python-pillow
Some unpackers are misnamed
RGB15 actually reads data as XBGR (XBBBBBGGGGGRRRRR).
https://github.com/python-pillow/Pillow/blob/a8f434f67657d9286bafb0f132ac608276fa96c0/src/libImaging/Unpack.c#L661-L674
RGBA15 actually reads data as ABGR (ABBBBBGGGGGRRRRR).
https://github.com/python-pillow/Pillow/blob/a8f434f67657d9286bafb0f132ac608276fa96c0/src/libImaging/Unpack.c#L676-L689
RGBA4B actually reads data as ABGR (AAAABBBBGGGGRRRR).
https://github.com/python-pillow/Pillow/blob/a8f434f67657d9286bafb0f132ac608276fa96c0/src/libImaging/Unpack.c#L766-L779
etc.
Basically, all of the unpackers that read less than 8 bits per band appear to be backwards.
This is related to #8019, because I wrote those packers in the correct order, which is actually the opposite of the unpackers.
Here's the names they should be based on what they actually do and the format specified in Unpack.c.
https://github.com/python-pillow/Pillow/blob/824db7152d1159bf3a895e7699b16ebc77298e77/src/libImaging/Unpack.c#L1534-L1543
RGB;15 → XBGR;1555 RGB;16 → BGR;565 BGR;5 → XRGB;1555 BGR;15 → XRGB;1555 BGR;16 → RGB;565 RGB;4B → XBGR;4 RGBA;4B → ABGR;4 RGBA;15 → ARGB;1555 BGRA;15 → ABGR;1555
Unfortunately the specified format doesn't quite work because the bands in these modes aren't all the same size, so I just listed all of the sizes for those modes.
The good thing about listing out the band sizes though is that those names aren't already being used, so I could add all of them as "new" rawmodes and the old ones could be deprecated without interfering with one another.
There's a slightly awkward overlap in code that would change with this and with #7965.
