/* Adjust Exif image parameters.
 *
 * We try to adjust the Tags ExifImageWidth and ExifImageHeight if possible.
 */

LOCAL(void)
adjust_exif_parameters (JOCTET FAR * data, unsigned int length,
			JDIMENSION new_width, JDIMENSION new_height)
{
  boolean is_motorola; /* Flag for byte order */
  unsigned int number_of_tags, tagnum;
  unsigned int firstoffset, offset;
  JDIMENSION new_value;

  if (length < 12) return; /* Length of an IFD entry */

  /* Discover byte order */
  if (GETJOCTET(data[0]) == 0x49 && GETJOCTET(data[1]) == 0x49)
    is_motorola = FALSE;
  else if (GETJOCTET(data[0]) == 0x4D && GETJOCTET(data[1]) == 0x4D)
    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) {
    /* 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;
  }

  /* 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;
}