[KevinH]

Yes, that sounds like a job for a plugin. Lossless algorithms are already used in most png and gif images to some extent. Typically jpeg can have a compression setting and if more needs to be squeezed out, then a lossy compression is done.

But this type of change (ie. batch) is better done in a plugin, I think.

Both the python PIL module and Pyside6/Qt have both lossless and lossy compression routines to make this quite painless. Both can easily be used in a plugin. Perhaps a png file size cutoff filter coupled with an automated jpeg conversion, and a user controllable jpeg lossy parameter inside a plugin to apply to all images would be of interest to others.

I will think about creating such a plugin if others think it would be helpful.