I wrote a small introduction of Maemo Image Editor aka libquill. It is designed for image management (thumbnailing, editing, loading etc...) and it provides possibility to extend current set of filters. Image Editor is written in Qt so it provides a nice signal-slot-like interface. All the source code is available in gitorious.

If you feel this subject interesting, please check out the introduction in: http://zchydem.enume.net/?p=23