jcicc.c

/*
 * jcicc.c
 *
 * Copyright (C) 1997-1998, Thomas G. Lane, Todd Newman.
 * Copyright (C) 2017, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file provides code to write International Color Consortium (ICC) device
 * profiles embedded in JFIF JPEG image files.  The ICC has defined a standard
 * 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 embed the profile data in a JPEG file while writing it.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jerror.h"


/*
 * 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)


/*
 * This routine writes the given ICC profile data into a JPEG file.  It *must*
 * be called AFTER calling jpeg_start_compress() and BEFORE the first call to
 * jpeg_write_scanlines().  (This ordering ensures that the APP2 marker(s) will
 * appear after the SOI and JFIF or Adobe markers, but before all else.)
 */

GLOBAL(void)
jpeg_write_icc_profile(j_compress_ptr cinfo, const JOCTET *icc_data_ptr,
                       unsigned int icc_data_len)
{
  unsigned int num_markers;     /* total number of markers we'll write */
  int cur_marker = 1;           /* per spec, counting starts at 1 */
  unsigned int length;          /* number of bytes to write in this marker */

  if (icc_data_ptr == NULL || icc_data_len == 0)
    ERREXIT(cinfo, JERR_BUFFER_SIZE);
  if (cinfo->global_state < CSTATE_SCANNING)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  /* Calculate the number of markers we'll need, rounding up of course */
  num_markers = icc_data_len / MAX_DATA_BYTES_IN_MARKER;
  if (num_markers * MAX_DATA_BYTES_IN_MARKER != icc_data_len)
    num_markers++;

  while (icc_data_len > 0) {
    /* length of profile to put in this marker */
    length = icc_data_len;
    if (length > MAX_DATA_BYTES_IN_MARKER)
      length = MAX_DATA_BYTES_IN_MARKER;
    icc_data_len -= length;

    /* Write the JPEG marker header (APP2 code and marker length) */
    jpeg_write_m_header(cinfo, ICC_MARKER,
                        (unsigned int)(length + ICC_OVERHEAD_LEN));

    /* Write the marker identifying string "ICC_PROFILE" (null-terminated).  We
     * code it in this less-than-transparent way so that the code works even if
     * the local character set is not ASCII.
     */
    jpeg_write_m_byte(cinfo, 0x49);
    jpeg_write_m_byte(cinfo, 0x43);
    jpeg_write_m_byte(cinfo, 0x43);
    jpeg_write_m_byte(cinfo, 0x5F);
    jpeg_write_m_byte(cinfo, 0x50);
    jpeg_write_m_byte(cinfo, 0x52);
    jpeg_write_m_byte(cinfo, 0x4F);
    jpeg_write_m_byte(cinfo, 0x46);
    jpeg_write_m_byte(cinfo, 0x49);
    jpeg_write_m_byte(cinfo, 0x4C);
    jpeg_write_m_byte(cinfo, 0x45);
    jpeg_write_m_byte(cinfo, 0x0);

    /* Add the sequencing info */
    jpeg_write_m_byte(cinfo, cur_marker);
    jpeg_write_m_byte(cinfo, (int)num_markers);

    /* Add the profile data */
    while (length--) {
      jpeg_write_m_byte(cinfo, *icc_data_ptr);
      icc_data_ptr++;
    }
    cur_marker++;
  }
}