Announcing PhotoDemon: A Fast, Free, Open-Source Photo Editor and Image Processor.
Tanner Helland spent 12 years working on an advanced image processing program. (Think PhotoShop, but without any on-canvas painting tools.) The software is now available under the title “PhotoDemon.” It is fast, free, completely open-source (BSD licensed), and it provides a number of useful features, including macro recording and automated batch conversion.
If you're looking for a lightning-speed batch image processor, PhotoDemon is the program for you. If you're interested in app development, it also has some interesting history that's worth reading.