is brilliant! If you want to do something to an image, Imagemagick can do it!
Works on Linux and Windows.
Can be scripted.
Just use Imagemagick for your image manipulation needs.
Advert over. The following posts will serve as a reference for me, but also to show what imagemagick can do. Other than one liners, there will likely also be some bash scripting. I have also littered these posts with links to the IM documentation for all the features available with each of the actions.