Anyone know the one-liner to losslessly recompress an existing JPEG as a JPEG-XL? That was one of the most interesting features of the format to me.
cjxl input.jpg output.jxl
The cjxl --help and cjxl -v -v --help pages are very well done and you'll find the option to explicitly set the option on if you wish to do so.
> Specifically for JPEG files, the default cjxl behavior is to apply lossless recompression and the default djxl behavior is to reconstruct the original JPEG file (when the extension of the output file is .jpg).