Krita plugins
Krita is quite extensible. You can add new filters, of course, and chunks of user interface like scaling dialogs, and new tools — like weird and wonderful selection tools or a path tool like the one that is right now being worked on for Google’s Summer Of Code. But also new ways for existing tools to paint. I’m working on a Chinese brush simulation based on Clara Chan’s interpretation of Strassman’s Hairy Brushes for Krita 1.6. And finally, you can add complete new colorspaces. We’ve already got various rgb, cmyk and grayscale colorspaces, and also xyz, lab, yuv and lms — but there is no end to the possibilities.
However, the best API is useless without a good tutorial, and I’ve just completed the first draft of Developing Krita Plugins. Apart from extending Krita with C++ plugins (and, if you manage to get automake and gcj to play ball, java), you can use Krita’s document scripting interface to create scripts in python and ruby. And there’s dcop, too, of course, but that’s not as well documented.
So, if you’ve always thought Krita was nothing more than a glorified icon editor, you can now change that. Go ye therefore, and code all kinds of plugins, extending Krita in weird and wonderful ways, in C++ and Java and Python and Ruby.
ps. What I also wanted to say… Krita’s got a pretty good manual, too, in case you just wanted to use this icon editor.