[edit] I thought I had the originals backed up on CD, it turns out I didn't.
DigiKam and many other programs don't support them natively.
At some point I'm going to have to write a script and convert them all to normal jpegs.
find -type f -name '*.jp2' | parallel --xargs --max-args=1 convert {} {.}.jpgI think some editors now save the original and just store the modification steps (Lightroom does this for raw at least.)
How would that guarantee safe storage, given the previous discussion of all the broken implementations.
1. native JPEG XL lossy compression
2. JPEG lossy compression, but using a more space-efficient storage format than classic JPEG
3. lossless compression
The lossless conversion between JPEG XL and JPEG only works with 2).
Normally you'd only use 2) for existing JPEG images in order to avoid a lossy re-compression, and use 1) for any freshly-created images because native JPEG XL compression will compress the image data even more efficiently than the JPEG compatibility-mode, though if you've got strong interoperability constraints with clients requiring JPEG data you might possibly want to store even newly created images using sub-format 2) in order to get the ability to losslessly convert back and forth between JPEG XL and JPEG.