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