transupp.c

jpeg文件压缩、解压

    for (ci = 0; ci < info->num_components; ci++) {
      compptr = srcinfo->comp_info + ci;
      coef_arrays[ci] = (*srcinfo->mem->request_virt_barray)
	((j_common_ptr) srcinfo, JPOOL_IMAGE, FALSE,
	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
				(long) compptr->v_samp_factor),
	 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
				(long) compptr->h_samp_factor),
	 (JDIMENSION) compptr->h_samp_factor);
    }
    break;
  }
  info->workspace_coef_arrays = coef_arrays;
}


/* Transpose destination image parameters */

LOCAL(void)
transpose_critical_parameters (j_compress_ptr dstinfo)
{
  int tblno, i, j, ci, itemp;
  jpeg_component_info *compptr;
  JQUANT_TBL *qtblptr;
  JDIMENSION dtemp;
  UINT16 qtemp;

  /* Transpose basic image dimensions */
  dtemp = dstinfo->image_width;
  dstinfo->image_width = dstinfo->image_height;
  dstinfo->image_height = dtemp;

  /* Transpose sampling factors */
  for (ci = 0; ci < dstinfo->num_components; ci++) {
    compptr = dstinfo->comp_info + ci;
    itemp = compptr->h_samp_factor;
    compptr->h_samp_factor = compptr->v_samp_factor;
    compptr->v_samp_factor = itemp;
  }

  /* Transpose quantization tables */
  for (tblno = 0; tblno < NUM_QUANT_TBLS; tblno++) {
    qtblptr = dstinfo->quant_tbl_ptrs[tblno];
    if (qtblptr != NULL) {
      for (i = 0; i < DCTSIZE; i++) {
	for (j = 0; j < i; j++) {
	  qtemp = qtblptr->quantval[i*DCTSIZE+j];
	  qtblptr->quantval[i*DCTSIZE+j] = qtblptr->quantval[j*DCTSIZE+i];
	  qtblptr->quantval[j*DCTSIZE+i] = qtemp;
	}
      }
    }
  }
}


/* Trim off any partial iMCUs on the indicated destination edge */

LOCAL(void)
trim_right_edge (j_compress_ptr dstinfo)
{
  int ci, max_h_samp_factor;
  JDIMENSION MCU_cols;

  /* We have to compute max_h_samp_factor ourselves,
   * because it hasn't been set yet in the destination
   * (and we don't want to use the source's value).
   */
  max_h_samp_factor = 1;
  for (ci = 0; ci < dstinfo->num_components; ci++) {
    int h_samp_factor = dstinfo->comp_info[ci].h_samp_factor;
    max_h_samp_factor = MAX(max_h_samp_factor, h_samp_factor);
  }
  MCU_cols = dstinfo->image_width / (max_h_samp_factor * DCTSIZE);
  if (MCU_cols > 0)		/* can't trim to 0 pixels */
    dstinfo->image_width = MCU_cols * (max_h_samp_factor * DCTSIZE);
}

LOCAL(void)
trim_bottom_edge (j_compress_ptr dstinfo)
{
  int ci, max_v_samp_factor;
  JDIMENSION MCU_rows;

  /* We have to compute max_v_samp_factor ourselves,
   * because it hasn't been set yet in the destination
   * (and we don't want to use the source's value).
   */
  max_v_samp_factor = 1;
  for (ci = 0; ci < dstinfo->num_components; ci++) {
    int v_samp_factor = dstinfo->comp_info[ci].v_samp_factor;
    max_v_samp_factor = MAX(max_v_samp_factor, v_samp_factor);
  }
  MCU_rows = dstinfo->image_height / (max_v_samp_factor * DCTSIZE);
  if (MCU_rows > 0)		/* can't trim to 0 pixels */
    dstinfo->image_height = MCU_rows * (max_v_samp_factor * DCTSIZE);
}


/* Adjust output image parameters as needed.
 *
 * This must be called after jpeg_copy_critical_parameters()
 * and before jpeg_write_coefficients().
 *
 * The return value is the set of virtual coefficient arrays to be written
 * (either the ones allocated by jtransform_request_workspace, or the
 * original source data arrays).  The caller will need to pass this value
 * to jpeg_write_coefficients().
 */

GLOBAL(jvirt_barray_ptr *)
jtransform_adjust_parameters (j_decompress_ptr srcinfo,
			      j_compress_ptr dstinfo,
			      jvirt_barray_ptr *src_coef_arrays,
			      jpeg_transform_info *info)
{
  /* If force-to-grayscale is requested, adjust destination parameters */
  if (info->force_grayscale) {
    /* We use jpeg_set_colorspace to make sure subsidiary settings get fixed
     * properly.  Among other things, the target h_samp_factor & v_samp_factor
     * will get set to 1, which typically won't match the source.
     * In fact we do this even if the source is already grayscale; that
     * provides an easy way of coercing a grayscale JPEG with funny sampling
     * factors to the customary 1,1.  (Some decoders fail on other factors.)
     */
    if ((dstinfo->jpeg_color_space == JCS_YCbCr &&
	 dstinfo->num_components == 3) ||
	(dstinfo->jpeg_color_space == JCS_GRAYSCALE &&
	 dstinfo->num_components == 1)) {
      /* We have to preserve the source's quantization table number. */
      int sv_quant_tbl_no = dstinfo->comp_info[0].quant_tbl_no;
      jpeg_set_colorspace(dstinfo, JCS_GRAYSCALE);
      dstinfo->comp_info[0].quant_tbl_no = sv_quant_tbl_no;
    } else {
      /* Sorry, can't do it */
      ERREXIT(dstinfo, JERR_CONVERSION_NOTIMPL);
    }
  }

  /* Correct the destination's image dimensions etc if necessary */
  switch (info->transform) {
  case JXFORM_NONE:
    /* Nothing to do */
    break;
  case JXFORM_FLIP_H:
    if (info->trim)
      trim_right_edge(dstinfo);
    break;
  case JXFORM_FLIP_V:
    if (info->trim)
      trim_bottom_edge(dstinfo);
    break;
  case JXFORM_TRANSPOSE:
    transpose_critical_parameters(dstinfo);
    /* transpose does NOT have to trim anything */
    break;
  case JXFORM_TRANSVERSE:
    transpose_critical_parameters(dstinfo);
    if (info->trim) {
      trim_right_edge(dstinfo);
      trim_bottom_edge(dstinfo);
    }
    break;
  case JXFORM_ROT_90:
    transpose_critical_parameters(dstinfo);
    if (info->trim)
      trim_right_edge(dstinfo);
    break;
  case JXFORM_ROT_180:
    if (info->trim) {
      trim_right_edge(dstinfo);
      trim_bottom_edge(dstinfo);
    }
    break;
  case JXFORM_ROT_270:
    transpose_critical_parameters(dstinfo);
    if (info->trim)
      trim_bottom_edge(dstinfo);
    break;
  }

  /* Return the appropriate output data set */
  if (info->workspace_coef_arrays != NULL)
    return info->workspace_coef_arrays;
  return src_coef_arrays;
}


/* Execute the actual transformation, if any.
 *
 * This must be called *after* jpeg_write_coefficients, because it depends
 * on jpeg_write_coefficients to have computed subsidiary values such as
 * the per-component width and height fields in the destination object.
 *
 * Note that some transformations will modify the source data arrays!
 */

GLOBAL(void)
jtransform_execute_transformation (j_decompress_ptr srcinfo,
				   j_compress_ptr dstinfo,
				   jvirt_barray_ptr *src_coef_arrays,
				   jpeg_transform_info *info)
{
  jvirt_barray_ptr *dst_coef_arrays = info->workspace_coef_arrays;

  switch (info->transform) {
  case JXFORM_NONE:
    break;
  case JXFORM_FLIP_H:
    do_flip_h(srcinfo, dstinfo, src_coef_arrays);
    break;
  case JXFORM_FLIP_V:
    do_flip_v(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSPOSE:
    do_transpose(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSVERSE:
    do_transverse(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_90:
    do_rot_90(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_180:
    do_rot_180(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_270:
    do_rot_270(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
    break;
  }
}

#endif /* TRANSFORMS_SUPPORTED */


/* Setup decompression object to save desired markers in memory.
 * This must be called before jpeg_read_header() to have the desired effect.
 */

GLOBAL(void)
jcopy_markers_setup (j_decompress_ptr srcinfo, JCOPY_OPTION option)
{
#ifdef SAVE_MARKERS_SUPPORTED
  int m;

  /* Save comments except under NONE option */
  if (option != JCOPYOPT_NONE) {
    jpeg_save_markers(srcinfo, JPEG_COM, 0xFFFF);
  }
  /* Save all types of APPn markers iff ALL option */
  if (option == JCOPYOPT_ALL) {
    for (m = 0; m < 16; m++)
      jpeg_save_markers(srcinfo, JPEG_APP0 + m, 0xFFFF);
  }
#endif /* SAVE_MARKERS_SUPPORTED */
}

/* Copy markers saved in the given source object to the destination object.
 * This should be called just after jpeg_start_compress() or
 * jpeg_write_coefficients().
 * Note that those routines will have written the SOI, and also the
 * JFIF APP0 or Adobe APP14 markers if selected.
 */

GLOBAL(void)
jcopy_markers_execute (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
		       JCOPY_OPTION option)
{
  jpeg_saved_marker_ptr marker;

  /* In the current implementation, we don't actually need to examine the
   * option flag here; we just copy everything that got saved.
   * But to avoid confusion, we do not output JFIF and Adobe APP14 markers
   * if the encoder library already wrote one.
   */
  for (marker = srcinfo->marker_list; marker != NULL; marker = marker->next) {
    if (dstinfo->write_JFIF_header &&
	marker->marker == JPEG_APP0 &&
	marker->data_length >= 5 &&
	GETJOCTET(marker->data[0]) == 0x4A &&
	GETJOCTET(marker->data[1]) == 0x46 &&
	GETJOCTET(marker->data[2]) == 0x49 &&
	GETJOCTET(marker->data[3]) == 0x46 &&
	GETJOCTET(marker->data[4]) == 0)
      continue;			/* reject duplicate JFIF */
    if (dstinfo->write_Adobe_marker &&
	marker->marker == JPEG_APP0+14 &&
	marker->data_length >= 5 &&
	GETJOCTET(marker->data[0]) == 0x41 &&
	GETJOCTET(marker->data[1]) == 0x64 &&
	GETJOCTET(marker->data[2]) == 0x6F &&
	GETJOCTET(marker->data[3]) == 0x62 &&
	GETJOCTET(marker->data[4]) == 0x65)
      continue;			/* reject duplicate Adobe */
#ifdef NEED_FAR_POINTERS
    /* We could use jpeg_write_marker if the data weren't FAR... */
    {
      unsigned int i;
      jpeg_write_m_header(dstinfo, marker->marker, marker->data_length);
      for (i = 0; i < marker->data_length; i++)
	jpeg_write_m_byte(dstinfo, marker->data[i]);
    }
#else
    jpeg_write_marker(dstinfo, marker->marker,
		      marker->data, marker->data_length);
#endif
  }
}