jcmaster.c

其中包括图像压缩的基本编码方法如Huffman编码算术编码JPEG 2000H.261压缩编码标准小波变换编码运动估计算法视频图象采集的VC实现等.

/* Do computations that are needed before processing a JPEG scan */
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] are already set */
{
  int ci, mcublks, tmp;
  jpeg_component_info *compptr;
  
  if (cinfo->comps_in_scan == 1) {
    
    /* Noninterleaved (single-component) scan */
    compptr = cinfo->cur_comp_info[0];
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = compptr->width_in_blocks;
    cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
    
    /* For noninterleaved scan, always one block per MCU */
    compptr->MCU_width = 1;
    compptr->MCU_height = 1;
    compptr->MCU_blocks = 1;
    compptr->MCU_sample_width = DCTSIZE;
    compptr->last_col_width = 1;
    /* For noninterleaved scans, it is convenient to define last_row_height
     * as the number of block rows present in the last iMCU row.
     */
    tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    if (tmp == 0) tmp = compptr->v_samp_factor;
    compptr->last_row_height = tmp;
    
    /* Prepare array describing MCU composition */
    cinfo->blocks_in_MCU = 1;
    cinfo->MCU_membership[0] = 0;
    
  } else {
    
    /* Interleaved (multi-component) scan */
    if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
	       MAX_COMPS_IN_SCAN);
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width,
		    (long) (cinfo->max_h_samp_factor*DCTSIZE));
    cinfo->MCU_rows_in_scan = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height,
		    (long) (cinfo->max_v_samp_factor*DCTSIZE));
    
    cinfo->blocks_in_MCU = 0;
    
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Sampling factors give # of blocks of component in each MCU */
      compptr->MCU_width = compptr->h_samp_factor;
      compptr->MCU_height = compptr->v_samp_factor;
      compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
      compptr->MCU_sample_width = compptr->MCU_width * DCTSIZE;
      /* Figure number of non-dummy blocks in last MCU column & row */
      tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
      if (tmp == 0) tmp = compptr->MCU_width;
      compptr->last_col_width = tmp;
      tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
      if (tmp == 0) tmp = compptr->MCU_height;
      compptr->last_row_height = tmp;
      /* Prepare array describing MCU composition */
      mcublks = compptr->MCU_blocks;
      if (cinfo->blocks_in_MCU + mcublks > C_MAX_BLOCKS_IN_MCU)
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
      while (mcublks-- > 0) {
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
      }
    }
    
  }

  /* Convert restart specified in rows to actual MCU count. */
  /* Note that count must fit in 16 bits, so we provide limiting. */
  if (cinfo->restart_in_rows > 0) {
    long nominal = (long) cinfo->restart_in_rows * (long) cinfo->MCUs_per_row;
    cinfo->restart_interval = (unsigned int) MIN(nominal, 65535L);
  }
}


/*
 * Per-pass setup.
 * This is called at the beginning of each pass.  We determine which modules
 * will be active during this pass and give them appropriate start_pass calls.
 * We also set is_last_pass to indicate whether any more passes will be
 * required.
 */

METHODDEF(void)
prepare_for_pass (j_compress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;

  switch (master->pass_type) {
  case main_pass:
    /* Initial pass: will collect input data, and do either Huffman
     * optimization or data output for the first scan.
     */
    select_scan_parameters(cinfo);
    per_scan_setup(cinfo);
    if (! cinfo->raw_data_in) {
      (*cinfo->cconvert->start_pass) (cinfo);
      (*cinfo->downsample->start_pass) (cinfo);
      (*cinfo->prep->start_pass) (cinfo, JBUF_PASS_THRU);
    }
    (*cinfo->fdct->start_pass) (cinfo);
    (*cinfo->entropy->start_pass) (cinfo, cinfo->optimize_coding);
    (*cinfo->coef->start_pass) (cinfo,
				(master->total_passes > 1 ?
				 JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
    (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
    if (cinfo->optimize_coding) {
      /* No immediate data output; postpone writing frame/scan headers */
      master->pub.call_pass_startup = FALSE;
    } else {
      /* Will write frame/scan headers at first jpeg_write_scanlines call */
      master->pub.call_pass_startup = TRUE;
    }
    break;
#ifdef ENTROPY_OPT_SUPPORTED
  case huff_opt_pass:
    /* Do Huffman optimization for a scan after the first one. */
    select_scan_parameters(cinfo);
    per_scan_setup(cinfo);
    if (cinfo->Ss != 0 || cinfo->Ah == 0 || cinfo->arith_code) {
      (*cinfo->entropy->start_pass) (cinfo, TRUE);
      (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
      master->pub.call_pass_startup = FALSE;
      break;
    }
    /* Special case: Huffman DC refinement scans need no Huffman table
     * and therefore we can skip the optimization pass for them.
     */
    master->pass_type = output_pass;
    master->pass_number++;
    /*FALLTHROUGH*/
#endif
  case output_pass:
    /* Do a data-output pass. */
    /* We need not repeat per-scan setup if prior optimization pass did it. */
    if (! cinfo->optimize_coding) {
      select_scan_parameters(cinfo);
      per_scan_setup(cinfo);
    }
    (*cinfo->entropy->start_pass) (cinfo, FALSE);
    (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
    /* We emit frame/scan headers now */
    if (master->scan_number == 0)
      (*cinfo->marker->write_frame_header) (cinfo);
    (*cinfo->marker->write_scan_header) (cinfo);
    master->pub.call_pass_startup = FALSE;
    break;
  default:
    ERREXIT(cinfo, JERR_NOT_COMPILED);
  }

  master->pub.is_last_pass = (master->pass_number == master->total_passes-1);

  /* 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->total_passes;
  }
}


/*
 * Special start-of-pass hook.
 * This is called by jpeg_write_scanlines if call_pass_startup is TRUE.
 * In single-pass processing, we need this hook because we don't want to
 * write frame/scan headers during jpeg_start_compress; we want to let the
 * application write COM markers etc. between jpeg_start_compress and the
 * jpeg_write_scanlines loop.
 * In multi-pass processing, this routine is not used.
 */

METHODDEF(void)
pass_startup (j_compress_ptr cinfo)
{
  cinfo->master->call_pass_startup = FALSE; /* reset flag so call only once */

  (*cinfo->marker->write_frame_header) (cinfo);
  (*cinfo->marker->write_scan_header) (cinfo);
}


/*
 * Finish up at end of pass.
 */

METHODDEF(void)
finish_pass_master (j_compress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;

  /* The entropy coder always needs an end-of-pass call,
   * either to analyze statistics or to flush its output buffer.
   */
  (*cinfo->entropy->finish_pass) (cinfo);

  /* Update state for next pass */
  switch (master->pass_type) {
  case main_pass:
    /* next pass is either output of scan 0 (after optimization)
     * or output of scan 1 (if no optimization).
     */
    master->pass_type = output_pass;
    if (! cinfo->optimize_coding)
      master->scan_number++;
    break;
  case huff_opt_pass:
    /* next pass is always output of current scan */
    master->pass_type = output_pass;
    break;
  case output_pass:
    /* next pass is either optimization or output of next scan */
    if (cinfo->optimize_coding)
      master->pass_type = huff_opt_pass;
    master->scan_number++;
    break;
  }

  master->pass_number++;
}


/*
 * Initialize master compression control.
 */

GLOBAL(void)
jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
{
  my_master_ptr master;

  master = (my_master_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  SIZEOF(my_comp_master));
  cinfo->master = (struct jpeg_comp_master *) master;
  master->pub.prepare_for_pass = prepare_for_pass;
  master->pub.pass_startup = pass_startup;
  master->pub.finish_pass = finish_pass_master;
  master->pub.is_last_pass = FALSE;

  /* Validate parameters, determine derived values */
  initial_setup(cinfo);

  if (cinfo->scan_info != NULL) {
#ifdef C_MULTISCAN_FILES_SUPPORTED
    validate_script(cinfo);
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
  } else {
    cinfo->progressive_mode = FALSE;
    cinfo->num_scans = 1;
  }

  if (cinfo->progressive_mode)	/*  TEMPORARY HACK ??? */
    cinfo->optimize_coding = TRUE; /* assume default tables no good for progressive mode */

  /* Initialize my private state */
  if (transcode_only) {
    /* no main pass in transcoding */
    if (cinfo->optimize_coding)
      master->pass_type = huff_opt_pass;
    else
      master->pass_type = output_pass;
  } else {
    /* for normal compression, first pass is always this type: */
    master->pass_type = main_pass;
  }
  master->scan_number = 0;
  master->pass_number = 0;
  if (cinfo->optimize_coding)
    master->total_passes = cinfo->num_scans * 2;
  else
    master->total_passes = cinfo->num_scans;
}