Lossless transformations for JpegXL

[nji9]

AFAIK the reference implementation of JXL since long supports lossless transformations.
(Some as simple Metadata entries).
It would be nice to have it available in XnViewMP.

[WinnieW]

The only lossless transformations for JPEG XL are rotating the image, other transformations are much more complicated to implement,
because JPEG XL is much more complex as format compared to traditional JPEG.

[nji9]

What's your statement based upon?

AFAIK cjxl already supports rotation, flip h/w and make progressive.

[WinnieW]

Besides from lossless JPEG recompression, cjxl always reencodes images, and the result is only lossless when lossless compression mode is used.
For already existing lossy JXL images there are no lossless transformations in cjxl, right now.