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jcicc.c
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jcicc.c
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/*
* 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++;
}
}