4 * Copyright (C) 1991-1997, Thomas G. Lane.
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5 * Modified 2002-2009 by Guido Vollbeding.
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6 * This file is part of the Independent JPEG Group's software.
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7 * For conditions of distribution and use, see the accompanying README file.
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9 * This file contains master control logic for the JPEG decompressor.
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10 * These routines are concerned with selecting the modules to be executed
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11 * and with determining the number of passes and the work to be done in each
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15 #define JPEG_INTERNALS
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16 #include "jinclude.h"
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17 #include "jpeglib.h"
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23 struct jpeg_decomp_master pub; /* public fields */
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25 int pass_number; /* # of passes completed */
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27 boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
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29 /* Saved references to initialized quantizer modules,
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30 * in case we need to switch modes.
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32 struct jpeg_color_quantizer * quantizer_1pass;
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33 struct jpeg_color_quantizer * quantizer_2pass;
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36 typedef my_decomp_master * my_master_ptr;
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40 * Determine whether merged upsample/color conversion should be used.
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41 * CRUCIAL: this must match the actual capabilities of jdmerge.c!
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45 use_merged_upsample (j_decompress_ptr cinfo)
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47 #ifdef UPSAMPLE_MERGING_SUPPORTED
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48 /* Merging is the equivalent of plain box-filter upsampling */
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49 if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
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51 /* jdmerge.c only supports YCC=>RGB color conversion */
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52 if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
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53 cinfo->out_color_space != JCS_RGB ||
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54 cinfo->out_color_components != RGB_PIXELSIZE)
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56 /* and it only handles 2h1v or 2h2v sampling ratios */
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57 if (cinfo->comp_info[0].h_samp_factor != 2 ||
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58 cinfo->comp_info[1].h_samp_factor != 1 ||
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59 cinfo->comp_info[2].h_samp_factor != 1 ||
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60 cinfo->comp_info[0].v_samp_factor > 2 ||
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61 cinfo->comp_info[1].v_samp_factor != 1 ||
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62 cinfo->comp_info[2].v_samp_factor != 1)
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64 /* furthermore, it doesn't work if we've scaled the IDCTs differently */
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65 if (cinfo->comp_info[0].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
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66 cinfo->comp_info[1].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
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67 cinfo->comp_info[2].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
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68 cinfo->comp_info[0].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
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69 cinfo->comp_info[1].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
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70 cinfo->comp_info[2].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size)
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72 /* ??? also need to test for upsample-time rescaling, when & if supported */
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73 return TRUE; /* by golly, it'll work... */
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81 * Compute output image dimensions and related values.
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82 * NOTE: this is exported for possible use by application.
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83 * Hence it mustn't do anything that can't be done twice.
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84 * Also note that it may be called before the master module is initialized!
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88 jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
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89 /* Do computations that are needed before master selection phase.
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90 * This function is used for full decompression.
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93 #ifdef IDCT_SCALING_SUPPORTED
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95 jpeg_component_info *compptr;
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98 /* Prevent application from calling me at wrong times */
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99 if (cinfo->global_state != DSTATE_READY)
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100 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
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102 /* Compute core output image dimensions and DCT scaling choices. */
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103 jpeg_core_output_dimensions(cinfo);
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105 #ifdef IDCT_SCALING_SUPPORTED
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107 /* In selecting the actual DCT scaling for each component, we try to
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108 * scale up the chroma components via IDCT scaling rather than upsampling.
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109 * This saves time if the upsampler gets to use 1:1 scaling.
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110 * Note this code adapts subsampling ratios which are powers of 2.
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112 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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115 while (cinfo->min_DCT_h_scaled_size * ssize <=
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116 (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
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117 (cinfo->max_h_samp_factor % (compptr->h_samp_factor * ssize * 2)) == 0) {
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120 compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size * ssize;
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122 while (cinfo->min_DCT_v_scaled_size * ssize <=
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123 (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
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124 (cinfo->max_v_samp_factor % (compptr->v_samp_factor * ssize * 2)) == 0) {
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127 compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size * ssize;
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129 /* We don't support IDCT ratios larger than 2. */
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130 if (compptr->DCT_h_scaled_size > compptr->DCT_v_scaled_size * 2)
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131 compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size * 2;
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132 else if (compptr->DCT_v_scaled_size > compptr->DCT_h_scaled_size * 2)
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133 compptr->DCT_v_scaled_size = compptr->DCT_h_scaled_size * 2;
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136 /* Recompute downsampled dimensions of components;
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137 * application needs to know these if using raw downsampled data.
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139 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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141 /* Size in samples, after IDCT scaling */
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142 compptr->downsampled_width = (JDIMENSION)
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143 jdiv_round_up((long) cinfo->image_width *
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144 (long) (compptr->h_samp_factor * compptr->DCT_h_scaled_size),
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145 (long) (cinfo->max_h_samp_factor * cinfo->block_size));
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146 compptr->downsampled_height = (JDIMENSION)
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147 jdiv_round_up((long) cinfo->image_height *
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148 (long) (compptr->v_samp_factor * compptr->DCT_v_scaled_size),
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149 (long) (cinfo->max_v_samp_factor * cinfo->block_size));
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152 #endif /* IDCT_SCALING_SUPPORTED */
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154 /* Report number of components in selected colorspace. */
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155 /* Probably this should be in the color conversion module... */
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156 switch (cinfo->out_color_space) {
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157 case JCS_GRAYSCALE:
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158 cinfo->out_color_components = 1;
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161 #if RGB_PIXELSIZE != 3
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162 cinfo->out_color_components = RGB_PIXELSIZE;
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164 #endif /* else share code with YCbCr */
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166 cinfo->out_color_components = 3;
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170 cinfo->out_color_components = 4;
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172 default: /* else must be same colorspace as in file */
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173 cinfo->out_color_components = cinfo->num_components;
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176 cinfo->output_components = (cinfo->quantize_colors ? 1 :
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177 cinfo->out_color_components);
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179 /* See if upsampler will want to emit more than one row at a time */
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180 if (use_merged_upsample(cinfo))
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181 cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
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183 cinfo->rec_outbuf_height = 1;
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188 * Several decompression processes need to range-limit values to the range
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189 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
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190 * due to noise introduced by quantization, roundoff error, etc. These
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191 * processes are inner loops and need to be as fast as possible. On most
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192 * machines, particularly CPUs with pipelines or instruction prefetch,
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193 * a (subscript-check-less) C table lookup
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194 * x = sample_range_limit[x];
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195 * is faster than explicit tests
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196 * if (x < 0) x = 0;
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197 * else if (x > MAXJSAMPLE) x = MAXJSAMPLE;
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198 * These processes all use a common table prepared by the routine below.
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200 * For most steps we can mathematically guarantee that the initial value
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201 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
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202 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial
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203 * limiting step (just after the IDCT), a wildly out-of-range value is
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204 * possible if the input data is corrupt. To avoid any chance of indexing
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205 * off the end of memory and getting a bad-pointer trap, we perform the
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206 * post-IDCT limiting thus:
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207 * x = range_limit[x & MASK];
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208 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
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209 * samples. Under normal circumstances this is more than enough range and
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210 * a correct output will be generated; with bogus input data the mask will
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211 * cause wraparound, and we will safely generate a bogus-but-in-range output.
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212 * For the post-IDCT step, we want to convert the data from signed to unsigned
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213 * representation by adding CENTERJSAMPLE at the same time that we limit it.
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214 * So the post-IDCT limiting table ends up looking like this:
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215 * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
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216 * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
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217 * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
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218 * 0,1,...,CENTERJSAMPLE-1
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219 * Negative inputs select values from the upper half of the table after
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222 * We can save some space by overlapping the start of the post-IDCT table
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223 * with the simpler range limiting table. The post-IDCT table begins at
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224 * sample_range_limit + CENTERJSAMPLE.
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226 * Note that the table is allocated in near data space on PCs; it's small
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227 * enough and used often enough to justify this.
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231 prepare_range_limit_table (j_decompress_ptr cinfo)
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232 /* Allocate and fill in the sample_range_limit table */
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237 table = (JSAMPLE *)
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238 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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239 (5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
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240 table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */
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241 cinfo->sample_range_limit = table;
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242 /* First segment of "simple" table: limit[x] = 0 for x < 0 */
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243 MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE));
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244 /* Main part of "simple" table: limit[x] = x */
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245 for (i = 0; i <= MAXJSAMPLE; i++)
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246 table[i] = (JSAMPLE) i;
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247 table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */
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248 /* End of simple table, rest of first half of post-IDCT table */
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249 for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++)
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250 table[i] = MAXJSAMPLE;
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251 /* Second half of post-IDCT table */
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252 MEMZERO(table + (2 * (MAXJSAMPLE+1)),
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253 (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
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254 MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE),
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255 cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
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260 * Master selection of decompression modules.
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261 * This is done once at jpeg_start_decompress time. We determine
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262 * which modules will be used and give them appropriate initialization calls.
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263 * We also initialize the decompressor input side to begin consuming data.
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265 * Since jpeg_read_header has finished, we know what is in the SOF
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266 * and (first) SOS markers. We also have all the application parameter
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271 master_selection (j_decompress_ptr cinfo)
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273 my_master_ptr master = (my_master_ptr) cinfo->master;
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274 boolean use_c_buffer;
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275 long samplesperrow;
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276 JDIMENSION jd_samplesperrow;
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278 /* Initialize dimensions and other stuff */
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279 jpeg_calc_output_dimensions(cinfo);
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280 prepare_range_limit_table(cinfo);
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282 /* Width of an output scanline must be representable as JDIMENSION. */
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283 samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
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284 jd_samplesperrow = (JDIMENSION) samplesperrow;
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285 if ((long) jd_samplesperrow != samplesperrow)
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286 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
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288 /* Initialize my private state */
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289 master->pass_number = 0;
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290 master->using_merged_upsample = use_merged_upsample(cinfo);
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292 /* Color quantizer selection */
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293 master->quantizer_1pass = NULL;
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294 master->quantizer_2pass = NULL;
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295 /* No mode changes if not using buffered-image mode. */
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296 if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
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297 cinfo->enable_1pass_quant = FALSE;
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298 cinfo->enable_external_quant = FALSE;
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299 cinfo->enable_2pass_quant = FALSE;
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301 if (cinfo->quantize_colors) {
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302 if (cinfo->raw_data_out)
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303 ERREXIT(cinfo, JERR_NOTIMPL);
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304 /* 2-pass quantizer only works in 3-component color space. */
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305 if (cinfo->out_color_components != 3) {
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306 cinfo->enable_1pass_quant = TRUE;
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307 cinfo->enable_external_quant = FALSE;
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308 cinfo->enable_2pass_quant = FALSE;
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309 cinfo->colormap = NULL;
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310 } else if (cinfo->colormap != NULL) {
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311 cinfo->enable_external_quant = TRUE;
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312 } else if (cinfo->two_pass_quantize) {
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313 cinfo->enable_2pass_quant = TRUE;
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315 cinfo->enable_1pass_quant = TRUE;
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318 if (cinfo->enable_1pass_quant) {
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319 #ifdef QUANT_1PASS_SUPPORTED
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320 jinit_1pass_quantizer(cinfo);
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321 master->quantizer_1pass = cinfo->cquantize;
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323 ERREXIT(cinfo, JERR_NOT_COMPILED);
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327 /* We use the 2-pass code to map to external colormaps. */
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328 if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
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329 #ifdef QUANT_2PASS_SUPPORTED
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330 jinit_2pass_quantizer(cinfo);
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331 master->quantizer_2pass = cinfo->cquantize;
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333 ERREXIT(cinfo, JERR_NOT_COMPILED);
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336 /* If both quantizers are initialized, the 2-pass one is left active;
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337 * this is necessary for starting with quantization to an external map.
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341 /* Post-processing: in particular, color conversion first */
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342 if (! cinfo->raw_data_out) {
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343 if (master->using_merged_upsample) {
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344 #ifdef UPSAMPLE_MERGING_SUPPORTED
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345 jinit_merged_upsampler(cinfo); /* does color conversion too */
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347 ERREXIT(cinfo, JERR_NOT_COMPILED);
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350 jinit_color_deconverter(cinfo);
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351 jinit_upsampler(cinfo);
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353 jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
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356 jinit_inverse_dct(cinfo);
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357 /* Entropy decoding: either Huffman or arithmetic coding. */
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358 if (cinfo->arith_code)
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359 jinit_arith_decoder(cinfo);
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361 jinit_huff_decoder(cinfo);
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364 /* Initialize principal buffer controllers. */
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365 use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
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366 jinit_d_coef_controller(cinfo, use_c_buffer);
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368 if (! cinfo->raw_data_out)
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369 jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
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371 /* We can now tell the memory manager to allocate virtual arrays. */
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372 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
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374 /* Initialize input side of decompressor to consume first scan. */
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375 (*cinfo->inputctl->start_input_pass) (cinfo);
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377 #ifdef D_MULTISCAN_FILES_SUPPORTED
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378 /* If jpeg_start_decompress will read the whole file, initialize
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379 * progress monitoring appropriately. The input step is counted
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382 if (cinfo->progress != NULL && ! cinfo->buffered_image &&
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383 cinfo->inputctl->has_multiple_scans) {
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385 /* Estimate number of scans to set pass_limit. */
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386 if (cinfo->progressive_mode) {
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387 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
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388 nscans = 2 + 3 * cinfo->num_components;
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390 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
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391 nscans = cinfo->num_components;
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393 cinfo->progress->pass_counter = 0L;
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394 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
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395 cinfo->progress->completed_passes = 0;
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396 cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
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397 /* Count the input pass as done */
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398 master->pass_number++;
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400 #endif /* D_MULTISCAN_FILES_SUPPORTED */
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406 * This is called at the beginning of each output pass. We determine which
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407 * modules will be active during this pass and give them appropriate
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408 * start_pass calls. We also set is_dummy_pass to indicate whether this
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409 * is a "real" output pass or a dummy pass for color quantization.
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410 * (In the latter case, jdapistd.c will crank the pass to completion.)
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414 prepare_for_output_pass (j_decompress_ptr cinfo)
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416 my_master_ptr master = (my_master_ptr) cinfo->master;
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418 if (master->pub.is_dummy_pass) {
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419 #ifdef QUANT_2PASS_SUPPORTED
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420 /* Final pass of 2-pass quantization */
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421 master->pub.is_dummy_pass = FALSE;
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422 (*cinfo->cquantize->start_pass) (cinfo, FALSE);
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423 (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
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424 (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
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426 ERREXIT(cinfo, JERR_NOT_COMPILED);
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427 #endif /* QUANT_2PASS_SUPPORTED */
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429 if (cinfo->quantize_colors && cinfo->colormap == NULL) {
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430 /* Select new quantization method */
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431 if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
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432 cinfo->cquantize = master->quantizer_2pass;
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433 master->pub.is_dummy_pass = TRUE;
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434 } else if (cinfo->enable_1pass_quant) {
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435 cinfo->cquantize = master->quantizer_1pass;
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437 ERREXIT(cinfo, JERR_MODE_CHANGE);
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440 (*cinfo->idct->start_pass) (cinfo);
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441 (*cinfo->coef->start_output_pass) (cinfo);
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442 if (! cinfo->raw_data_out) {
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443 if (! master->using_merged_upsample)
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444 (*cinfo->cconvert->start_pass) (cinfo);
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445 (*cinfo->upsample->start_pass) (cinfo);
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446 if (cinfo->quantize_colors)
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447 (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
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448 (*cinfo->post->start_pass) (cinfo,
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449 (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
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450 (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
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454 /* Set up progress monitor's pass info if present */
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455 if (cinfo->progress != NULL) {
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456 cinfo->progress->completed_passes = master->pass_number;
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457 cinfo->progress->total_passes = master->pass_number +
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458 (master->pub.is_dummy_pass ? 2 : 1);
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459 /* In buffered-image mode, we assume one more output pass if EOI not
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460 * yet reached, but no more passes if EOI has been reached.
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462 if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
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463 cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
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470 * Finish up at end of an output pass.
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474 finish_output_pass (j_decompress_ptr cinfo)
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476 my_master_ptr master = (my_master_ptr) cinfo->master;
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478 if (cinfo->quantize_colors)
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479 (*cinfo->cquantize->finish_pass) (cinfo);
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480 master->pass_number++;
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484 #ifdef D_MULTISCAN_FILES_SUPPORTED
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487 * Switch to a new external colormap between output passes.
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491 jpeg_new_colormap (j_decompress_ptr cinfo)
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493 my_master_ptr master = (my_master_ptr) cinfo->master;
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495 /* Prevent application from calling me at wrong times */
\r
496 if (cinfo->global_state != DSTATE_BUFIMAGE)
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497 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
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499 if (cinfo->quantize_colors && cinfo->enable_external_quant &&
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500 cinfo->colormap != NULL) {
\r
501 /* Select 2-pass quantizer for external colormap use */
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502 cinfo->cquantize = master->quantizer_2pass;
\r
503 /* Notify quantizer of colormap change */
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504 (*cinfo->cquantize->new_color_map) (cinfo);
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505 master->pub.is_dummy_pass = FALSE; /* just in case */
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507 ERREXIT(cinfo, JERR_MODE_CHANGE);
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510 #endif /* D_MULTISCAN_FILES_SUPPORTED */
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514 * Initialize master decompression control and select active modules.
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515 * This is performed at the start of jpeg_start_decompress.
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519 jinit_master_decompress (j_decompress_ptr cinfo)
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521 my_master_ptr master;
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523 master = (my_master_ptr)
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524 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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525 SIZEOF(my_decomp_master));
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526 cinfo->master = (struct jpeg_decomp_master *) master;
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527 master->pub.prepare_for_output_pass = prepare_for_output_pass;
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528 master->pub.finish_output_pass = finish_output_pass;
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530 master->pub.is_dummy_pass = FALSE;
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532 master_selection(cinfo);
\r