Info - Image - Compression: no data

[golemus]

In Browser, info panel - Properties - Image - Compression field there is often missing data (says "None").

So what is (in my opinion) most important function of this field?

Always the more info the better but MOST important would be to know if the image has lossless or lossy compression. There are couple of image formats, most importantly WEBP, JXL, also maybe AVIF/HEIC? that have both lossy and lossless compression options.

According to my very short testing JXL has best lossless compression and WEBP is 2nd.

As JXL still lacks some support I maybe consider WEBP lossless more important for the moment. I intend to convert all PNGs to lossless WEBP as no data will be lost, compression is much better and compability is OK. Then maybe after couple of years i will hopefully convert the WEBP:s to JXL as it feels ultimately better format.

Anyway back to the subject:

- most important for Xnview MP user would be to know if the image content is 1. lossless compression, 2. lossy compression, 3. no compression at all but RAW data.

- most important IMO would be to fix this in following priority order: 1. WEBP, 2/3 JXL/AVIF, 4 HEIC, 5 PDF? (I don't use XNView MP a lot for PDF but noticed that also for it this data field is lacking).

[xnview]

- most important for Xnview MP user would be to know if the image content is 1. lossless compression, 2. lossy compression, 3. no compression at all but RAW data.

It's not possible to know if it's lossy or lossless

[golemus]

It's not possible to know if it's lossy or lossless

I am not sure (yet) how easy it would be for jxl (or avif or heic) but for webp it seems pretty straightforward.

Lossy webp is essentially VP8 (video codec) frame and if you look one in exiftool there is field that says/mentions VP8 but with lossless the field is not there.