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