[FFmpeg-trac] #9085(undetermined:new): JPEG: YCCK and PhotoYCC support

[FFmpeg]

#9085: JPEG: YCCK and PhotoYCC support
-------------------------------------+-------------------------------------
             Reporter:  Balling      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  pcd, j2k,    |               Blocked By:
  jpeg                               |
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
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 Summary of the bug:

 There are two color spaces that are not supported in JPEG currently, YCCK
 and, as used in Photo CD (see #5923), PhotoYCC. YCCK is (as said in
 https://web.archive.org/web/20170720100717/http://halicery.com/Image/jpeg/JPEGCMYK.html)
 YCC --> CMY and then K is added. Also there is this sample:
 https://bugs.chromium.org/p/chromium/issues/detail?id=1115101 (chromium
 does support it but not icc profiles).
 Implementation: https://github.com/mozilla/mozjpeg/search?q=YCCK
 Note: as said in above link K can be inverted.

 Now with PhotoYCC it is a little more complicated. But I fully described
 it on Wikipedia, fixing the incorrect transfer function (it is the same as
 in xvYCC format that is IN ffmpeg). The matrix is from BT.601 but without
 scaling, so 1.402 (2 * (1 - K_r)) and 1.772 (2 * (1 - K_b)) are not
 applied. Also quantization is different. All is here:
 https://en.wikipedia.org/wiki/Photo_CD#Encoding

 The implementation is also here
 https://github.com/DavidGriffith/finx/blob/17825bf28b2351f96867b34a7dc39f7997e2f9ff/nx-X11/programs/Xserver/XIE/mixie/process/mprgb.c#L1004

 JPEG 2000 also supports both of them (EnumCS 13 and 9).
 This produces very green picture:
 {{{
 % ffplay Channel_digital_image_CMYK_color.jpg
 }}}
 I believe this is a defect, as it is part of the jpeg decoder...
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

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Ticket URL: <https://trac.ffmpeg.org/ticket/9085>
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