Created attachment 175868 [details]
Example screenshot, which can't be opened with gwenview.

SUMMARY
Opening some (not all) old screenshots of various resolution (converted to .jxl in q4 2023) results in "Loading image failed." message. 
Those screenshots that fail to open in gwenview, are able to be displayed properly in ristretto.
STEPS TO REPRODUCE
1. Aquire .jxl file lossly converted with imagemagick (version possibly from 2023-10 to 2023-12), and later possibly modified with "file optimizer" software
2. Observe that the file has a proper thumbnail in dolphin
3. Open said file
4. Observe result

OBSERVED RESULT
Gwenview opens, but instead of showing the screenshot it shows
"Loading 'Zrzut ekranu 2023-02-7 o 12.03.33.jxl' failed
Loading image failed."

EXPECTED RESULT
Gwenview opens, and shows the screenshot.

SOFTWARE/OS VERSIONS (from kinfo)
Operating System: Fedora Linux 41
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.11.7-300.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5700X 8-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 7700 XT


ADDITIONAL INFORMATION
Package "libjxl-1:0.10.3-5.fc41.x86_64" is already installed.
Package "kf6-kimageformats-6.8.0-1.fc41.x86_64" is already installed.
Package "qt6-qtimageformats-6.8.0-1.fc41.x86_64" is already installed.
Issue also existed on cachyOS (Arch-derivative distro).