1 | /* |
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2 | * jdmerge.c |
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3 | * |
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4 | * Copyright (C) 1994-1996, 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 code for merged upsampling/color conversion. |
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9 | * |
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10 | * This file combines functions from jdsample.c and jdcolor.c; |
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11 | * read those files first to understand what's going on. |
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12 | * |
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13 | * When the chroma components are to be upsampled by simple replication |
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14 | * (ie, box filtering), we can save some work in color conversion by |
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15 | * calculating all the output pixels corresponding to a pair of chroma |
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16 | * samples at one time. In the conversion equations |
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17 | * R = Y + K1 * Cr |
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18 | * G = Y + K2 * Cb + K3 * Cr |
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19 | * B = Y + K4 * Cb |
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20 | * only the Y term varies among the group of pixels corresponding to a pair |
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21 | * of chroma samples, so the rest of the terms can be calculated just once. |
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22 | * At typical sampling ratios, this eliminates half or three-quarters of the |
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23 | * multiplications needed for color conversion. |
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24 | * |
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25 | * This file currently provides implementations for the following cases: |
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26 | * YCbCr => RGB color conversion only. |
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27 | * Sampling ratios of 2h1v or 2h2v. |
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28 | * No scaling needed at upsample time. |
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29 | * Corner-aligned (non-CCIR601) sampling alignment. |
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30 | * Other special cases could be added, but in most applications these are |
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31 | * the only common cases. (For uncommon cases we fall back on the more |
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32 | * general code in jdsample.c and jdcolor.c.) |
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33 | */ |
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34 | |
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35 | #define JPEG_INTERNALS |
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36 | #include "jinclude.h" |
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37 | #include "jpeglib.h" |
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38 | |
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39 | #ifdef UPSAMPLE_MERGING_SUPPORTED |
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40 | |
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41 | |
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42 | /* Private subobject */ |
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43 | |
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44 | typedef struct { |
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45 | struct jpeg_upsampler pub; /* public fields */ |
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46 | |
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47 | /* Pointer to routine to do actual upsampling/conversion of one row group */ |
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48 | JMETHOD(void, upmethod, (j_decompress_ptr cinfo, |
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49 | JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, |
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50 | JSAMPARRAY output_buf)); |
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51 | |
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52 | /* Private state for YCC->RGB conversion */ |
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53 | int * Cr_r_tab; /* => table for Cr to R conversion */ |
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54 | int * Cb_b_tab; /* => table for Cb to B conversion */ |
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55 | INT32 * Cr_g_tab; /* => table for Cr to G conversion */ |
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56 | INT32 * Cb_g_tab; /* => table for Cb to G conversion */ |
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57 | |
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58 | /* For 2:1 vertical sampling, we produce two output rows at a time. |
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59 | * We need a "spare" row buffer to hold the second output row if the |
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60 | * application provides just a one-row buffer; we also use the spare |
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61 | * to discard the dummy last row if the image height is odd. |
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62 | */ |
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63 | JSAMPROW spare_row; |
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64 | boolean spare_full; /* T if spare buffer is occupied */ |
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65 | |
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66 | JDIMENSION out_row_width; /* samples per output row */ |
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67 | JDIMENSION rows_to_go; /* counts rows remaining in image */ |
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68 | } my_upsampler; |
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69 | |
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70 | typedef my_upsampler * my_upsample_ptr; |
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71 | |
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72 | #define SCALEBITS 16 /* speediest right-shift on some machines */ |
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73 | #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) |
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74 | #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) |
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75 | |
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76 | |
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77 | /* |
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78 | * Initialize tables for YCC->RGB colorspace conversion. |
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79 | * This is taken directly from jdcolor.c; see that file for more info. |
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80 | */ |
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81 | |
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82 | LOCAL(void) |
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83 | build_ycc_rgb_table (j_decompress_ptr cinfo) |
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84 | { |
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85 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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86 | int i; |
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87 | INT32 x; |
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88 | SHIFT_TEMPS |
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89 | |
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90 | upsample->Cr_r_tab = (int *) |
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91 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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92 | (MAXJSAMPLE+1) * SIZEOF(int)); |
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93 | upsample->Cb_b_tab = (int *) |
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94 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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95 | (MAXJSAMPLE+1) * SIZEOF(int)); |
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96 | upsample->Cr_g_tab = (INT32 *) |
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97 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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98 | (MAXJSAMPLE+1) * SIZEOF(INT32)); |
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99 | upsample->Cb_g_tab = (INT32 *) |
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100 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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101 | (MAXJSAMPLE+1) * SIZEOF(INT32)); |
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102 | |
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103 | for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) { |
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104 | /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */ |
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105 | /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */ |
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106 | /* Cr=>R value is nearest int to 1.40200 * x */ |
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107 | upsample->Cr_r_tab[i] = (int) |
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108 | RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); |
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109 | /* Cb=>B value is nearest int to 1.77200 * x */ |
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110 | upsample->Cb_b_tab[i] = (int) |
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111 | RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); |
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112 | /* Cr=>G value is scaled-up -0.71414 * x */ |
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113 | upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x; |
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114 | /* Cb=>G value is scaled-up -0.34414 * x */ |
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115 | /* We also add in ONE_HALF so that need not do it in inner loop */ |
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116 | upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; |
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117 | } |
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118 | } |
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119 | |
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120 | |
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121 | /* |
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122 | * Initialize for an upsampling pass. |
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123 | */ |
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124 | |
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125 | METHODDEF(void) |
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126 | start_pass_merged_upsample (j_decompress_ptr cinfo) |
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127 | { |
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128 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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129 | |
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130 | /* Mark the spare buffer empty */ |
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131 | upsample->spare_full = FALSE; |
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132 | /* Initialize total-height counter for detecting bottom of image */ |
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133 | upsample->rows_to_go = cinfo->output_height; |
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134 | } |
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135 | |
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136 | |
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137 | /* |
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138 | * Control routine to do upsampling (and color conversion). |
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139 | * |
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140 | * The control routine just handles the row buffering considerations. |
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141 | */ |
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142 | |
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143 | METHODDEF(void) |
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144 | merged_2v_upsample (j_decompress_ptr cinfo, |
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145 | JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, |
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146 | JDIMENSION in_row_groups_avail, |
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147 | JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
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148 | JDIMENSION out_rows_avail) |
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149 | /* 2:1 vertical sampling case: may need a spare row. */ |
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150 | { |
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151 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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152 | JSAMPROW work_ptrs[2]; |
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153 | JDIMENSION num_rows; /* number of rows returned to caller */ |
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154 | |
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155 | if (upsample->spare_full) { |
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156 | /* If we have a spare row saved from a previous cycle, just return it. */ |
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157 | jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0, |
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158 | 1, upsample->out_row_width); |
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159 | num_rows = 1; |
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160 | upsample->spare_full = FALSE; |
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161 | } else { |
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162 | /* Figure number of rows to return to caller. */ |
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163 | num_rows = 2; |
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164 | /* Not more than the distance to the end of the image. */ |
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165 | if (num_rows > upsample->rows_to_go) |
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166 | num_rows = upsample->rows_to_go; |
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167 | /* And not more than what the client can accept: */ |
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168 | out_rows_avail -= *out_row_ctr; |
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169 | if (num_rows > out_rows_avail) |
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170 | num_rows = out_rows_avail; |
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171 | /* Create output pointer array for upsampler. */ |
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172 | work_ptrs[0] = output_buf[*out_row_ctr]; |
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173 | if (num_rows > 1) { |
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174 | work_ptrs[1] = output_buf[*out_row_ctr + 1]; |
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175 | } else { |
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176 | work_ptrs[1] = upsample->spare_row; |
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177 | upsample->spare_full = TRUE; |
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178 | } |
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179 | /* Now do the upsampling. */ |
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180 | (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs); |
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181 | } |
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182 | |
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183 | /* Adjust counts */ |
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184 | *out_row_ctr += num_rows; |
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185 | upsample->rows_to_go -= num_rows; |
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186 | /* When the buffer is emptied, declare this input row group consumed */ |
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187 | if (! upsample->spare_full) |
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188 | (*in_row_group_ctr)++; |
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189 | } |
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190 | |
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191 | |
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192 | METHODDEF(void) |
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193 | merged_1v_upsample (j_decompress_ptr cinfo, |
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194 | JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, |
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195 | JDIMENSION in_row_groups_avail, |
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196 | JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
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197 | JDIMENSION out_rows_avail) |
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198 | /* 1:1 vertical sampling case: much easier, never need a spare row. */ |
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199 | { |
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200 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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201 | |
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202 | /* Just do the upsampling. */ |
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203 | (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, |
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204 | output_buf + *out_row_ctr); |
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205 | /* Adjust counts */ |
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206 | (*out_row_ctr)++; |
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207 | (*in_row_group_ctr)++; |
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208 | } |
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209 | |
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210 | |
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211 | /* |
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212 | * These are the routines invoked by the control routines to do |
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213 | * the actual upsampling/conversion. One row group is processed per call. |
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214 | * |
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215 | * Note: since we may be writing directly into application-supplied buffers, |
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216 | * we have to be honest about the output width; we can't assume the buffer |
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217 | * has been rounded up to an even width. |
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218 | */ |
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219 | |
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220 | |
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221 | /* |
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222 | * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical. |
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223 | */ |
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224 | |
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225 | METHODDEF(void) |
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226 | h2v1_merged_upsample (j_decompress_ptr cinfo, |
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227 | JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, |
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228 | JSAMPARRAY output_buf) |
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229 | { |
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230 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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231 | register int y, cred, cgreen, cblue; |
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232 | int cb, cr; |
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233 | register JSAMPROW outptr; |
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234 | JSAMPROW inptr0, inptr1, inptr2; |
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235 | JDIMENSION col; |
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236 | /* copy these pointers into registers if possible */ |
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237 | register JSAMPLE * range_limit = cinfo->sample_range_limit; |
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238 | int * Crrtab = upsample->Cr_r_tab; |
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239 | int * Cbbtab = upsample->Cb_b_tab; |
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240 | INT32 * Crgtab = upsample->Cr_g_tab; |
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241 | INT32 * Cbgtab = upsample->Cb_g_tab; |
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242 | SHIFT_TEMPS |
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243 | |
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244 | inptr0 = input_buf[0][in_row_group_ctr]; |
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245 | inptr1 = input_buf[1][in_row_group_ctr]; |
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246 | inptr2 = input_buf[2][in_row_group_ctr]; |
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247 | outptr = output_buf[0]; |
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248 | /* Loop for each pair of output pixels */ |
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249 | for (col = cinfo->output_width >> 1; col > 0; col--) { |
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250 | /* Do the chroma part of the calculation */ |
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251 | cb = GETJSAMPLE(*inptr1++); |
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252 | cr = GETJSAMPLE(*inptr2++); |
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253 | cred = Crrtab[cr]; |
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254 | cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); |
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255 | cblue = Cbbtab[cb]; |
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256 | /* Fetch 2 Y values and emit 2 pixels */ |
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257 | y = GETJSAMPLE(*inptr0++); |
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258 | outptr[RGB_RED] = range_limit[y + cred]; |
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259 | outptr[RGB_GREEN] = range_limit[y + cgreen]; |
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260 | outptr[RGB_BLUE] = range_limit[y + cblue]; |
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261 | outptr += RGB_PIXELSIZE; |
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262 | y = GETJSAMPLE(*inptr0++); |
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263 | outptr[RGB_RED] = range_limit[y + cred]; |
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264 | outptr[RGB_GREEN] = range_limit[y + cgreen]; |
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265 | outptr[RGB_BLUE] = range_limit[y + cblue]; |
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266 | outptr += RGB_PIXELSIZE; |
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267 | } |
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268 | /* If image width is odd, do the last output column separately */ |
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269 | if (cinfo->output_width & 1) { |
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270 | cb = GETJSAMPLE(*inptr1); |
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271 | cr = GETJSAMPLE(*inptr2); |
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272 | cred = Crrtab[cr]; |
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273 | cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); |
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274 | cblue = Cbbtab[cb]; |
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275 | y = GETJSAMPLE(*inptr0); |
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276 | outptr[RGB_RED] = range_limit[y + cred]; |
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277 | outptr[RGB_GREEN] = range_limit[y + cgreen]; |
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278 | outptr[RGB_BLUE] = range_limit[y + cblue]; |
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279 | } |
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280 | } |
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281 | |
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282 | |
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283 | /* |
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284 | * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical. |
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285 | */ |
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286 | |
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287 | METHODDEF(void) |
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288 | h2v2_merged_upsample (j_decompress_ptr cinfo, |
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289 | JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, |
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290 | JSAMPARRAY output_buf) |
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291 | { |
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292 | my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; |
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293 | register int y, cred, cgreen, cblue; |
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294 | int cb, cr; |
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295 | register JSAMPROW outptr0, outptr1; |
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296 | JSAMPROW inptr00, inptr01, inptr1, inptr2; |
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297 | JDIMENSION col; |
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298 | /* copy these pointers into registers if possible */ |
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299 | register JSAMPLE * range_limit = cinfo->sample_range_limit; |
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300 | int * Crrtab = upsample->Cr_r_tab; |
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301 | int * Cbbtab = upsample->Cb_b_tab; |
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302 | INT32 * Crgtab = upsample->Cr_g_tab; |
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303 | INT32 * Cbgtab = upsample->Cb_g_tab; |
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304 | SHIFT_TEMPS |
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305 | |
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306 | inptr00 = input_buf[0][in_row_group_ctr*2]; |
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307 | inptr01 = input_buf[0][in_row_group_ctr*2 + 1]; |
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308 | inptr1 = input_buf[1][in_row_group_ctr]; |
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309 | inptr2 = input_buf[2][in_row_group_ctr]; |
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310 | outptr0 = output_buf[0]; |
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311 | outptr1 = output_buf[1]; |
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312 | /* Loop for each group of output pixels */ |
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313 | for (col = cinfo->output_width >> 1; col > 0; col--) { |
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314 | /* Do the chroma part of the calculation */ |
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315 | cb = GETJSAMPLE(*inptr1++); |
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316 | cr = GETJSAMPLE(*inptr2++); |
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317 | cred = Crrtab[cr]; |
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318 | cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); |
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319 | cblue = Cbbtab[cb]; |
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320 | /* Fetch 4 Y values and emit 4 pixels */ |
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321 | y = GETJSAMPLE(*inptr00++); |
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322 | outptr0[RGB_RED] = range_limit[y + cred]; |
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323 | outptr0[RGB_GREEN] = range_limit[y + cgreen]; |
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324 | outptr0[RGB_BLUE] = range_limit[y + cblue]; |
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325 | outptr0 += RGB_PIXELSIZE; |
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326 | y = GETJSAMPLE(*inptr00++); |
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327 | outptr0[RGB_RED] = range_limit[y + cred]; |
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328 | outptr0[RGB_GREEN] = range_limit[y + cgreen]; |
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329 | outptr0[RGB_BLUE] = range_limit[y + cblue]; |
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330 | outptr0 += RGB_PIXELSIZE; |
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331 | y = GETJSAMPLE(*inptr01++); |
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332 | outptr1[RGB_RED] = range_limit[y + cred]; |
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333 | outptr1[RGB_GREEN] = range_limit[y + cgreen]; |
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334 | outptr1[RGB_BLUE] = range_limit[y + cblue]; |
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335 | outptr1 += RGB_PIXELSIZE; |
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336 | y = GETJSAMPLE(*inptr01++); |
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337 | outptr1[RGB_RED] = range_limit[y + cred]; |
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338 | outptr1[RGB_GREEN] = range_limit[y + cgreen]; |
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339 | outptr1[RGB_BLUE] = range_limit[y + cblue]; |
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340 | outptr1 += RGB_PIXELSIZE; |
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341 | } |
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342 | /* If image width is odd, do the last output column separately */ |
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343 | if (cinfo->output_width & 1) { |
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344 | cb = GETJSAMPLE(*inptr1); |
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345 | cr = GETJSAMPLE(*inptr2); |
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346 | cred = Crrtab[cr]; |
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347 | cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); |
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348 | cblue = Cbbtab[cb]; |
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349 | y = GETJSAMPLE(*inptr00); |
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350 | outptr0[RGB_RED] = range_limit[y + cred]; |
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351 | outptr0[RGB_GREEN] = range_limit[y + cgreen]; |
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352 | outptr0[RGB_BLUE] = range_limit[y + cblue]; |
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353 | y = GETJSAMPLE(*inptr01); |
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354 | outptr1[RGB_RED] = range_limit[y + cred]; |
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355 | outptr1[RGB_GREEN] = range_limit[y + cgreen]; |
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356 | outptr1[RGB_BLUE] = range_limit[y + cblue]; |
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357 | } |
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358 | } |
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359 | |
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360 | |
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361 | /* |
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362 | * Module initialization routine for merged upsampling/color conversion. |
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363 | * |
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364 | * NB: this is called under the conditions determined by use_merged_upsample() |
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365 | * in jdmaster.c. That routine MUST correspond to the actual capabilities |
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366 | * of this module; no safety checks are made here. |
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367 | */ |
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368 | |
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369 | GLOBAL(void) |
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370 | jinit_merged_upsampler (j_decompress_ptr cinfo) |
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371 | { |
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372 | my_upsample_ptr upsample; |
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373 | |
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374 | upsample = (my_upsample_ptr) |
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375 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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376 | SIZEOF(my_upsampler)); |
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377 | cinfo->upsample = (struct jpeg_upsampler *) upsample; |
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378 | upsample->pub.start_pass = start_pass_merged_upsample; |
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379 | upsample->pub.need_context_rows = FALSE; |
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380 | |
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381 | upsample->out_row_width = cinfo->output_width * cinfo->out_color_components; |
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382 | |
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383 | if (cinfo->max_v_samp_factor == 2) { |
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384 | upsample->pub.upsample = merged_2v_upsample; |
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385 | upsample->upmethod = h2v2_merged_upsample; |
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386 | /* Allocate a spare row buffer */ |
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387 | upsample->spare_row = (JSAMPROW) |
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388 | (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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389 | (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE))); |
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390 | } else { |
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391 | upsample->pub.upsample = merged_1v_upsample; |
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392 | upsample->upmethod = h2v1_merged_upsample; |
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393 | /* No spare row needed */ |
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394 | upsample->spare_row = NULL; |
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395 | } |
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396 | |
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397 | build_ycc_rgb_table(cinfo); |
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398 | } |
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399 | |
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400 | #endif /* UPSAMPLE_MERGING_SUPPORTED */ |
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