Are basic image operations lossless for JPEG?

[laurent45654]

I'm thinking for example mirroring, cropping, rotating, etc. Are those operation lossless for JPEG files? If not, is there a way to do lossless operations?

Edit: By the way this is my first post - and I want to thank the developers for their incredible work. This app makes me save so much time managing big image libraries.

[Kadet]

Only rotation can be lossless. In other case, if You do something You have only one option — save image using lossless compression: jxl (Jpeg XL), webp. If You want jpg as saved file, use 100% compression rate (and use jpegli method).

[cday]

I've never used a xnview JPEG lossless operation but thought that there were several, and searching the editor menus have located them currently located in the Metadata tab, surely a strange place for them? You might therefore like to take a look at the several supported options.

You might also like to take a look at this Wiki page, dated 2010 and written for XnView Classic, to see if it adds anything useful, or for further information and background search online.

Regarding saving to JPEG, saving at a quallity value greater than 90% is accepted as resulting in no perceptible gain in image quality, while generally resulting in a substantial increase in file size.

Note:

Surely the Lossless transformations (JPEG) option would be better located in the Edit or Image tab, although I see that making the interface consistent might possibly necessitate moving one or two of those options.

[Kadet]

Regarding saving to JPEG, saving at a quallity value greater than 90% is accepted as resulting in no perceptible gain in image quality, while generally resulting in a substantial increase in file size.

If You don't zoom the image, even 88% quality can look like lossless, but after zooming (300%) You can see jpeg deformation for less than 97% quality settings.

[laurent45654]

>... the editor menus have located them currently located in the Metadata tab

Thanks a lot for this, I completely missed the options were there and it includes lossless horizontal flip too which I often need.