Comment by adgjlsfhk1

See https://devtalk.blender.org/t/jpeg-xl-as-an-intermediate-for.... TLDR is that one of the really interesting things JPEG-XL adds is the ability to have an arbitrary number of non-color channels. The current solution is generally to use separate grayscale images for each extra thing you want to store, which is inefficient since it loses the ability to compress the correlation between the separate channels. Another example usecase would be capturing images at 10 different wavelengths rather than the typical RGB.