1 /* 2 * jdmaster.c 3 * 4 * Copyright (C) 1991-1997, Thomas G. Lane. 5 * This file is part of the Independent JPEG Group's software. 6 * For conditions of distribution and use, see the accompanying README file. 7 * 8 * This file contains master control logic for the JPEG decompressor. 9 * These routines are concerned with selecting the modules to be executed 10 * and with determining the number of passes and the work to be done in each 11 * pass. 12 */ 13 14 #define JPEG_INTERNALS 15 #include "jinclude.h" 16 #include "jpeglib.h" 17 18 19 /* Private state */ 20 21 typedef struct { 22 struct jpeg_decomp_master pub; /* public fields */ 23 24 int pass_number; /* # of passes completed */ 25 26 boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */ 27 28 /* Saved references to initialized quantizer modules, 29 * in case we need to switch modes. 30 */ 31 struct jpeg_color_quantizer * quantizer_1pass; 32 struct jpeg_color_quantizer * quantizer_2pass; 33 } my_decomp_master; 34 35 typedef my_decomp_master * my_master_ptr; 36 37 38 /* 39 * Determine whether merged upsample/color conversion should be used. 40 * CRUCIAL: this must match the actual capabilities of jdmerge.c! 41 */ 42 43 LOCAL(boolean) 44 use_merged_upsample (j_decompress_ptr cinfo) 45 { 46 #ifdef UPSAMPLE_MERGING_SUPPORTED 47 /* Merging is the equivalent of plain box-filter upsampling */ 48 if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling) 49 return FALSE; 50 51 #ifdef ANDROID_RGB 52 /* jdmerge.c only supports YCC=>RGB565 and YCC=>RGB color conversion */ 53 if (cinfo->jpeg_color_space != JCS_YCbCr || 54 cinfo->num_components != 3 || 55 cinfo->out_color_components != 3 || 56 (cinfo->out_color_space != JCS_RGB_565 && 57 cinfo->out_color_space != JCS_RGB)) { 58 return FALSE; 59 } 60 #else 61 /* jdmerge.c only supports YCC=>RGB color conversion */ 62 if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 || 63 cinfo->out_color_space != JCS_RGB || 64 cinfo->out_color_components != RGB_PIXELSIZE) 65 return FALSE; 66 #endif 67 68 /* and it only handles 2h1v or 2h2v sampling ratios */ 69 if (cinfo->comp_info[0].h_samp_factor != 2 || 70 cinfo->comp_info[1].h_samp_factor != 1 || 71 cinfo->comp_info[2].h_samp_factor != 1 || 72 cinfo->comp_info[0].v_samp_factor > 2 || 73 cinfo->comp_info[1].v_samp_factor != 1 || 74 cinfo->comp_info[2].v_samp_factor != 1) 75 return FALSE; 76 /* furthermore, it doesn't work if we've scaled the IDCTs differently */ 77 if (cinfo->comp_info[0].DCT_scaled_size != cinfo->min_DCT_scaled_size || 78 cinfo->comp_info[1].DCT_scaled_size != cinfo->min_DCT_scaled_size || 79 cinfo->comp_info[2].DCT_scaled_size != cinfo->min_DCT_scaled_size) 80 return FALSE; 81 /* ??? also need to test for upsample-time rescaling, when & if supported */ 82 return TRUE; /* by golly, it'll work... */ 83 #else 84 return FALSE; 85 #endif 86 } 87 88 89 /* 90 * Compute output image dimensions and related values. 91 * NOTE: this is exported for possible use by application. 92 * Hence it mustn't do anything that can't be done twice. 93 * Also note that it may be called before the master module is initialized! 94 */ 95 96 GLOBAL(void) 97 jpeg_calc_output_dimensions (j_decompress_ptr cinfo) 98 /* Do computations that are needed before master selection phase */ 99 { 100 #ifdef IDCT_SCALING_SUPPORTED 101 int ci; 102 jpeg_component_info *compptr; 103 #endif 104 105 /* Prevent application from calling me at wrong times */ 106 #if ANDROID_TILE_BASED_DECODE 107 // Tile based decoding may call this function several times. 108 if (!cinfo->tile_decode) 109 #endif 110 if (cinfo->global_state != DSTATE_READY) 111 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 112 113 #ifdef IDCT_SCALING_SUPPORTED 114 115 /* Compute actual output image dimensions and DCT scaling choices. */ 116 if (cinfo->scale_num * 8 <= cinfo->scale_denom) { 117 /* Provide 1/8 scaling */ 118 cinfo->output_width = (JDIMENSION) 119 jdiv_round_up((long) cinfo->image_width, 8L); 120 cinfo->output_height = (JDIMENSION) 121 jdiv_round_up((long) cinfo->image_height, 8L); 122 cinfo->min_DCT_scaled_size = 1; 123 } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) { 124 /* Provide 1/4 scaling */ 125 cinfo->output_width = (JDIMENSION) 126 jdiv_round_up((long) cinfo->image_width, 4L); 127 cinfo->output_height = (JDIMENSION) 128 jdiv_round_up((long) cinfo->image_height, 4L); 129 cinfo->min_DCT_scaled_size = 2; 130 } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) { 131 /* Provide 1/2 scaling */ 132 cinfo->output_width = (JDIMENSION) 133 jdiv_round_up((long) cinfo->image_width, 2L); 134 cinfo->output_height = (JDIMENSION) 135 jdiv_round_up((long) cinfo->image_height, 2L); 136 cinfo->min_DCT_scaled_size = 4; 137 } else { 138 /* Provide 1/1 scaling */ 139 cinfo->output_width = cinfo->image_width; 140 cinfo->output_height = cinfo->image_height; 141 cinfo->min_DCT_scaled_size = DCTSIZE; 142 } 143 /* In selecting the actual DCT scaling for each component, we try to 144 * scale up the chroma components via IDCT scaling rather than upsampling. 145 * This saves time if the upsampler gets to use 1:1 scaling. 146 * Note this code assumes that the supported DCT scalings are powers of 2. 147 */ 148 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 149 ci++, compptr++) { 150 int ssize = cinfo->min_DCT_scaled_size; 151 while (ssize < DCTSIZE && 152 (compptr->h_samp_factor * ssize * 2 <= 153 cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) && 154 (compptr->v_samp_factor * ssize * 2 <= 155 cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) { 156 ssize = ssize * 2; 157 } 158 compptr->DCT_scaled_size = ssize; 159 } 160 161 /* Recompute downsampled dimensions of components; 162 * application needs to know these if using raw downsampled data. 163 */ 164 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 165 ci++, compptr++) { 166 /* Size in samples, after IDCT scaling */ 167 compptr->downsampled_width = (JDIMENSION) 168 jdiv_round_up((long) cinfo->image_width * 169 (long) (compptr->h_samp_factor * compptr->DCT_scaled_size), 170 (long) (cinfo->max_h_samp_factor * DCTSIZE)); 171 compptr->downsampled_height = (JDIMENSION) 172 jdiv_round_up((long) cinfo->image_height * 173 (long) (compptr->v_samp_factor * compptr->DCT_scaled_size), 174 (long) (cinfo->max_v_samp_factor * DCTSIZE)); 175 } 176 177 #else /* !IDCT_SCALING_SUPPORTED */ 178 179 /* Hardwire it to "no scaling" */ 180 cinfo->output_width = cinfo->image_width; 181 cinfo->output_height = cinfo->image_height; 182 /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE, 183 * and has computed unscaled downsampled_width and downsampled_height. 184 */ 185 186 #endif /* IDCT_SCALING_SUPPORTED */ 187 188 /* Report number of components in selected colorspace. */ 189 /* Probably this should be in the color conversion module... */ 190 switch (cinfo->out_color_space) { 191 case JCS_GRAYSCALE: 192 cinfo->out_color_components = 1; 193 break; 194 case JCS_RGB: 195 #if RGB_PIXELSIZE != 3 196 cinfo->out_color_components = RGB_PIXELSIZE; 197 break; 198 #endif /* else share code with YCbCr */ 199 #ifdef ANDROID_RGB 200 case JCS_RGB_565: 201 #endif 202 case JCS_YCbCr: 203 cinfo->out_color_components = 3; 204 break; 205 case JCS_CMYK: 206 case JCS_YCCK: 207 #ifdef ANDROID_RGB 208 case JCS_RGBA_8888: 209 #endif 210 cinfo->out_color_components = 4; 211 break; 212 default: /* else must be same colorspace as in file */ 213 cinfo->out_color_components = cinfo->num_components; 214 break; 215 } 216 cinfo->output_components = (cinfo->quantize_colors ? 1 : 217 cinfo->out_color_components); 218 219 /* See if upsampler will want to emit more than one row at a time */ 220 if (use_merged_upsample(cinfo)) 221 cinfo->rec_outbuf_height = cinfo->max_v_samp_factor; 222 else 223 cinfo->rec_outbuf_height = 1; 224 } 225 226 227 /* 228 * Several decompression processes need to range-limit values to the range 229 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range 230 * due to noise introduced by quantization, roundoff error, etc. These 231 * processes are inner loops and need to be as fast as possible. On most 232 * machines, particularly CPUs with pipelines or instruction prefetch, 233 * a (subscript-check-less) C table lookup 234 * x = sample_range_limit[x]; 235 * is faster than explicit tests 236 * if (x < 0) x = 0; 237 * else if (x > MAXJSAMPLE) x = MAXJSAMPLE; 238 * These processes all use a common table prepared by the routine below. 239 * 240 * For most steps we can mathematically guarantee that the initial value 241 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from 242 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial 243 * limiting step (just after the IDCT), a wildly out-of-range value is 244 * possible if the input data is corrupt. To avoid any chance of indexing 245 * off the end of memory and getting a bad-pointer trap, we perform the 246 * post-IDCT limiting thus: 247 * x = range_limit[x & MASK]; 248 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit 249 * samples. Under normal circumstances this is more than enough range and 250 * a correct output will be generated; with bogus input data the mask will 251 * cause wraparound, and we will safely generate a bogus-but-in-range output. 252 * For the post-IDCT step, we want to convert the data from signed to unsigned 253 * representation by adding CENTERJSAMPLE at the same time that we limit it. 254 * So the post-IDCT limiting table ends up looking like this: 255 * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE, 256 * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), 257 * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), 258 * 0,1,...,CENTERJSAMPLE-1 259 * Negative inputs select values from the upper half of the table after 260 * masking. 261 * 262 * We can save some space by overlapping the start of the post-IDCT table 263 * with the simpler range limiting table. The post-IDCT table begins at 264 * sample_range_limit + CENTERJSAMPLE. 265 * 266 * Note that the table is allocated in near data space on PCs; it's small 267 * enough and used often enough to justify this. 268 */ 269 270 LOCAL(void) 271 prepare_range_limit_table (j_decompress_ptr cinfo) 272 /* Allocate and fill in the sample_range_limit table */ 273 { 274 JSAMPLE * table; 275 int i; 276 277 table = (JSAMPLE *) 278 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 279 (5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE)); 280 table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */ 281 cinfo->sample_range_limit = table; 282 /* First segment of "simple" table: limit[x] = 0 for x < 0 */ 283 MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE)); 284 /* Main part of "simple" table: limit[x] = x */ 285 for (i = 0; i <= MAXJSAMPLE; i++) 286 table[i] = (JSAMPLE) i; 287 table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */ 288 /* End of simple table, rest of first half of post-IDCT table */ 289 for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++) 290 table[i] = MAXJSAMPLE; 291 /* Second half of post-IDCT table */ 292 MEMZERO(table + (2 * (MAXJSAMPLE+1)), 293 (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE)); 294 MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE), 295 cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE)); 296 } 297 298 299 /* 300 * Master selection of decompression modules. 301 * This is done once at jpeg_start_decompress time. We determine 302 * which modules will be used and give them appropriate initialization calls. 303 * We also initialize the decompressor input side to begin consuming data. 304 * 305 * Since jpeg_read_header has finished, we know what is in the SOF 306 * and (first) SOS markers. We also have all the application parameter 307 * settings. 308 */ 309 310 LOCAL(void) 311 master_selection (j_decompress_ptr cinfo) 312 { 313 my_master_ptr master = (my_master_ptr) cinfo->master; 314 boolean use_c_buffer; 315 long samplesperrow; 316 JDIMENSION jd_samplesperrow; 317 318 /* Initialize dimensions and other stuff */ 319 jpeg_calc_output_dimensions(cinfo); 320 prepare_range_limit_table(cinfo); 321 322 /* Width of an output scanline must be representable as JDIMENSION. */ 323 samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components; 324 jd_samplesperrow = (JDIMENSION) samplesperrow; 325 if ((long) jd_samplesperrow != samplesperrow) 326 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); 327 328 /* Initialize my private state */ 329 master->pass_number = 0; 330 master->using_merged_upsample = use_merged_upsample(cinfo); 331 332 /* Color quantizer selection */ 333 master->quantizer_1pass = NULL; 334 master->quantizer_2pass = NULL; 335 /* No mode changes if not using buffered-image mode. */ 336 if (! cinfo->quantize_colors || ! cinfo->buffered_image) { 337 cinfo->enable_1pass_quant = FALSE; 338 cinfo->enable_external_quant = FALSE; 339 cinfo->enable_2pass_quant = FALSE; 340 } 341 if (cinfo->quantize_colors) { 342 if (cinfo->raw_data_out) 343 ERREXIT(cinfo, JERR_NOTIMPL); 344 /* 2-pass quantizer only works in 3-component color space. */ 345 if (cinfo->out_color_components != 3) { 346 cinfo->enable_1pass_quant = TRUE; 347 cinfo->enable_external_quant = FALSE; 348 cinfo->enable_2pass_quant = FALSE; 349 cinfo->colormap = NULL; 350 } else if (cinfo->colormap != NULL) { 351 cinfo->enable_external_quant = TRUE; 352 } else if (cinfo->two_pass_quantize) { 353 cinfo->enable_2pass_quant = TRUE; 354 } else { 355 cinfo->enable_1pass_quant = TRUE; 356 } 357 358 if (cinfo->enable_1pass_quant) { 359 #ifdef QUANT_1PASS_SUPPORTED 360 jinit_1pass_quantizer(cinfo); 361 master->quantizer_1pass = cinfo->cquantize; 362 #else 363 ERREXIT(cinfo, JERR_NOT_COMPILED); 364 #endif 365 } 366 367 /* We use the 2-pass code to map to external colormaps. */ 368 if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) { 369 #ifdef QUANT_2PASS_SUPPORTED 370 jinit_2pass_quantizer(cinfo); 371 master->quantizer_2pass = cinfo->cquantize; 372 #else 373 ERREXIT(cinfo, JERR_NOT_COMPILED); 374 #endif 375 } 376 /* If both quantizers are initialized, the 2-pass one is left active; 377 * this is necessary for starting with quantization to an external map. 378 */ 379 } 380 381 /* Post-processing: in particular, color conversion first */ 382 if (! cinfo->raw_data_out) { 383 if (master->using_merged_upsample) { 384 #ifdef UPSAMPLE_MERGING_SUPPORTED 385 jinit_merged_upsampler(cinfo); /* does color conversion too */ 386 #else 387 ERREXIT(cinfo, JERR_NOT_COMPILED); 388 #endif 389 } else { 390 jinit_color_deconverter(cinfo); 391 jinit_upsampler(cinfo); 392 } 393 jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant); 394 } 395 /* Inverse DCT */ 396 jinit_inverse_dct(cinfo); 397 /* Entropy decoding: either Huffman or arithmetic coding. */ 398 if (cinfo->arith_code) { 399 ERREXIT(cinfo, JERR_ARITH_NOTIMPL); 400 } else { 401 if (cinfo->progressive_mode) { 402 #ifdef D_PROGRESSIVE_SUPPORTED 403 jinit_phuff_decoder(cinfo); 404 #else 405 ERREXIT(cinfo, JERR_NOT_COMPILED); 406 #endif 407 } else 408 jinit_huff_decoder(cinfo); 409 } 410 411 /* Initialize principal buffer controllers. */ 412 use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image; 413 jinit_d_coef_controller(cinfo, use_c_buffer); 414 415 if (! cinfo->raw_data_out) 416 jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */); 417 418 /* We can now tell the memory manager to allocate virtual arrays. */ 419 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo); 420 421 /* Initialize input side of decompressor to consume first scan. */ 422 (*cinfo->inputctl->start_input_pass) (cinfo); 423 424 #ifdef D_MULTISCAN_FILES_SUPPORTED 425 /* If jpeg_start_decompress will read the whole file, initialize 426 * progress monitoring appropriately. The input step is counted 427 * as one pass. 428 */ 429 if (cinfo->progress != NULL && ! cinfo->buffered_image && 430 cinfo->inputctl->has_multiple_scans) { 431 int nscans; 432 /* Estimate number of scans to set pass_limit. */ 433 if (cinfo->progressive_mode) { 434 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */ 435 nscans = 2 + 3 * cinfo->num_components; 436 } else { 437 /* For a nonprogressive multiscan file, estimate 1 scan per component. */ 438 nscans = cinfo->num_components; 439 } 440 cinfo->progress->pass_counter = 0L; 441 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans; 442 cinfo->progress->completed_passes = 0; 443 cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2); 444 /* Count the input pass as done */ 445 master->pass_number++; 446 } 447 #endif /* D_MULTISCAN_FILES_SUPPORTED */ 448 } 449 450 451 /* 452 * Per-pass setup. 453 * This is called at the beginning of each output pass. We determine which 454 * modules will be active during this pass and give them appropriate 455 * start_pass calls. We also set is_dummy_pass to indicate whether this 456 * is a "real" output pass or a dummy pass for color quantization. 457 * (In the latter case, jdapistd.c will crank the pass to completion.) 458 */ 459 460 METHODDEF(void) 461 prepare_for_output_pass (j_decompress_ptr cinfo) 462 { 463 my_master_ptr master = (my_master_ptr) cinfo->master; 464 465 if (master->pub.is_dummy_pass) { 466 #ifdef QUANT_2PASS_SUPPORTED 467 /* Final pass of 2-pass quantization */ 468 master->pub.is_dummy_pass = FALSE; 469 (*cinfo->cquantize->start_pass) (cinfo, FALSE); 470 (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST); 471 (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST); 472 #else 473 ERREXIT(cinfo, JERR_NOT_COMPILED); 474 #endif /* QUANT_2PASS_SUPPORTED */ 475 } else { 476 if (cinfo->quantize_colors && cinfo->colormap == NULL) { 477 /* Select new quantization method */ 478 if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) { 479 cinfo->cquantize = master->quantizer_2pass; 480 master->pub.is_dummy_pass = TRUE; 481 } else if (cinfo->enable_1pass_quant) { 482 cinfo->cquantize = master->quantizer_1pass; 483 } else { 484 ERREXIT(cinfo, JERR_MODE_CHANGE); 485 } 486 } 487 (*cinfo->idct->start_pass) (cinfo); 488 (*cinfo->coef->start_output_pass) (cinfo); 489 if (! cinfo->raw_data_out) { 490 if (! master->using_merged_upsample) 491 (*cinfo->cconvert->start_pass) (cinfo); 492 (*cinfo->upsample->start_pass) (cinfo); 493 if (cinfo->quantize_colors) 494 (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass); 495 (*cinfo->post->start_pass) (cinfo, 496 (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU)); 497 (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU); 498 } 499 } 500 501 /* Set up progress monitor's pass info if present */ 502 if (cinfo->progress != NULL) { 503 cinfo->progress->completed_passes = master->pass_number; 504 cinfo->progress->total_passes = master->pass_number + 505 (master->pub.is_dummy_pass ? 2 : 1); 506 /* In buffered-image mode, we assume one more output pass if EOI not 507 * yet reached, but no more passes if EOI has been reached. 508 */ 509 if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) { 510 cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1); 511 } 512 } 513 } 514 515 516 /* 517 * Finish up at end of an output pass. 518 */ 519 520 METHODDEF(void) 521 finish_output_pass (j_decompress_ptr cinfo) 522 { 523 my_master_ptr master = (my_master_ptr) cinfo->master; 524 525 if (cinfo->quantize_colors) 526 (*cinfo->cquantize->finish_pass) (cinfo); 527 master->pass_number++; 528 } 529 530 531 #ifdef D_MULTISCAN_FILES_SUPPORTED 532 533 /* 534 * Switch to a new external colormap between output passes. 535 */ 536 537 GLOBAL(void) 538 jpeg_new_colormap (j_decompress_ptr cinfo) 539 { 540 my_master_ptr master = (my_master_ptr) cinfo->master; 541 542 /* Prevent application from calling me at wrong times */ 543 if (cinfo->global_state != DSTATE_BUFIMAGE) 544 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 545 546 if (cinfo->quantize_colors && cinfo->enable_external_quant && 547 cinfo->colormap != NULL) { 548 /* Select 2-pass quantizer for external colormap use */ 549 cinfo->cquantize = master->quantizer_2pass; 550 /* Notify quantizer of colormap change */ 551 (*cinfo->cquantize->new_color_map) (cinfo); 552 master->pub.is_dummy_pass = FALSE; /* just in case */ 553 } else 554 ERREXIT(cinfo, JERR_MODE_CHANGE); 555 } 556 557 #endif /* D_MULTISCAN_FILES_SUPPORTED */ 558 559 560 /* 561 * Initialize master decompression control and select active modules. 562 * This is performed at the start of jpeg_start_decompress. 563 */ 564 565 GLOBAL(void) 566 jinit_master_decompress (j_decompress_ptr cinfo) 567 { 568 my_master_ptr master; 569 570 master = (my_master_ptr) 571 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 572 SIZEOF(my_decomp_master)); 573 cinfo->master = (struct jpeg_decomp_master *) master; 574 master->pub.prepare_for_output_pass = prepare_for_output_pass; 575 master->pub.finish_output_pass = finish_output_pass; 576 577 master->pub.is_dummy_pass = FALSE; 578 579 master_selection(cinfo); 580 } 581
