transupp.c

ＪＰＥＧ图象压缩

    is_motorola = TRUE;
  else
    return;

  /* Check Tag Mark */
  if (is_motorola) {
    if (GETJOCTET(data[2]) != 0) return;
    if (GETJOCTET(data[3]) != 0x2A) return;
  } else {
    if (GETJOCTET(data[3]) != 0) return;
    if (GETJOCTET(data[2]) != 0x2A) return;
  }

  /* Get first IFD offset (offset to IFD0) */
  if (is_motorola) {
    if (GETJOCTET(data[4]) != 0) return;
    if (GETJOCTET(data[5]) != 0) return;
    firstoffset = GETJOCTET(data[6]);
    firstoffset <<= 8;
    firstoffset += GETJOCTET(data[7]);
  } else {
    if (GETJOCTET(data[7]) != 0) return;
    if (GETJOCTET(data[6]) != 0) return;
    firstoffset = GETJOCTET(data[5]);
    firstoffset <<= 8;
    firstoffset += GETJOCTET(data[4]);
  }
  if (firstoffset > length - 2) return; /* check end of data segment */

  /* Get the number of directory entries contained in this IFD */
  if (is_motorola) {
    number_of_tags = GETJOCTET(data[firstoffset]);
    number_of_tags <<= 8;
    number_of_tags += GETJOCTET(data[firstoffset+1]);
  } else {
    number_of_tags = GETJOCTET(data[firstoffset+1]);
    number_of_tags <<= 8;
    number_of_tags += GETJOCTET(data[firstoffset]);
  }
  if (number_of_tags == 0) return;
  firstoffset += 2;

  /* Search for ExifSubIFD offset Tag in IFD0 */
  for (;;) {
    if (firstoffset > length - 12) return; /* check end of data segment */
    /* Get Tag number */
    if (is_motorola) {
      tagnum = GETJOCTET(data[firstoffset]);
      tagnum <<= 8;
      tagnum += GETJOCTET(data[firstoffset+1]);
    } else {
      tagnum = GETJOCTET(data[firstoffset+1]);
      tagnum <<= 8;
      tagnum += GETJOCTET(data[firstoffset]);
    }
    if (tagnum == 0x8769) break; /* found ExifSubIFD offset Tag */
    if (--number_of_tags == 0) return;
    firstoffset += 12;
  }

  /* Get the ExifSubIFD offset */
  if (is_motorola) {
    if (GETJOCTET(data[firstoffset+8]) != 0) return;
    if (GETJOCTET(data[firstoffset+9]) != 0) return;
    offset = GETJOCTET(data[firstoffset+10]);
    offset <<= 8;
    offset += GETJOCTET(data[firstoffset+11]);
  } else {
    if (GETJOCTET(data[firstoffset+11]) != 0) return;
    if (GETJOCTET(data[firstoffset+10]) != 0) return;
    offset = GETJOCTET(data[firstoffset+9]);
    offset <<= 8;
    offset += GETJOCTET(data[firstoffset+8]);
  }
  if (offset > length - 2) return; /* check end of data segment */

  /* Get the number of directory entries contained in this SubIFD */
  if (is_motorola) {
    number_of_tags = GETJOCTET(data[offset]);
    number_of_tags <<= 8;
    number_of_tags += GETJOCTET(data[offset+1]);
  } else {
    number_of_tags = GETJOCTET(data[offset+1]);
    number_of_tags <<= 8;
    number_of_tags += GETJOCTET(data[offset]);
  }
  if (number_of_tags < 2) return;
  offset += 2;

  /* Search for ExifImageWidth and ExifImageHeight Tags in this SubIFD */
  do {
    if (offset > length - 12) return; /* check end of data segment */
    /* Get Tag number */
    if (is_motorola) {
      tagnum = GETJOCTET(data[offset]);
      tagnum <<= 8;
      tagnum += GETJOCTET(data[offset+1]);
    } else {
      tagnum = GETJOCTET(data[offset+1]);
      tagnum <<= 8;
      tagnum += GETJOCTET(data[offset]);
    }
    if (tagnum == 0xA002 || tagnum == 0xA003) {
      if (tagnum == 0xA002)
	new_value = new_width; /* ExifImageWidth Tag */
      else
	new_value = new_height; /* ExifImageHeight Tag */
      if (is_motorola) {
	data[offset+2] = 0; /* Format = unsigned long (4 octets) */
	data[offset+3] = 4;
	data[offset+4] = 0; /* Number Of Components = 1 */
	data[offset+5] = 0;
	data[offset+6] = 0;
	data[offset+7] = 1;
	data[offset+8] = 0;
	data[offset+9] = 0;
	data[offset+10] = (JOCTET)((new_value >> 8) & 0xFF);
	data[offset+11] = (JOCTET)(new_value & 0xFF);
      } else {
	data[offset+2] = 4; /* Format = unsigned long (4 octets) */
	data[offset+3] = 0;
	data[offset+4] = 1; /* Number Of Components = 1 */
	data[offset+5] = 0;
	data[offset+6] = 0;
	data[offset+7] = 0;
	data[offset+8] = (JOCTET)(new_value & 0xFF);
	data[offset+9] = (JOCTET)((new_value >> 8) & 0xFF);
	data[offset+10] = 0;
	data[offset+11] = 0;
      }
    }
    offset += 12;
  } while (--number_of_tags);
}


/* 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) {
    /* First, ensure we have YCbCr or grayscale data, and that the source's
     * Y channel is full resolution.  (No reasonable person would make Y
     * be less than full resolution, so actually coping with that case
     * isn't worth extra code space.  But we check it to avoid crashing.)
     */
    if (((dstinfo->jpeg_color_space == JCS_YCbCr &&
	  dstinfo->num_components == 3) ||
	 (dstinfo->jpeg_color_space == JCS_GRAYSCALE &&
	  dstinfo->num_components == 1)) &&
	srcinfo->comp_info[0].h_samp_factor == srcinfo->max_h_samp_factor &&
	srcinfo->comp_info[0].v_samp_factor == srcinfo->max_v_samp_factor) {
      /* We use jpeg_set_colorspace to make sure subsidiary settings get fixed
       * properly.  Among other things, it sets the target h_samp_factor &
       * v_samp_factor to 1, which typically won't match the source.
       * We have to preserve the source's quantization table number, however.
       */
      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);
    }
  } else if (info->num_components == 1) {
    /* For a single-component source, we force the destination sampling factors
     * to 1x1, with or without force_grayscale.  This is useful because some
     * decoders choke on grayscale images with other sampling factors.
     */
    dstinfo->comp_info[0].h_samp_factor = 1;
    dstinfo->comp_info[0].v_samp_factor = 1;
  }

  /* Correct the destination's image dimensions as necessary
   * for crop and rotate/flip operations.
   */
  dstinfo->image_width = info->output_width;
  dstinfo->image_height = info->output_height;

  /* Transpose destination image parameters */
  switch (info->transform) {
  case JXFORM_TRANSPOSE:
  case JXFORM_TRANSVERSE:
  case JXFORM_ROT_90:
  case JXFORM_ROT_270:
    transpose_critical_parameters(dstinfo);
    break;
  }

  /* Adjust Exif properties */
  if (srcinfo->marker_list != NULL &&
      srcinfo->marker_list->marker == JPEG_APP0+1 &&
      srcinfo->marker_list->data_length >= 6 &&
      GETJOCTET(srcinfo->marker_list->data[0]) == 0x45 &&
      GETJOCTET(srcinfo->marker_list->data[1]) == 0x78 &&
      GETJOCTET(srcinfo->marker_list->data[2]) == 0x69 &&
      GETJOCTET(srcinfo->marker_list->data[3]) == 0x66 &&
      GETJOCTET(srcinfo->marker_list->data[4]) == 0 &&
      GETJOCTET(srcinfo->marker_list->data[5]) == 0) {
    /* Suppress output of JFIF marker */
    dstinfo->write_JFIF_header = FALSE;
    /* Adjust Exif image parameters */
    if (dstinfo->image_width != srcinfo->image_width ||
	dstinfo->image_height != srcinfo->image_height)
      /* Align data segment to start of TIFF structure for parsing */
      adjust_exif_parameters(srcinfo->marker_list->data + 6,
	srcinfo->marker_list->data_length - 6,
	dstinfo->image_width, dstinfo->image_height);
  }

  /* 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_transform (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;

  /* Note: conditions tested here should match those in switch statement
   * in jtransform_request_workspace()
   */
  switch (info->transform) {
  case JXFORM_NONE:
    if (info->x_crop_offset != 0 || info->y_crop_offset != 0)
      do_crop(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_FLIP_H:
    if (info->y_crop_offset != 0)
      do_flip_h(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		src_coef_arrays, dst_coef_arrays);
    else
      do_flip_h_no_crop(srcinfo, dstinfo, info->x_crop_offset,
			src_coef_arrays);
    break;
  case JXFORM_FLIP_V:
    do_flip_v(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSPOSE:
    do_transpose(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		 src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSVERSE:
    do_transverse(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		  src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_90:
    do_rot_90(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_180:
    do_rot_180(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	       src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_270:
    do_rot_270(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	       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
  }
}