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• avcodec/codec_internal : add cap for ICC profile support

  28 juin 2022, par Niklas Haas

  avcodec/codec_internal : add cap for ICC profile support
  Codecs that can read/write ICC profiles deserve a special capability so
  
  the common logic in encode.c/decode.c can decide whether or not there
  
  needs to be any special handling for ICC profiles. The motivation here
  
  is to be able to use it to decide whether or not an ICC profile needs to
  
  be generated in the encode path, but it might as well get added to
  
  decoders as well for purely informative reasons.
  It's not entirely clear to me whether the "thp" and "smvjpeg" variants
  
  of "mjpeg" should have this capability set or not, given that the code
  
  technically supports it but I somehow doubt these files may contain
  
  them. In either case, this cap is purely informative for decoders so it
  
  doesn't matter too much either way.
  It's also not entirely clear whether the "amv" encoder should signal ICC
  
  profile support, but again erring on the side of caution, we probably
  
  *shouldn't* be generating (and encoding !) ICC profiles for this type of
  
  media file.
  Signed-off-by : Niklas Haas <git@haasn.dev>
  

  • [DH] libavcodec/codec_internal.h
  • [DH] libavcodec/libjxldec.c
  • [DH] libavcodec/libjxlenc.c
  • [DH] libavcodec/mjpegdec.c
  • [DH] libavcodec/mjpegenc.c
  • [DH] libavcodec/pngdec.c
  • [DH] libavcodec/pngenc.c
  • [DH] libavcodec/tiff.c
  • [DH] libavcodec/webp.c

• fate/png : add test for ICC profile parsing

  28 juillet 2022, par Niklas Haas

  fate/png : add test for ICC profile parsing
  This tests the new "-flags2 icc_profiles" option by making sure the
  
  embedded ICC profile gets correctly detected as sRGB.
  Signed-off-by : Niklas Haas <git@haasn.dev>
  

  • [DH] tests/fate/image.mak
  • [DH] tests/ref/fate/png-icc-parse

• lavfi : add ICC profile support via lcms2

  9 avril 2022, par Niklas Haas

  lavfi : add ICC profile support via lcms2
  This introduces an optional dependency on lcms2 into FFmpeg. lcms2 is a
  
  widely used library for ICC profile handling, which apart from being
  
  used in almost all major image processing programs and video players,
  
  has also been deployed in browsers. As such, it's both widely available
  
  and well-tested.
  Add a few helpers to cover our major use cases. This commit merely
  
  introduces the helpers (and configure check), even though nothing uses
  
  them yet.
  It's worth pointing out that the reason the cmsToneCurves for each
  
  AVCOL_TRC are cached inside the context, is because constructing a
  
  cmsToneCurve requires evaluating the curve at 4096 (by default) grid
  
  points and constructing a LUT. So, we ideally only want to do this once
  
  per curve. This matters for e.g. ff_icc_profile_detect_transfer, which
  
  essentially compares a profile against all of these generated LUTs.
  
  Re-generating the LUTs for every iteration would be unnecessarily
  
  wasteful.
  The same consideration does not apply to e.g. cmsCreate*Profile, which
  
  is a very lightweight operation just involving struct allocation and
  
  setting a few pointers.
  The cutoff value of 0.01 was determined by experimentation. The lowest
  
  "false positive" delta I saw in practice was 0.13, and the largest
  
  "false negative" delta was 0.0008. So a value of 0.01 sits comfortaby
  
  almost exactly in the middle.
  Signed-off-by : Niklas Haas <git@haasn.dev>
  

  • [DH] configure
  • [DH] libavfilter/fflcms2.c
  • [DH] libavfilter/fflcms2.h