Pull Request resolves #48596.

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

This PR adds initial support for JPEG XL (.jxl) images in Joomla.
Add JPEG XL to the default allowed upload extensions, image extensions and MIME type lists.
Recognise JPEG XL files as images in the Media Manager.
Update the default configuration values in the MySQL and PostgreSQL installation scripts.

More information about JPEG XL https://jpegxl.info/

You can test if your browser supports JPEG XL atv https://jpegxl.info/resources/jpeg-xl-test-page.html You will eithyer see an image or a big red warning that your browser doesnt support JPEG XL

Limitations

Thumbnail generation, cropping and other image manipulation are not supported for JPEG XL files by this change. These capabilities depend on PHP and the underlying image-processing library providing the necessary support, which Joomla must also integrate where appropriate.

This PR enables recognition and upload of JPEG XL files; it does not claim full image-processing support.

Why this is a draft

This PR is a draft and currently targets new installations only. Existing installations retain their saved Media Manager configuration and will require manual configuration changes to enable JPEG XL uploads or maybe an update sql - not sure what is best in this scenario

Testing Instructions

A sample jxl image can be downloaded from https://jpegxl.info/resources/jpeg-xl-test-page.html

Verify JPEG XL uploads on a new installation with MIME checking enabled.
Verify JPEG XL files appear in the appropriate Media Manager filters and media fields.
Verify that browsing the Media Manager does not produce errors when thumbnail generation is unavailable.

Actual result BEFORE applying this Pull Request

jxl images are not supported

Expected result AFTER applying this Pull Request

jxl images can be uploaded and used in the media manager

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed