src/jpeg/jdmaster.c

   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 }