... but if you use gnu don't underestimate this great tool and give it a chance. Imagemagick is very easy to install (in linux at least), script oriented, and very powerful
I have used ImageMagick, and it is very powerful. But its methods and parameters are underdocumented IMO, and there are subtle changes in behaviour between minor versions that make me prefer Imager.
Of course, the external helpers for ImageMagick make it highly convenient when one needs to convert from Postscript (or PDF?) to a raster image. But that's not my use case.