iccjpeg.h File Reference

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Functions
DIGIKAM_EXPORT void write_icc_profile	JPP ((j_compress_ptr cinfo, const JOCTET *icc_data_ptr, unsigned int icc_data_len))
DIGIKAM_EXPORT void setup_read_icc_profile	JPP ((j_decompress_ptr cinfo))
DIGIKAM_EXPORT boolean read_icc_profile	JPP ((j_decompress_ptr cinfo, JOCTET **icc_data_ptr, unsigned int *icc_data_len))

Function Documentation

JPP() [1/3]

DIGIKAM_EXPORT void write_icc_profile JPP

(

(j_compress_ptr cinfo, const JOCTET *icc_data_ptr, unsigned int icc_data_len)

)

Notes from Little CMS project (www.littlecms.com)

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.

This code would need surgery to work on 16-bit-int machines with ICC profiles exceeding 64K bytes in size. See iccjpeg.c for details. 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.)

JPP() [2/3]

DIGIKAM_EXPORT void setup_read_icc_profile JPP

(

(j_decompress_ptr cinfo)

)

Reading a JPEG file that may contain an ICC profile requires two steps:

1. After jpeg_create_decompress() but before jpeg_read_header(), call setup_read_icc_profile(). This routine tells the IJG library to save in memory any APP2 markers it may find in the file.
2. After jpeg_read_header(), call read_icc_profile() to find out whether there was a profile and obtain it if so. Prepare for reading an ICC profile

JPP() [3/3]

DIGIKAM_EXPORT boolean read_icc_profile JPP

(

(j_decompress_ptr cinfo, JOCTET **icc_data_ptr, unsigned int *icc_data_len)

)

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.)