XnConvert
Free
XnConvert is a powerful and free cross-platform batch image processor, allowing you to combine over 80 actions.
GraphicsMagick
Open Source
GraphicsMagick is a utility of image processing.
Phatch
Open Source
Phatch (PHoto & bATCH) is a raster graphics editor used to batch process digital graphics and photographs. Phatch can be used on the desktop as a GUI program …
Compare ImageMagick with alternatives
Compare XnConvert and ImageMagick and decide which is most suitable for you.
Compare GraphicsMagick and ImageMagick and decide which is most suitable for you.