pjs/image/decoders/iccjpeg.c

/*
 * iccprofile.c
 *
 * This file provides code to read and write International Color Consortium
 * (ICC) device profiles embedded in JFIF JPEG image files.  The ICC has
 * defined a standard format for including such data in JPEG "APP2" markers.
 * The code given here does not know anything about the internal structure
 * of the ICC profile data; it just knows how to put the profile data into
 * a JPEG file being written, or get it back out when reading.
 *
 * This code depends on new features added to the IJG JPEG library as of
 * IJG release 6b; it will not compile or work with older IJG versions.
 *
 * NOTE: this code would need surgery to work on 16-bit-int machines
 * with ICC profiles exceeding 64K bytes in size.  If you need to do that,
 * change all the "unsigned int" variables to "INT32".  You'll also need
 * to find a malloc() replacement that can allocate more than 64K.
 */

#include "iccjpeg.h"
#include <stdlib.h>			/* define malloc() */


/*
 * Since an ICC profile can be larger than the maximum size of a JPEG marker
 * (64K), we need provisions to split it into multiple markers.  The format
 * defined by the ICC specifies one or more APP2 markers containing the
 * following data:
 *	Identifying string	ASCII "ICC_PROFILE\0"  (12 bytes)
 *	Marker sequence number	1 for first APP2, 2 for next, etc (1 byte)
 *	Number of markers	Total number of APP2's used (1 byte)
 *      Profile data		(remainder of APP2 data)
 * Decoders should use the marker sequence numbers to reassemble the profile,
 * rather than assuming that the APP2 markers appear in the correct sequence.
 */

#define ICC_MARKER  (JPEG_APP0 + 2)	/* JPEG marker code for ICC */
#define ICC_OVERHEAD_LEN  14		/* size of non-profile data in APP2 */
#define MAX_BYTES_IN_MARKER  65533	/* maximum data len of a JPEG marker */
#define MAX_DATA_BYTES_IN_MARKER  (MAX_BYTES_IN_MARKER - ICC_OVERHEAD_LEN)

/*
 * Prepare for reading an ICC profile
 */

void
setup_read_icc_profile (j_decompress_ptr cinfo)
{
  /* Tell the library to keep any APP2 data it may find */
  jpeg_save_markers(cinfo, ICC_MARKER, 0xFFFF);
}


/*
 * Handy subroutine to test whether a saved marker is an ICC profile marker.
 */

static boolean
marker_is_icc (jpeg_saved_marker_ptr marker)
{
  return
    marker->marker == ICC_MARKER &&
    marker->data_length >= ICC_OVERHEAD_LEN &&
    /* verify the identifying string */
    GETJOCTET(marker->data[0]) == 0x49 &&
    GETJOCTET(marker->data[1]) == 0x43 &&
    GETJOCTET(marker->data[2]) == 0x43 &&
    GETJOCTET(marker->data[3]) == 0x5F &&
    GETJOCTET(marker->data[4]) == 0x50 &&
    GETJOCTET(marker->data[5]) == 0x52 &&
    GETJOCTET(marker->data[6]) == 0x4F &&
    GETJOCTET(marker->data[7]) == 0x46 &&
    GETJOCTET(marker->data[8]) == 0x49 &&
    GETJOCTET(marker->data[9]) == 0x4C &&
    GETJOCTET(marker->data[10]) == 0x45 &&
    GETJOCTET(marker->data[11]) == 0x0;
}


/*
 * See if there was an ICC profile in the JPEG file being read;
 * if so, reassemble and return the profile data.
 *
 * TRUE is returned if an ICC profile was found, FALSE if not.
 * If TRUE is returned, *icc_data_ptr is set to point to the
 * returned data, and *icc_data_len is set to its length.
 *
 * IMPORTANT: the data at **icc_data_ptr has been allocated with malloc()
 * and must be freed by the caller with free() when the caller no longer
 * needs it.  (Alternatively, we could write this routine to use the
 * IJG library's memory allocator, so that the data would be freed implicitly
 * at jpeg_finish_decompress() time.  But it seems likely that many apps
 * will prefer to have the data stick around after decompression finishes.)
 *
 * NOTE: if the file contains invalid ICC APP2 markers, we just silently
 * return FALSE.  You might want to issue an error message instead.
 */

boolean
read_icc_profile (j_decompress_ptr cinfo,
		  JOCTET **icc_data_ptr,
		  unsigned int *icc_data_len)
{
  jpeg_saved_marker_ptr marker;
  int num_markers = 0;
  int seq_no;
  JOCTET *icc_data;
  unsigned int total_length;
#define MAX_SEQ_NO  255		/* sufficient since marker numbers are bytes */
  char marker_present[MAX_SEQ_NO+1];	  /* 1 if marker found */
  unsigned int data_length[MAX_SEQ_NO+1]; /* size of profile data in marker */
  unsigned int data_offset[MAX_SEQ_NO+1]; /* offset for data in marker */

  *icc_data_ptr = NULL;		/* avoid confusion if FALSE return */
  *icc_data_len = 0;

  /* This first pass over the saved markers discovers whether there are
   * any ICC markers and verifies the consistency of the marker numbering.
   */

  for (seq_no = 1; seq_no <= MAX_SEQ_NO; seq_no++)
    marker_present[seq_no] = 0;

  for (marker = cinfo->marker_list; marker != NULL; marker = marker->next) {
    if (marker_is_icc(marker)) {
      if (num_markers == 0)
	num_markers = GETJOCTET(marker->data[13]);
      else if (num_markers != GETJOCTET(marker->data[13]))
	return FALSE;		/* inconsistent num_markers fields */
      seq_no = GETJOCTET(marker->data[12]);
      if (seq_no <= 0 || seq_no > num_markers)
	return FALSE;		/* bogus sequence number */
      if (marker_present[seq_no])
	return FALSE;		/* duplicate sequence numbers */
      marker_present[seq_no] = 1;
      data_length[seq_no] = marker->data_length - ICC_OVERHEAD_LEN;
    }
  }

  if (num_markers == 0)
    return FALSE;

  /* Check for missing markers, count total space needed,
   * compute offset of each marker's part of the data.
   */

  total_length = 0;
  for (seq_no = 1; seq_no <= num_markers; seq_no++) {
    if (marker_present[seq_no] == 0)
      return FALSE;		/* missing sequence number */
    data_offset[seq_no] = total_length;
    total_length += data_length[seq_no];
  }

  if (total_length <= 0)
    return FALSE;		/* found only empty markers? */

  /* Allocate space for assembled data */
  icc_data = (JOCTET *) malloc(total_length * sizeof(JOCTET));
  if (icc_data == NULL)
    return FALSE;		/* oops, out of memory */

  /* and fill it in */
  for (marker = cinfo->marker_list; marker != NULL; marker = marker->next) {
    if (marker_is_icc(marker)) {
      JOCTET FAR *src_ptr;
      JOCTET *dst_ptr;
      unsigned int length;
      seq_no = GETJOCTET(marker->data[12]);
      dst_ptr = icc_data + data_offset[seq_no];
      src_ptr = marker->data + ICC_OVERHEAD_LEN;
      length = data_length[seq_no];
      while (length--) {
	*dst_ptr++ = *src_ptr++;
      }
    }
  }

  *icc_data_ptr = icc_data;
  *icc_data_len = total_length;

  return TRUE;
}