JPEG XL support

[DonaldTsang]

See https://jpeg.org/jpegxl/ since JPEG-XL is coming out in a few months
Also https://google.github.io/brunsli has a sample app
Co-referencing https://ai.google/research/pubs/pub48554
and https://www.iso.org/standard/77977.html

[DonaldTsang]

https://github.com/google/brunsli claims that Python is already supported.

[radarhere]

It does look that way! https://github.com/google/brunsli/blob/master/contrib/py/jxl_library_patches/jxl_pillow.py

[varnav]

JPEG XL format was recently frozen

[DonaldTsang]

@varnav so it has been standarized and passed through, correct?

[varnav]

ISO/IEC DIS 18181-1 is not completely done with being a standard. But this means format will not change anymore. I think it's a good time to start implementing it.

[doublex]

Maybe this code could be used:
https://github.com/cgohlke/imagecodecs/blob/master/imagecodecs/_jpegxl.pyx

[olokelo]

Hello, I wrote a Pillow plugin for Jpeg XL.
It's included in my Python module jxlpy which is based on Christoph Gohlke's project :)
I think it might be useful in this issue.

[doublex]

@olokelo
Great news!

[brunoais]

Hello!
Is there anything missing to move this from the icebox to the backlog?

[aclark4life]

@brunoais Looks like we can now tentatively declare support via @olokelo 's plugin? (Thank you @olokelo !)