Hello!
There is already post here about AzPainter software but there is no any good description of it and BTW I compiled the latest version and made .sfs to try it out without installation. Why it is interesting?
First of all, it is Photoshop like program. It has many of its common tools and features: layers, brushes, curves, selections, filters etc.
Second, it doesn't use any GTK/Qt toolkit at all.
Third, it can open PSD files along with jpg/png etc. I've checked some PSD. Looks like it really opens them but not the latest ones.
At last, it is just 550Kb in a size So you probably should check it out because of that at least
What I've got the developer is a woman from Japan with a nickname Azel. Thats why its called AzPainter.
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It is 64bit and I checked it on Bionic and Fossa pups but in the link above on the older post you may find 32bit version that flawlessly runs on Tahr in a milliseconds.