for the scepticism of adding options, everything is said above.
So for now I don’t expect a “quick fix” by the devs because they would have to adapt the core library for that.
well, in fact, there are quite some image improvements done the last weeks or on the way, see Pull requests · chatmail/core · GitHub - all improving within the given constraints, which are similar to eg. telegram, btw.
it seems also be possible to improve rendering of big screenshots as Image optimization - #6 by SWEETGOOD, that should be regarded more as a bug, as the 500k are not used.
EDIT: i created an issue for that at screenshots are sometimes sent in poor quality · Issue #7977 · chatmail/core · GitHub - ftr, it is interesting to browse a bit through the linked issues from the past, there are also lots of screenshots, examples, reasoning