Add JPEG XL Open/Read support via libjxl

[olokelo]

Helps #4247

This PR enables opening and reading JPEG XL images and animations.
Supported image modes are: RGB, RGBA, RGBa, L, LA, La.
A relatively recent libjxl version is needed to compile Pillow with libjxl support.
The main changes are the addition of _jxl.c and JxlImagePlugin.py.
I'm also the author of jxlpy so this PR was influenced by the work of contributors there. This PR is also largely based on WebPImagePlugin.py which had similar implementation.

Why?
JPEG XL has recently seen increased adoption especially in Apple ecosystem. A lot of users are requesting Pillow support for JPEG XL as their products use Pillow and need to be able to handle jxl files.

I'm open to suggestions and comments. I understand such change would need a lot of testing and probably changes. After all Pillow would need to become somewhat dependent on libjxl. Creating documentation will not be a big problem however I decided to wait for feedback from Pillow core developers.

[brunoais]

May you please commit the images as LFS?

[olokelo]

Do you mean those .jxl files under Tests/images I've committed? I'm not really sure how to do that.

[brunoais]

The explanation is outlined here: https://docs.github.com/en/repositories/working-with-files/managing-large-files/configuring-git-large-file-storage
Nevermind. I just noticed they are not putting the test images as lfs:

They already setup lfs and they only use for other larger stuff. Let it stay as you did.

[olokelo]

Mac OS builds were failing because clang complained about goto labels being declared before variables in scope.
I also merged @radarhere's commits that remove the jxl feature which was causing troubles before.
Now it should be fine. Almost all checks pass except codecov.

[hugovk]

I've merged in main to include #7827 to fix a lot of the warnings I'm seeing on macOS 14.4 Sonoma with CommandLineTools installed.

And this is failing to build for me with:

      src/_jxl.c:174:12: error: incompatible integer to pointer conversion returning 'int' from a function with result type 'void *' [-Wint-conversion]
          return true;
                 ^~~~
      /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/15.0.0/include/stdbool.h:21:14: note: expanded from macro 'true'
      #define true 1
                   ^

Full log: log2.txt

[olokelo]

I've merged in main to include #7827 to fix a lot of the warnings I'm seeing on macOS 14.4 Sonoma with CommandLineTools installed.

And this is failing to build for me with:

      src/_jxl.c:174:12: error: incompatible integer to pointer conversion returning 'int' from a function with result type 'void *' [-Wint-conversion]
          return true;
                 ^~~~
      /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/15.0.0/include/stdbool.h:21:14: note: expanded from macro 'true'
      #define true 1
                   ^

Full log: log2.txt

Thanks for reporting. The _jxl_decoder_count_frames function was declared to return void * instead of bool. That was an obvious mistake and I'm even not sure why it worked under gcc.

[hyperion4]

@radarhere is there any movement on this PR?

Currently a Rust version of the libjxl library is being implemented and looks like it's going to end up in Firefox, and Adobe is planning on adding support for JXL for PDFs as well (see the this interop discussion)

Not only that, Google seems now to "consider" to add JXL back to Chrome.

https://groups.google.com/a/chromium.org/g/blink-dev/c/WjCKcBw219k/m/NmOyvMCCBAAJ

They will add it, they just try to save face right now by talking nonsense about now seeing "developer signals".
With Apple and now Adobe also supporting it they have no choice anymore and we all know why they tried to bury JXL.
I hope JXL to be added to PIL as soon as possible.

[radarhere]

1. Will this decoding allow us to decode float32 JXL images? This is important for us as JXL files are great for scientific data (depth, thermal, etc)

@j99ca if you have any sample float32 JXL image that we can distribute as part of our test suite under the Pillow license, that would be helpful. Ideally, with an attached version in another format so that we know if we have read it correctly

[radarhere]

I've created libjxl/libjxl#4548 with my latest problem in this PR, if anyone here has wisdom to offer.