NConvert is a batch utility for converting graphic files.

It has the features :

Import about 400 graphic file formats
Export about 40 graphic file formats
Multipage TIFF, Animated GIF, Animated ICO support
Resize
Adjust brightness, contrast...
Modify number of colors
Apply filters (blur, average, emboss, ...)
Apply effects (lens, wave, ...)
And many many other things...

NConvert is provided as FREEWARE for private non-commercial or educational use (including non-profit organization)

Note : For commercial use and distribution, it is necessary to register. It is a help for the development of future versions.