Initial JPEG XL decoder

[kmilos]

Refs. #516

This is just a basic POC, largely based around the darktable imageio_jxl reader.

[github-actions]

The proposed diff is not clang-formatted.
To make this check pass, download the following patch
(via browser, you must be logged-in in order for this URL to work),
(NOTE: save it into the repo checkout dir for the snippet to work)
https://github.com/darktable-org/rawspeed/actions/runs/15758629170/artifacts/3363237698
... and run:

cd <path/to/repo/checkout> # NOTE: use your own path here
unzip clang-format.patch.zip
git stash # Temporairly stash away any preexisting diff
git apply clang-format.patch # Apply the diff
git add -u # Stage changed files
git commit -m "Applying clang-format" # Commit the patch
git push
git stash pop # Unstast preexisting diff
rm clang-format.patch.zip clang-format.patch

[schwittlick]

Anything we can do to move this forward?

[0fbcb238c0]

LibRaw 0.22 released with support for compiling with Adobe's DNG SDK. Are there plans to use it for decoding 1.7 DNGs with JXL?

[kmilos]

Anything we can do to move this forward?

There has been zero feedback on this PR so far.

Are there plans

No such plans here.

In any case, I'm personally not intending to keep working on this given the current circumstances. Anyone should feel free to pick up this POC and run with it.