Document JPEG 2000 support for writing YCbCr and reading subsampled color #7636
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nulano
reviewed
Dec 26, 2023
…olor Read support for subsampled RGB and YCbCr color channels was added in 4f4c3b3 and not documented at the time. Write support for YCbCr appears to date to 61fb89e, the original commit. Retain the existing language about YCbCr input conversion to RGB, even though it's not completely correct. OpenJPEG through 2.5.0 doesn't set color_space in opj_read_header(), so we end up in our OPJ_CLRSPC_UNSPECIFIED fallback path, which guesses sRGB if there's no component subsampling. This means we currently can't round-trip YCbCr via JPEG 2000. The next OpenJPEG release will fix this, so leave the docs as is. Also fix typo: .j2p -> .jp2.
nulano
approved these changes
Dec 27, 2023
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Thanks for your thoughts @nulano |
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Read support for subsampled RGB and YCbCr color channels was added in 4f4c3b3 and not documented at the time. Write support for YCbCr appears to date to 61fb89e, the original commit.
Retain the existing language about YCbCr input conversion to RGB, even though it's not completely correct. OpenJPEG through 2.5.0 doesn't set
color_spaceinopj_read_header(), so we end up in ourOPJ_CLRSPC_UNSPECIFIEDfallback path, which guesses sRGB if there's no component subsampling. This means we currently can't round-trip YCbCr via JPEG 2000. The next OpenJPEG release will fix this (uclouvain/openjpeg#1463) so leave the docs as is.Also fix typo:
.j2p->.jp2.