Ok... Just a thought here for something I think should exist... Perhaps it does already...
Is there any way to "tell" Photoshop « Don't compress to heavily in this particular area of the picture [Because that's where the bird/person/cat/whatever is]. The rest, where there's just shrubs, sky, grass, etc, you can compress more to save space. »
I'm thinking such a function would be useful, especially for posting pictures on the web, when you want small files but you don't want your main subject to have compression artefacts.
Does it already exist?