breakpoints are halfway between values returned by output_value */ |
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264 return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj)); |
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265 } |
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266 |
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267 |
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268 /* |
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269 * Create the colormap. |
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270 */ |
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271 |
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272 LOCAL(void) |
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273 create_colormap (j_decompress_ptr cinfo) |
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274 { |
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275 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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276 JSAMPARRAY colormap; /* Created colormap */ |
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277 int total_colors; /* Number of distinct output colors */ |
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278 int i,j,k, nci, blksize, blkdist, ptr, val; |
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279 |
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280 /* Select number of colors for each component */ |
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281 total_colors = select_ncolors(cinfo, cquantize->Ncolors); |
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282 |
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283 /* Report selected color counts */ |
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284 if (cinfo->out_color_components == 3) |
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285 TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, |
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286 total_colors, cquantize->Ncolors[0], |
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287 cquantize->Ncolors[1], cquantize->Ncolors[2]); |
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288 else |
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289 TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors); |
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290 |
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291 /* Allocate and fill in the colormap. */ |
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292 /* The colors are ordered in the map in standard row-major order, */ |
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293 /* i.e. rightmost (highest-indexed) color changes most rapidly. */ |
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294 |
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295 colormap = (*cinfo->mem->alloc_sarray) |
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296 ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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297 (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components); |
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298 |
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299 /* blksize is number of adjacent repeated entries for a component */ |
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300 /* blkdist is distance between groups of identical entries for a component */ |
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301 blkdist = total_colors; |
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302 |
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303 for (i = 0; i < cinfo->out_color_components; i++) { |
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304 /* fill in colormap entries for i'th color component */ |
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305 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |
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306 blksize = blkdist / nci; |
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307 for (j = 0; j < nci; j++) { |
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308 /* Compute j'th output value (out of nci) for component */ |
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309 val = output_value(cinfo, i, j, nci-1); |
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310 /* Fill in all colormap entries that have this value of this component */ |
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311 for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) { |
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312 /* fill in blksize entries beginning at ptr */ |
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313 for (k = 0; k < blksize; k++) |
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314 colormap[i][ptr+k] = (JSAMPLE) val; |
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315 } |
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316 } |
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317 blkdist = blksize; /* blksize of this color is blkdist of next */ |
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318 } |
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319 |
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320 /* Save the colormap in private storage, |
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321 * where it will survive color quantization mode changes. |
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322 */ |
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323 cquantize->sv_colormap = colormap; |
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324 cquantize->sv_actual = total_colors; |
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325 } |
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326 |
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327 |
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328 /* |
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329 * Create the color index table. |
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330 */ |
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331 |
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332 LOCAL(void) |
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333 create_colorindex (j_decompress_ptr cinfo) |
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334 { |
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335 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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336 JSAMPROW indexptr; |
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337 int i,j,k, nci, blksize, val, pad; |
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338 |
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339 /* For ordered dither, we pad the color index tables by MAXJSAMPLE in |
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340 * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE). |
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341 * This is not necessary in the other dithering modes. However, we |
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342 * flag whether it was done in case user changes dithering mode. |
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343 */ |
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344 if (cinfo->dither_mode == JDITHER_ORDERED) { |
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345 pad = MAXJSAMPLE*2; |
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346 cquantize->is_padded = TRUE; |
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347 } else { |
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348 pad = 0; |
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349 cquantize->is_padded = FALSE; |
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350 } |
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351 |
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352 cquantize->colorindex = (*cinfo->mem->alloc_sarray) |
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353 ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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354 (JDIMENSION) (MAXJSAMPLE+1 + pad), |
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355 (JDIMENSION) cinfo->out_color_components); |
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356 |
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357 /* blksize is number of adjacent repeated entries for a component */ |
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358 blksize = cquantize->sv_actual; |
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359 |
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360 for (i = 0; i < cinfo->out_color_components; i++) { |
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361 /* fill in colorindex entries for i'th color component */ |
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362 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |
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363 blksize = blksize / nci; |
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364 |
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365 /* adjust colorindex pointers to provide padding at negative indexes. */ |
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366 if (pad) |
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367 cquantize->colorindex[i] += MAXJSAMPLE; |
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368 |
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369 /* in loop, val = index of current output value, */ |
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370 /* and k = largest j that maps to current val */ |
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371 indexptr = cquantize->colorindex[i]; |
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372 val = 0; |
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373 k = largest_input_value(cinfo, i, 0, nci-1); |
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374 for (j = 0; j <= MAXJSAMPLE; j++) { |
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375 while (j > k) /* advance val if past boundary */ |
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376 k = largest_input_value(cinfo, i, ++val, nci-1); |
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377 /* premultiply so that no multiplication needed in main processing */ |
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378 indexptr[j] = (JSAMPLE) (val * blksize); |
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379 } |
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380 /* Pad at both ends if necessary */ |
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381 if (pad) |
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382 for (j = 1; j <= MAXJSAMPLE; j++) { |
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383 indexptr[-j] = indexptr[0]; |
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384 indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE]; |
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385 } |
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386 } |
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387 } |
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388 |
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389 |
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390 /* |
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391 * Create an ordered-dither array for a component having ncolors |
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392 * distinct output values. |
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393 */ |
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394 |
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395 LOCAL(ODITHER_MATRIX_PTR) |
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396 make_odither_array (j_decompress_ptr cinfo, int ncolors) |
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397 { |
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398 ODITHER_MATRIX_PTR odither; |
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399 int j,k; |
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400 INT32 num,den; |
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401 |
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402 odither = (ODITHER_MATRIX_PTR) |
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403 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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404 SIZEOF(ODITHER_MATRIX)); |
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405 /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1). |
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406 * Hence the dither value for the matrix cell with fill order f |
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407 * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1). |
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408 * On 16-bit-int machine, be careful to avoid overflow. |
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409 */ |
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410 den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1)); |
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411 for (j = 0; j < ODITHER_SIZE; j++) { |
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412 for (k = 0; k < ODITHER_SIZE; k++) { |
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413 num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) |
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414 * MAXJSAMPLE; |
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415 /* Ensure round towards zero despite C's lack of consistency |
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416 * about rounding negative values in integer division... |
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417 */ |
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418 odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den); |
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419 } |
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420 } |
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421 return odither; |
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422 } |
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423 |
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424 |
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425 /* |
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426 * Create the ordered-dither tables. |
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427 * Components having the same number of representative colors may |
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428 * share a dither table. |
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429 */ |
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430 |
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431 LOCAL(void) |
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432 create_odither_tables (j_decompress_ptr cinfo) |
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433 { |
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434 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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435 ODITHER_MATRIX_PTR odither; |
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436 int i, j, nci; |
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437 |
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438 for (i = 0; i < cinfo->out_color_components; i++) { |
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439 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |
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440 odither = NULL; /* search for matching prior component */ |
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441 for (j = 0; j < i; j++) { |
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442 if (nci == cquantize->Ncolors[j]) { |
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443 odither = cquantize->odither[j]; |
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444 break; |
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445 } |
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446 } |
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447 if (odither == NULL) /* need a new table? */ |
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448 odither = make_odither_array(cinfo, nci); |
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449 cquantize->odither[i] = odither; |
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450 } |
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451 } |
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452 |
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453 |
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454 /* |
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455 * Map some rows of pixels to the output colormapped representation. |
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456 */ |
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457 |
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458 METHODDEF(void) |
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459 color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
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460 JSAMPARRAY output_buf, int num_rows) |
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461 /* General case, no dithering */ |
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462 { |
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463 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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464 JSAMPARRAY colorindex = cquantize->colorindex; |
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465 register int pixcode, ci; |
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466 register JSAMPROW ptrin, ptrout; |
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467 int row; |
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468 JDIMENSION col; |
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469 JDIMENSION width = cinfo->output_width; |
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470 register int nc = cinfo->out_color_components; |
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471 |
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472 for (row = 0; row < num_rows; row++) { |
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473 ptrin = input_buf[row]; |
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474 ptrout = output_buf[row]; |
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475 for (col = width; col > 0; col--) { |
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476 pixcode = 0; |
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477 for (ci = 0; ci < nc; ci++) { |
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478 pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); |
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479 } |
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480 *ptrout++ = (JSAMPLE) pixcode; |
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481 } |
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482 } |
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483 } |
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484 |
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485 |
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486 METHODDEF(void) |
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487 color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
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488 JSAMPARRAY output_buf, int num_rows) |
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489 /* Fast path for out_color_components==3, no dithering */ |
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490 { |
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491 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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492 register int pixcode; |
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493 register JSAMPROW ptrin, ptrout; |
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494 JSAMPROW colorindex0 = cquantize->colorindex[0]; |
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495 JSAMPROW colorindex1 = cquantize->colorindex[1]; |
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496 JSAMPROW colorindex2 = cquantize->colorindex[2]; |
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497 int row; |
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498 JDIMENSION col; |
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499 JDIMENSION width = cinfo->output_width; |
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500 |
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501 for (row = 0; row < num_rows; row++) { |
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502 ptrin = input_buf[row]; |
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503 ptrout = output_buf[row]; |
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504 for (col = width; col > 0; col--) { |
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505 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); |
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506 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); |
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507 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); |
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508 *ptrout++ = (JSAMPLE) pixcode; |
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509 } |
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510 } |
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511 } |
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512 |
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513 |
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514 METHODDEF(void) |
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515 quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
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516 JSAMPARRAY output_buf, int num_rows) |
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517 /* General case, with ordered dithering */ |
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518 { |
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519 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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520 register JSAMPROW input_ptr; |
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521 register JSAMPROW output_ptr; |
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522 JSAMPROW colorindex_ci; |
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523 int * dither; /* points to active row of dither matrix */ |
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524 int row_index, col_index; /* current indexes into dither matrix */ |
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525 int nc = cinfo->out_color_components; |
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526 int ci; |
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527 int row; |
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528 JDIMENSION col; |
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529 JDIMENSION width = cinfo->output_width; |
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530 |
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531 for (row = 0; row < num_rows; row++) { |
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532 /* Initialize output values to 0 so can process components separately */ |
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533 jzero_far((void FAR *) output_buf[row], |
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534 (size_t) (width * SIZEOF(JSAMPLE))); |
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535 row_index = cquantize->row_index; |
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536 for (ci = 0; ci < nc; ci++) { |
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537 input_ptr = input_buf[row] + ci; |
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538 output_ptr = output_buf[row]; |
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539 colorindex_ci = cquantize->colorindex[ci]; |
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540 dither = cquantize->odither[ci][row_index]; |
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541 col_index = 0; |
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542 |
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543 for (col = width; col > 0; col--) { |
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544 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, |
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545 * select output value, accumulate into output code for this pixel. |
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546 * Range-limiting need not be done explicitly, as we have extended |
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547 * the colorindex table to produce the right answers for out-of-range |
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548 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the |
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549 * required amount of padding. |
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550 */ |
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551 *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; |
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552 input_ptr += nc; |
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553 output_ptr++; |
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554 col_index = (col_index + 1) & ODITHER_MASK; |
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555 } |
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556 } |
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557 /* Advance row index for next row */ |
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558 row_index = (row_index + 1) & ODITHER_MASK; |
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559 cquantize->row_index = row_index; |
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560 } |
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561 } |
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562 |
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563 |
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564 METHODDEF(void) |
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565 quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
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566 JSAMPARRAY output_buf, int num_rows) |
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567 /* Fast path for out_color_components==3, with ordered dithering */ |
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568 { |
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569 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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570 register int pixcode; |
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571 register JSAMPROW input_ptr; |
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572 register JSAMPROW output_ptr; |
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573 JSAMPROW colorindex0 = cquantize->colorindex[0]; |
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574 JSAMPROW colorindex1 = cquantize->colorindex[1]; |
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575 JSAMPROW colorindex2 = cquantize->colorindex[2]; |
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576 int * dither0; /* points to active row of dither matrix */ |
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577 int * dither1; |
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578 int * dither2; |
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579 int row_index, col_index; /* current indexes into dither matrix */ |
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580 int row; |
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581 JDIMENSION col; |
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582 JDIMENSION width = cinfo->output_width; |
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583 |
|
584 for (row = 0; row < num_rows; row++) { |
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585 row_index = cquantize->row_index; |
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586 input_ptr = input_buf[row]; |
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587 output_ptr = output_buf[row]; |
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588 dither0 = cquantize->odither[0][row_index]; |
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589 dither1 = cquantize->odither[1][row_index]; |
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590 dither2 = cquantize->odither[2][row_index]; |
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591 col_index = 0; |
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592 |
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593 for (col = width; col > 0; col--) { |
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594 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + |
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595 dither0[col_index]]); |
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596 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + |
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597 dither1[col_index]]); |
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598 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + |
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599 dither2[col_index]]); |
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600 *output_ptr++ = (JSAMPLE) pixcode; |
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601 col_index = (col_index + 1) & ODITHER_MASK; |
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602 } |
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603 row_index = (row_index + 1) & ODITHER_MASK; |
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604 cquantize->row_index = row_index; |
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605 } |
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606 } |
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607 |
|
608 |
|
609 METHODDEF(void) |
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610 quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
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611 JSAMPARRAY output_buf, int num_rows) |
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612 /* General case, with Floyd-Steinberg dithering */ |
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613 { |
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614 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
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615 register LOCFSERROR cur; /* current error or pixel value */ |
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616 LOCFSERROR belowerr; /* error for pixel below cur */ |
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617 LOCFSERROR bpreverr; /* error for below/prev col */ |
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618 LOCFSERROR bnexterr; /* error for below/next col */ |
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619 LOCFSERROR delta; |
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620 register FSERRPTR errorptr; /* => fserrors[] at column before current */ |
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621 register JSAMPROW input_ptr; |
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622 register JSAMPROW output_ptr; |
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623 JSAMPROW colorindex_ci; |
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624 JSAMPROW colormap_ci; |
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625 int pixcode; |
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626 int nc = cinfo->out_color_components; |
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627 int dir; /* 1 for left-to-right, -1 for right-to-left */ |
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628 int dirnc; /* dir * nc */ |
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629 int ci; |
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630 int row; |
|
631 JDIMENSION col; |
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632 JDIMENSION width = cinfo->output_width; |
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633 JSAMPLE *range_limit = cinfo->sample_range_limit; |
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634 SHIFT_TEMPS |
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635 |
|
636 for (row = 0; row < num_rows; row++) { |
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637 /* Initialize output values to 0 so can process components separately */ |
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638 jzero_far((void FAR *) output_buf[row], |
|
639 (size_t) (width * SIZEOF(JSAMPLE))); |
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640 for (ci = 0; ci < nc; ci++) { |
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641 input_ptr = input_buf[row] + ci; |
|
642 output_ptr = output_buf[row]; |
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643 if (cquantize->on_odd_row) { |
|
644 /* work right to left in this row */ |
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645 input_ptr += (width-1) * nc; /* so point to rightmost pixel */ |
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646 output_ptr += width-1; |
|
647 dir = -1; |
|
648 dirnc = -nc; |
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649 errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */ |
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650 } else { |
|
651 /* work left to right in this row */ |
|
652 dir = 1; |
|
653 dirnc = nc; |
|
654 errorptr = cquantize->fserrors[ci]; /* => entry before first column */ |
|
655 } |
|
656 colorindex_ci = cquantize->colorindex[ci]; |
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657 colormap_ci = cquantize->sv_colormap[ci]; |
|
658 /* Preset error values: no error propagated to first pixel from left */ |
|
659 cur = 0; |
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660 /* and no error propagated to row below yet */ |
|
661 belowerr = bpreverr = 0; |
|
662 |
|
663 for (col = width; col > 0; col--) { |
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664 /* cur holds the error propagated from the previous pixel on the |
|
665 * current line. Add the error propagated from the previous line |
|
666 * to form the complete error correction term for this pixel, and |
|
667 * round the error term (which is expressed * 16) to an integer. |
|
668 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct |
|
669 * for either sign of the error value. |
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670 * Note: errorptr points to *previous* column's array entry. |
|
671 */ |
|
672 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4); |
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673 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE. |
|
674 * The maximum error is +- MAXJSAMPLE; this sets the required size |
|
675 * of the range_limit array. |
|
676 */ |
|
677 cur += GETJSAMPLE(*input_ptr); |
|
678 cur = GETJSAMPLE(range_limit[cur]); |
|
679 /* Select output value, accumulate into output code for this pixel */ |
|
680 pixcode = GETJSAMPLE(colorindex_ci[cur]); |
|
681 *output_ptr += (JSAMPLE) pixcode; |
|
682 /* Compute actual representation error at this pixel */ |
|
683 /* Note: we can do this even though we don't have the final */ |
|
684 /* pixel code, because the colormap is orthogonal. */ |
|
685 cur -= GETJSAMPLE(colormap_ci[pixcode]); |
|
686 /* Compute error fractions to be propagated to adjacent pixels. |
|
687 * Add these into the running sums, and simultaneously shift the |
|
688 * next-line error sums left by 1 column. |
|
689 */ |
|
690 bnexterr = cur; |
|
691 delta = cur * 2; |
|
692 cur += delta; /* form error * 3 */ |
|
693 errorptr[0] = (FSERROR) (bpreverr + cur); |
|
694 cur += delta; /* form error * 5 */ |
|
695 bpreverr = belowerr + cur; |
|
696 belowerr = bnexterr; |
|
697 cur += delta; /* form error * 7 */ |
|
698 /* At this point cur contains the 7/16 error value to be propagated |
|
699 * to the next pixel on the current line, and all the errors for the |
|
700 * next line have been shifted over. We are therefore ready to move on. |
|
701 */ |
|
702 input_ptr += dirnc; /* advance input ptr to next column */ |
|
703 output_ptr += dir; /* advance output ptr to next column */ |
|
704 errorptr += dir; /* advance errorptr to current column */ |
|
705 } |
|
706 /* Post-loop cleanup: we must unload the final error value into the |
|
707 * final fserrors[] entry. Note we need not unload belowerr because |
|
708 * it is for the dummy column before or after the actual array. |
|
709 */ |
|
710 errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */ |
|
711 } |
|
712 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE); |
|
713 } |
|
714 } |
|
715 |
|
716 |
|
717 /* |
|
718 * Allocate workspace for Floyd-Steinberg errors. |
|
719 */ |
|
720 |
|
721 LOCAL(void) |
|
722 alloc_fs_workspace (j_decompress_ptr cinfo) |
|
723 { |
|
724 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
|
725 size_t arraysize; |
|
726 int i; |
|
727 |
|
728 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); |
|
729 for (i = 0; i < cinfo->out_color_components; i++) { |
|
730 cquantize->fserrors[i] = (FSERRPTR) |
|
731 (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize); |
|
732 } |
|
733 } |
|
734 |
|
735 |
|
736 /* |
|
737 * Initialize for one-pass color quantization. |
|
738 */ |
|
739 |
|
740 METHODDEF(void) |
|
741 start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan) |
|
742 { |
|
743 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |
|
744 size_t arraysize; |
|
745 int i; |
|
746 |
|
747 /* Install my colormap. */ |
|
748 cinfo->colormap = cquantize->sv_colormap; |
|
749 cinfo->actual_number_of_colors = cquantize->sv_actual; |
|
750 |
|
751 /* Initialize for desired dithering mode. */ |
|
752 switch (cinfo->dither_mode) { |
|
753 case JDITHER_NONE: |
|
754 if (cinfo->out_color_components == 3) |
|
755 cquantize->pub.color_quantize = color_quantize3; |
|
756 else |
|
757 cquantize->pub.color_quantize = color_quantize; |
|
758 break; |
|
759 case JDITHER_ORDERED: |
|
760 if (cinfo->out_color_components == 3) |
|
761 cquantize->pub.color_quantize = quantize3_ord_dither; |
|
762 else |
|
763 cquantize->pub.color_quantize = quantize_ord_dither; |
|
764 cquantize->row_index = 0; /* initialize state for ordered dither */ |
|
765 /* If user changed to ordered dither from another mode, |
|
766 * we must recreate the color index table with padding. |
|
767 * This will cost extra space, but probably isn't very likely. |
|
768 */ |
|
769 if (! cquantize->is_padded) |
|
770 create_colorindex(cinfo); |
|
771 /* Create ordered-dither tables if we didn't already. */ |
|
772 if (cquantize->odither[0] == NULL) |
|
773 create_odither_tables(cinfo); |
|
774 break; |
|
775 case JDITHER_FS: |
|
776 cquantize->pub.color_quantize = quantize_fs_dither; |
|
777 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */ |
|
778 /* Allocate Floyd-Steinberg workspace if didn't already. */ |
|
779 if (cquantize->fserrors[0] == NULL) |
|
780 alloc_fs_workspace(cinfo); |
|
781 /* Initialize the propagated errors to zero. */ |
|
782 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); |
|
783 for (i = 0; i < cinfo->out_color_components; i++) |
|
784 jzero_far((void FAR *) cquantize->fserrors[i], arraysize); |
|
785 break; |
|
786 default: |
|
787 ERREXIT(cinfo, JERR_NOT_COMPILED); |
|
788 break; |
|
789 } |
|
790 } |
|
791 |
|
792 |
|
793 /* |
|
794 * Finish up at the end of the pass. |
|
795 */ |
|
796 |
|
797 METHODDEF(void) |
|
798 finish_pass_1_quant (j_decompress_ptr cinfo) |
|
799 { |
|
800 /* no work in 1-pass case */ |
|
801 } |
|
802 |
|
803 |
|
804 /* |
|
805 * Switch to a new external colormap between output passes. |
|
806 * Shouldn't get to this module! |
|
807 */ |
|
808 |
|
809 METHODDEF(void) |
|
810 new_color_map_1_quant (j_decompress_ptr cinfo) |
|
811 { |
|
812 ERREXIT(cinfo, JERR_MODE_CHANGE); |
|
813 } |
|
814 |
|
815 |
|
816 /* |
|
817 * Module initialization routine for 1-pass color quantization. |
|
818 */ |
|
819 |
|
820 GLOBAL(void) |
|
821 jinit_1pass_quantizer (j_decompress_ptr cinfo) |
|
822 { |
|
823 my_cquantize_ptr cquantize; |
|
824 |
|
825 cquantize = (my_cquantize_ptr) |
|
826 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
|
827 SIZEOF(my_cquantizer)); |
|
828 cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize; |
|
829 cquantize->pub.start_pass = start_pass_1_quant; |
|
830 cquantize->pub.finish_pass = finish_pass_1_quant; |
|
831 cquantize->pub.new_color_map = new_color_map_1_quant; |
|
832 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */ |
|
833 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */ |
|
834 |
|
835 /* Make sure my internal arrays won't overflow */ |
|
836 if (cinfo->out_color_components > MAX_Q_COMPS) |
|
837 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS); |
|
838 /* Make sure colormap indexes can be represented by JSAMPLEs */ |
|
839 if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1)) |
|
840 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1); |
|
841 |
|
842 /* Create the colormap and color index table. */ |
|
843 create_colormap(cinfo); |
|
844 create_colorindex(cinfo); |
|
845 |
|
846 /* Allocate Floyd-Steinberg workspace now if requested. |
|
847 * We do this now since it is FAR storage and may affect the memory |
|
848 * manager's space calculations. If the user changes to FS dither |
|
849 * mode in a later pass, we will allocate the space then, and will |
|
850 * possibly overrun the max_memory_to_use setting. |
|
851 */ |
|
852 if (cinfo->dither_mode == JDITHER_FS) |
|
853 alloc_fs_workspace(cinfo); |
|
854 } |
|
855 |
|
856 #endif /* QUANT_1PASS_SUPPORTED */ |