jccoefct.cpp File Reference

#include "jinclude.h"
#include "jpeglib.h"

Include dependency graph for jccoefct.cpp:

Classes
struct	my_coef_controller

Macros
#define	JPEG_INTERNALS
#define	FULL_COEF_BUFFER_SUPPORTED

Typedefs
typedef my_coef_controller *	my_coef_ptr

Functions
static boolean	compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
static boolean	compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
static boolean	compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
static void	start_iMCU_row (j_compress_ptr cinfo)
static void	start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
void	jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)

Macro Definition Documentation

#define JPEG_INTERNALS

#define FULL_COEF_BUFFER_SUPPORTED

Typedef Documentation

typedef my_coef_controller* my_coef_ptr

Function Documentation

static boolean compress_data ( j_compress_ptr  cinfo, JSAMPIMAGE  input_buf  )

static

{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION MCU_col_num;   /* index of current MCU within row */
  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  int blkn, bi, ci, yindex, yoffset, blockcnt;
  JDIMENSION ypos, xpos;
  jpeg_component_info *compptr;

  /* Loop to write as much as one whole iMCU row */
  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
       yoffset++) {
    for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
     MCU_col_num++) {
      /* Determine where data comes from in input_buf and do the DCT thing.
       * Each call on forward_DCT processes a horizontal row of DCT blocks
       * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
       * sequentially.  Dummy blocks at the right or bottom edge are filled in
       * specially.  The data in them does not matter for image reconstruction,
       * so we fill them with values that will encode to the smallest amount of
       * data, viz: all zeroes in the AC entries, DC entries equal to previous
       * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
       */
      blkn = 0;
      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
                        : compptr->last_col_width;
    xpos = MCU_col_num * compptr->MCU_sample_width;
    ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
    for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
      if (coef->iMCU_row_num < last_iMCU_row ||
          yoffset+yindex < compptr->last_row_height) {
        (*cinfo->fdct->forward_DCT) (cinfo, compptr,
                     input_buf[compptr->component_index],
                     coef->MCU_buffer[blkn],
                     ypos, xpos, (JDIMENSION) blockcnt);
        if (blockcnt < compptr->MCU_width) {
          /* Create some dummy blocks at the right edge of the image. */
          jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
            (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
          for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
        coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
          }
        }
      } else {
        /* Create a row of dummy blocks at the bottom of the image. */
        jzero_far((void FAR *) coef->MCU_buffer[blkn],
              compptr->MCU_width * SIZEOF(JBLOCK));
        for (bi = 0; bi < compptr->MCU_width; bi++) {
          coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
        }
      }
      blkn += compptr->MCU_width;
      ypos += DCTSIZE;
    }
      }
      /* Try to write the MCU.  In event of a suspension failure, we will
       * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
       */
      if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
    /* Suspension forced; update state counters and exit */
    coef->MCU_vert_offset = yoffset;
    coef->mcu_ctr = MCU_col_num;
    return FALSE;
      }
    }
    /* Completed an MCU row, but perhaps not an iMCU row */
    coef->mcu_ctr = 0;
  }
  /* Completed the iMCU row, advance counters for next one */
  coef->iMCU_row_num++;
  start_iMCU_row(cinfo);
  return TRUE;
}

static boolean compress_first_pass ( j_compress_ptr  cinfo, JSAMPIMAGE  input_buf  )

static

{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  JDIMENSION blocks_across, MCUs_across, MCUindex;
  int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
  JCOEF lastDC;
  jpeg_component_info *compptr;
  JBLOCKARRAY buffer;
  JBLOCKROW thisblockrow, lastblockrow;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Align the virtual buffer for this component. */
    buffer = (*cinfo->mem->access_virt_barray)
      ((j_common_ptr) cinfo, coef->whole_image[ci],
       coef->iMCU_row_num * compptr->v_samp_factor,
       (JDIMENSION) compptr->v_samp_factor, TRUE);
    /* Count non-dummy DCT block rows in this iMCU row. */
    if (coef->iMCU_row_num < last_iMCU_row)
      block_rows = compptr->v_samp_factor;
    else {
      /* NB: can't use last_row_height here, since may not be set! */
      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
      if (block_rows == 0) block_rows = compptr->v_samp_factor;
    }
    blocks_across = compptr->width_in_blocks;
    h_samp_factor = compptr->h_samp_factor;
    /* Count number of dummy blocks to be added at the right margin. */
    ndummy = (int) (blocks_across % h_samp_factor);
    if (ndummy > 0)
      ndummy = h_samp_factor - ndummy;
    /* Perform DCT for all non-dummy blocks in this iMCU row.  Each call
     * on forward_DCT processes a complete horizontal row of DCT blocks.
     */
    for (block_row = 0; block_row < block_rows; block_row++) {
      thisblockrow = buffer[block_row];
      (*cinfo->fdct->forward_DCT) (cinfo, compptr,
                   input_buf[ci], thisblockrow,
                   (JDIMENSION) (block_row * DCTSIZE),
                   (JDIMENSION) 0, blocks_across);
      if (ndummy > 0) {
    /* Create dummy blocks at the right edge of the image. */
    thisblockrow += blocks_across; /* => first dummy block */
    jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
    lastDC = thisblockrow[-1][0];
    for (bi = 0; bi < ndummy; bi++) {
      thisblockrow[bi][0] = lastDC;
    }
      }
    }
    /* If at end of image, create dummy block rows as needed.
     * The tricky part here is that within each MCU, we want the DC values
     * of the dummy blocks to match the last real block's DC value.
     * This squeezes a few more bytes out of the resulting file...
     */
    if (coef->iMCU_row_num == last_iMCU_row) {
      blocks_across += ndummy;  /* include lower right corner */
      MCUs_across = blocks_across / h_samp_factor;
      for (block_row = block_rows; block_row < compptr->v_samp_factor;
       block_row++) {
    thisblockrow = buffer[block_row];
    lastblockrow = buffer[block_row-1];
    jzero_far((void FAR *) thisblockrow,
          (size_t) (blocks_across * SIZEOF(JBLOCK)));
    for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
      lastDC = lastblockrow[h_samp_factor-1][0];
      for (bi = 0; bi < h_samp_factor; bi++) {
        thisblockrow[bi][0] = lastDC;
      }
      thisblockrow += h_samp_factor; /* advance to next MCU in row */
      lastblockrow += h_samp_factor;
    }
      }
    }
  }
  /* NB: compress_output will increment iMCU_row_num if successful.
   * A suspension return will result in redoing all the work above next time.
   */

  /* Emit data to the entropy encoder, sharing code with subsequent passes */
  return compress_output(cinfo, input_buf);
}

static boolean compress_output ( j_compress_ptr  cinfo, JSAMPIMAGE  input_buf  )

static

{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION MCU_col_num;   /* index of current MCU within row */
  int blkn, ci, xindex, yindex, yoffset;
  JDIMENSION start_col;
  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
  JBLOCKROW buffer_ptr;
  jpeg_component_info *compptr;

  /* Align the virtual buffers for the components used in this scan.
   * NB: during first pass, this is safe only because the buffers will
   * already be aligned properly, so jmemmgr.c won't need to do any I/O.
   */
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    buffer[ci] = (*cinfo->mem->access_virt_barray)
      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
       coef->iMCU_row_num * compptr->v_samp_factor,
       (JDIMENSION) compptr->v_samp_factor, FALSE);
  }

  /* Loop to process one whole iMCU row */
  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
       yoffset++) {
    for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
     MCU_col_num++) {
      /* Construct list of pointers to DCT blocks belonging to this MCU */
      blkn = 0;         /* index of current DCT block within MCU */
      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    start_col = MCU_col_num * compptr->MCU_width;
    for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
      buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
      for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
        coef->MCU_buffer[blkn++] = buffer_ptr++;
      }
    }
      }
      /* Try to write the MCU. */
      if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
    /* Suspension forced; update state counters and exit */
    coef->MCU_vert_offset = yoffset;
    coef->mcu_ctr = MCU_col_num;
    return FALSE;
      }
    }
    /* Completed an MCU row, but perhaps not an iMCU row */
    coef->mcu_ctr = 0;
  }
  /* Completed the iMCU row, advance counters for next one */
  coef->iMCU_row_num++;
  start_iMCU_row(cinfo);
  return TRUE;
}

static void start_iMCU_row ( j_compress_ptr  cinfo )

static

{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* In an interleaved scan, an MCU row is the same as an iMCU row.
   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
   * But at the bottom of the image, process only what's left.
   */
  if (cinfo->comps_in_scan > 1) {
    coef->MCU_rows_per_iMCU_row = 1;
  } else {
    if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
    else
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  }

  coef->mcu_ctr = 0;
  coef->MCU_vert_offset = 0;
}

static void start_pass_coef ( j_compress_ptr  cinfo, J_BUF_MODE  pass_mode  )

static

{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  coef->iMCU_row_num = 0;
  start_iMCU_row(cinfo);

  switch (pass_mode) {
  case JBUF_PASS_THRU:
    if (coef->whole_image[0] != NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    coef->pub.compress_data = compress_data;
    break;
#ifdef FULL_COEF_BUFFER_SUPPORTED
  case JBUF_SAVE_AND_PASS:
    if (coef->whole_image[0] == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    coef->pub.compress_data = compress_first_pass;
    break;
  case JBUF_CRANK_DEST:
    if (coef->whole_image[0] == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    coef->pub.compress_data = compress_output;
    break;
#endif
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
}

void jinit_c_coef_controller	(	j_compress_ptr	cinfo,
		boolean	need_full_buffer
	)

{
  my_coef_ptr coef;

  coef = (my_coef_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                SIZEOF(my_coef_controller));
  cinfo->coef = (struct jpeg_c_coef_controller *) coef;
  coef->pub.start_pass = start_pass_coef;

  /* Create the coefficient buffer. */
  if (need_full_buffer) {
#ifdef FULL_COEF_BUFFER_SUPPORTED
    /* Allocate a full-image virtual array for each component, */
    /* padded to a multiple of samp_factor DCT blocks in each direction. */
    int ci;
    jpeg_component_info *compptr;

    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     ci++, compptr++) {
      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
     (JDIMENSION) jround_up((long) compptr->width_in_blocks,
                (long) compptr->h_samp_factor),
     (JDIMENSION) jround_up((long) compptr->height_in_blocks,
                (long) compptr->v_samp_factor),
     (JDIMENSION) compptr->v_samp_factor);
    }
#else
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
  } else {
    /* We only need a single-MCU buffer. */
    JBLOCKROW buffer;
    int i;

    buffer = (JBLOCKROW)
      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                  C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
    for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
      coef->MCU_buffer[i] = buffer + i;
    }
    coef->whole_image[0] = NULL; /* flag for no virtual arrays */
  }
}