Xenomorph is OpenSource software running on Unix/X11 systems. It provides a
unified concept of polynomial and morphologic image filters. It is built for
precision, not for speed, that means it works in floating-point mode
internally.

It can read PNG, JPG and many other formats, and it writes PNG. A nice feature
of this software is it's upgradeability by adding new filters.

WWW: http://xenomorph.sourceforge.net/