My modifications of the PNGoo batch PNG processor: http://code.google.com/p/pngoo/
Still playing with the project - so far my changes are:
- Multithreading: the GUI no longer is unresponsive while processing, and four files may be processed simultaneously
- Improved GUI: Status text accompanied by a shiny progress bar, and a cancel button
Things I would like to add:
- Entire directory selection (not just this laggy "add files" Windows dialogue) with a recursive option
- Probably more.