jdmaster.c

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/*
 * jdmaster.c
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Modified 2002-2025 by Guido Vollbeding.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains master control logic for the JPEG decompressor.
 * These routines are concerned with selecting the modules to be executed
 * and with determining the number of passes and the work to be done in each
 * pass.
 */
 
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
 
 
/* Private state */
 
typedef struct {
  struct jpeg_decomp_master pub; /* public fields */
 
  int pass_number;      /* # of passes completed */
 
  boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
 
  /* Saved references to initialized quantizer modules,
   * in case we need to switch modes.
   */
  struct jpeg_color_quantizer * quantizer_1pass;
  struct jpeg_color_quantizer * quantizer_2pass;
} my_decomp_master;
 
typedef my_decomp_master * my_master_ptr;
 
 
/*
 * Determine whether merged upsample/color conversion should be used.
 * CRUCIAL: this must match the actual capabilities of jdmerge.c!
 */
 
LOCAL(boolean)
use_merged_upsample (j_decompress_ptr cinfo)
{
#ifdef UPSAMPLE_MERGING_SUPPORTED
  /* Merging is the equivalent of plain box-filter upsampling. */
  /* The following condition is only needed if fancy shall select
   * a different upsampling method.  In our current implementation
   * fancy only affects the DCT scaling, thus we can use fancy
   * upsampling and merged upsample simultaneously, in particular
   * with scaled DCT sizes larger than the default DCTSIZE.
   */
#if 0
  if (cinfo->do_fancy_upsampling)
    return FALSE;
#endif
  if (cinfo->CCIR601_sampling)
    return FALSE;
  /* jdmerge.c only supports YCC=>RGB color conversion */
  if ((cinfo->jpeg_color_space != JCS_YCbCr &&
       cinfo->jpeg_color_space != JCS_BG_YCC) ||
      cinfo->num_components != 3 ||
      cinfo->out_color_space != JCS_RGB ||
      cinfo->out_color_components != RGB_PIXELSIZE ||
      cinfo->color_transform)
    return FALSE;
  /* and it only handles 2h1v or 2h2v sampling ratios */
  if (cinfo->comp_info[0].h_samp_factor != 2 ||
      cinfo->comp_info[1].h_samp_factor != 1 ||
      cinfo->comp_info[2].h_samp_factor != 1 ||
      cinfo->comp_info[0].v_samp_factor >  2 ||
      cinfo->comp_info[1].v_samp_factor != 1 ||
      cinfo->comp_info[2].v_samp_factor != 1)
    return FALSE;
  /* furthermore, it doesn't work if we've scaled the IDCTs differently */
  if (cinfo->comp_info[0].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
      cinfo->comp_info[1].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
      cinfo->comp_info[2].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
      cinfo->comp_info[0].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
      cinfo->comp_info[1].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
      cinfo->comp_info[2].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size)
    return FALSE;
  /* ??? also need to test for upsample-time rescaling, when & if supported */
  return TRUE;          /* by golly, it'll work... */
#else
  return FALSE;
#endif
}
 
 
/*
 * Compute output image dimensions and related values.
 * NOTE: this is exported for possible use by application.
 * Hence it mustn't do anything that can't be done twice.
 * Also note that it may be called before the master module is initialized!
 */
 
GLOBAL(void)
jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
/* Do computations that are needed before master selection phase.
 * This function is used for full decompression.
 */
{
  int ci, i;
  jpeg_component_info *compptr;
 
  /* Prevent application from calling me at wrong times */
  if (cinfo->global_state != DSTATE_READY)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
 
  /* Compute core output image dimensions and DCT scaling choices. */
  jpeg_core_output_dimensions(cinfo);
 
#ifdef IDCT_SCALING_SUPPORTED
 
  /* In selecting the actual DCT scaling for each component, we try to
   * scale up the chroma components via IDCT scaling rather than upsampling.
   * This saves time if the upsampler gets to use 1:1 scaling.
   * Note this code adapts subsampling ratios which are powers of 2.
   */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    int ssize = 1;
    if (! cinfo->raw_data_out)
      while (cinfo->min_DCT_h_scaled_size * ssize <=
         (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
         (cinfo->max_h_samp_factor % (compptr->h_samp_factor * ssize * 2)) ==
         0) {
    ssize = ssize * 2;
      }
    compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size * ssize;
    ssize = 1;
    if (! cinfo->raw_data_out)
      while (cinfo->min_DCT_v_scaled_size * ssize <=
         (cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
         (cinfo->max_v_samp_factor % (compptr->v_samp_factor * ssize * 2)) ==
         0) {
    ssize = ssize * 2;
      }
    compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size * ssize;
 
    /* We don't support IDCT ratios larger than 2. */
    if (compptr->DCT_h_scaled_size > compptr->DCT_v_scaled_size * 2)
    compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size * 2;
    else if (compptr->DCT_v_scaled_size > compptr->DCT_h_scaled_size * 2)
    compptr->DCT_v_scaled_size = compptr->DCT_h_scaled_size * 2;
 
    /* Recompute downsampled dimensions of components;
     * application needs to know these if using raw downsampled data.
     */
    /* Size in samples, after IDCT scaling */
    compptr->downsampled_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width *
            (long) (compptr->h_samp_factor * compptr->DCT_h_scaled_size),
            (long) (cinfo->max_h_samp_factor * cinfo->block_size));
    compptr->downsampled_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height *
            (long) (compptr->v_samp_factor * compptr->DCT_v_scaled_size),
            (long) (cinfo->max_v_samp_factor * cinfo->block_size));
  }
 
#endif /* IDCT_SCALING_SUPPORTED */
 
  /* Report number of components in selected colorspace. */
  /* This should correspond to the actual code in the color conversion module. */
  switch (cinfo->out_color_space) {
  case JCS_GRAYSCALE:
    cinfo->out_color_components = 1;
    break;
  case JCS_RGB:
  case JCS_BG_RGB:
    cinfo->out_color_components = RGB_PIXELSIZE;
    break;
  default:  /* YCCK <=> CMYK conversion or same colorspace as in file */
    i = 0;
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     ci++, compptr++)
      if (compptr->component_needed)
    i++;    /* count output color components */
    cinfo->out_color_components = i;
  }
  cinfo->output_components = (cinfo->quantize_colors ? 1 :
                  cinfo->out_color_components);
 
  /* See if upsampler will want to emit more than one row at a time */
  if (use_merged_upsample(cinfo))
    cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
  else
    cinfo->rec_outbuf_height = 1;
}
 
 
/*
 * Several decompression processes need to range-limit values to the range
 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
 * due to noise introduced by quantization, roundoff error, etc.  These
 * processes are inner loops and need to be as fast as possible.  On most
 * machines, particularly CPUs with pipelines or instruction prefetch,
 * a (subscript-check-less) C table lookup
 *      x = sample_range_limit[x];
 * is faster than explicit tests
 *      if (x < 0)  x = 0;
 *      else if (x > MAXJSAMPLE)  x = MAXJSAMPLE;
 * These processes all use a common table prepared by the routine below.
 *
 * For most steps we can mathematically guarantee that the initial value
 * of x is within 2*(MAXJSAMPLE+1) of the legal range, so a table running
 * from -2*(MAXJSAMPLE+1) to 3*MAXJSAMPLE+2 is sufficient.  But for the
 * initial limiting step (just after the IDCT), a wildly out-of-range value
 * is possible if the input data is corrupt.  To avoid any chance of indexing
 * off the end of memory and getting a bad-pointer trap, we perform the
 * post-IDCT limiting thus:
 *      x = (sample_range_limit - SUBSET)[(x + CENTER) & MASK];
 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
 * samples.  Under normal circumstances this is more than enough range and
 * a correct output will be generated; with bogus input data the mask will
 * cause wraparound, and we will safely generate a bogus-but-in-range output.
 * For the post-IDCT step, we want to convert the data from signed to unsigned
 * representation by adding CENTERJSAMPLE at the same time that we limit it.
 * This is accomplished with SUBSET = CENTER - CENTERJSAMPLE.
 *
 * Note that the table is allocated in near data space on PCs; it's small
 * enough and used often enough to justify this.
 */
 
LOCAL(void)
prepare_range_limit_table (j_decompress_ptr cinfo)
/* Allocate and fill in the sample_range_limit table */
{
  JSAMPLE * table;
  int i;
 
  table = (JSAMPLE *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo,
    JPOOL_IMAGE, (RANGE_CENTER * 2 + MAXJSAMPLE + 1) * SIZEOF(JSAMPLE));
  /* First segment of range limit table: limit[x] = 0 for x < 0 */
  MEMZERO(table, RANGE_CENTER * SIZEOF(JSAMPLE));
  table += RANGE_CENTER;    /* allow negative subscripts of table */
  cinfo->sample_range_limit = table;
  /* Main part of range limit table: limit[x] = x */
  for (i = 0; i <= MAXJSAMPLE; i++)
    table[i] = (JSAMPLE) i;
  /* End of range limit table: limit[x] = MAXJSAMPLE for x > MAXJSAMPLE */
  for (; i <=  MAXJSAMPLE + RANGE_CENTER; i++)
    table[i] = MAXJSAMPLE;
}
 
 
/*
 * Master selection of decompression modules.
 * This is done once at jpeg_start_decompress time.  We determine
 * which modules will be used and give them appropriate initialization calls.
 * We also initialize the decompressor input side to begin consuming data.
 *
 * Since jpeg_read_header has finished, we know what is in the SOF
 * and (first) SOS markers.  We also have all the application parameter
 * settings.
 */
 
LOCAL(void)
master_selection (j_decompress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;
  boolean use_c_buffer;
  long samplesperrow;
  JDIMENSION jd_samplesperrow;
 
  /* For now, precision must match compiled-in value... */
  if (cinfo->data_precision != JPEG_DATA_PRECISION)
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
 
  /* Initialize dimensions and other stuff */
  jpeg_calc_output_dimensions(cinfo);
  prepare_range_limit_table(cinfo);
 
  /* Sanity check on image dimensions */
  if (cinfo->output_height <= 0 || cinfo->output_width <= 0 ||
      cinfo->out_color_components <= 0)
    ERREXIT(cinfo, JERR_EMPTY_IMAGE);
 
  /* Width of an output scanline must be representable as JDIMENSION. */
  samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
  jd_samplesperrow = (JDIMENSION) samplesperrow;
  if ((long) jd_samplesperrow != samplesperrow)
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
 
  /* Initialize my private state */
  master->pass_number = 0;
  master->using_merged_upsample = use_merged_upsample(cinfo);
 
  /* Color quantizer selection */
  master->quantizer_1pass = NULL;
  master->quantizer_2pass = NULL;
  /* No mode changes if not using buffered-image mode. */
  if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
    cinfo->enable_1pass_quant = FALSE;
    cinfo->enable_external_quant = FALSE;
    cinfo->enable_2pass_quant = FALSE;
  }
  if (cinfo->quantize_colors) {
    if (cinfo->raw_data_out)
      ERREXIT(cinfo, JERR_NOTIMPL);
    /* 2-pass quantizer only works in 3-component color space. */
    if (cinfo->out_color_components != 3) {
      cinfo->enable_1pass_quant = TRUE;
      cinfo->enable_external_quant = FALSE;
      cinfo->enable_2pass_quant = FALSE;
      cinfo->colormap = NULL;
    } else if (cinfo->colormap != NULL) {
      cinfo->enable_external_quant = TRUE;
    } else if (cinfo->two_pass_quantize) {
      cinfo->enable_2pass_quant = TRUE;
    } else {
      cinfo->enable_1pass_quant = TRUE;
    }
 
    if (cinfo->enable_1pass_quant) {
#ifdef QUANT_1PASS_SUPPORTED
      jinit_1pass_quantizer(cinfo);
      master->quantizer_1pass = cinfo->cquantize;
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
    }
 
    /* We use the 2-pass code to map to external colormaps. */
    if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
#ifdef QUANT_2PASS_SUPPORTED
      jinit_2pass_quantizer(cinfo);
      master->quantizer_2pass = cinfo->cquantize;
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
    }
    /* If both quantizers are initialized, the 2-pass one is left active;
     * this is necessary for starting with quantization to an external map.
     */
  }
 
  /* Post-processing: in particular, color conversion first */
  if (! cinfo->raw_data_out) {
    if (master->using_merged_upsample) {
#ifdef UPSAMPLE_MERGING_SUPPORTED
      jinit_merged_upsampler(cinfo); /* does color conversion too */
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
    } else {
      jinit_color_deconverter(cinfo);
      jinit_upsampler(cinfo);
    }
    jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
  }
  /* Inverse DCT */
  jinit_inverse_dct(cinfo);
  /* Entropy decoding: either Huffman or arithmetic coding. */
  if (cinfo->arith_code)
    jinit_arith_decoder(cinfo);
  else {
    jinit_huff_decoder(cinfo);
  }
 
  /* Initialize principal buffer controllers. */
  use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
  jinit_d_coef_controller(cinfo, use_c_buffer);
 
  if (! cinfo->raw_data_out)
    jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
 
  /* We can now tell the memory manager to allocate virtual arrays. */
  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
 
  /* Initialize input side of decompressor to consume first scan. */
  (*cinfo->inputctl->start_input_pass) (cinfo);
 
#ifdef D_MULTISCAN_FILES_SUPPORTED
  /* If jpeg_start_decompress will read the whole file, initialize
   * progress monitoring appropriately.  The input step is counted
   * as one pass.
   */
  if (cinfo->progress != NULL && ! cinfo->buffered_image &&
      cinfo->inputctl->has_multiple_scans) {
    int nscans;
    /* Estimate number of scans to set pass_limit. */
    if (cinfo->progressive_mode) {
      /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
      nscans = 2 + 3 * cinfo->num_components;
    } else {
      /* For a nonprogressive multiscan file, estimate 1 scan per component. */
      nscans = cinfo->num_components;
    }
    cinfo->progress->pass_counter = 0L;
    cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
    cinfo->progress->completed_passes = 0;
    cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
    /* Count the input pass as done */
    master->pass_number++;
  }
#endif /* D_MULTISCAN_FILES_SUPPORTED */
}
 
 
/*
 * Per-pass setup.
 * This is called at the beginning of each output pass.  We determine which
 * modules will be active during this pass and give them appropriate
 * start_pass calls.  We also set is_dummy_pass to indicate whether this
 * is a "real" output pass or a dummy pass for color quantization.
 * (In the latter case, jdapistd.c will crank the pass to completion.)
 */
 
METHODDEF(void)
prepare_for_output_pass (j_decompress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;
 
  if (master->pub.is_dummy_pass) {
#ifdef QUANT_2PASS_SUPPORTED
    /* Final pass of 2-pass quantization */
    master->pub.is_dummy_pass = FALSE;
    (*cinfo->cquantize->start_pass) (cinfo, FALSE);
    (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
    (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif /* QUANT_2PASS_SUPPORTED */
  } else {
    if (cinfo->quantize_colors && cinfo->colormap == NULL) {
      /* Select new quantization method */
      if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
    cinfo->cquantize = master->quantizer_2pass;
    master->pub.is_dummy_pass = TRUE;
      } else if (cinfo->enable_1pass_quant) {
    cinfo->cquantize = master->quantizer_1pass;
      } else {
    ERREXIT(cinfo, JERR_MODE_CHANGE);
      }
    }
    (*cinfo->idct->start_pass) (cinfo);
    (*cinfo->coef->start_output_pass) (cinfo);
    if (! cinfo->raw_data_out) {
      if (! master->using_merged_upsample)
    (*cinfo->cconvert->start_pass) (cinfo);
      (*cinfo->upsample->start_pass) (cinfo);
      if (cinfo->quantize_colors)
    (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
      (*cinfo->post->start_pass) (cinfo,
        (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
      (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
    }
  }
 
  /* Set up progress monitor's pass info if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->completed_passes = master->pass_number;
    cinfo->progress->total_passes = master->pass_number +
                    (master->pub.is_dummy_pass ? 2 : 1);
    /* In buffered-image mode, we assume one more output pass if EOI not
     * yet reached, but no more passes if EOI has been reached.
     */
    if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
      cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
    }
  }
}
 
 
/*
 * Finish up at end of an output pass.
 */
 
METHODDEF(void)
finish_output_pass (j_decompress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;
 
  if (cinfo->quantize_colors)
    (*cinfo->cquantize->finish_pass) (cinfo);
  master->pass_number++;
}
 
 
#ifdef D_MULTISCAN_FILES_SUPPORTED
 
/*
 * Switch to a new external colormap between output passes.
 */
 
GLOBAL(void)
jpeg_new_colormap (j_decompress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;
 
  /* Prevent application from calling me at wrong times */
  if (cinfo->global_state != DSTATE_BUFIMAGE)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
 
  if (cinfo->quantize_colors && cinfo->enable_external_quant &&
      cinfo->colormap != NULL) {
    /* Select 2-pass quantizer for external colormap use */
    cinfo->cquantize = master->quantizer_2pass;
    /* Notify quantizer of colormap change */
    (*cinfo->cquantize->new_color_map) (cinfo);
    master->pub.is_dummy_pass = FALSE; /* just in case */
  } else
    ERREXIT(cinfo, JERR_MODE_CHANGE);
}
 
#endif /* D_MULTISCAN_FILES_SUPPORTED */
 
 
/*
 * Initialize master decompression control and select active modules.
 * This is performed at the start of jpeg_start_decompress.
 */
 
GLOBAL(void)
jinit_master_decompress (j_decompress_ptr cinfo)
{
  my_master_ptr master;
 
  master = (my_master_ptr) (*cinfo->mem->alloc_small)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_decomp_master));
  cinfo->master = &master->pub;
  master->pub.prepare_for_output_pass = prepare_for_output_pass;
  master->pub.finish_output_pass = finish_output_pass;
 
  master->pub.is_dummy_pass = FALSE;
 
  master_selection(cinfo);
}