ImageMagick

ImageMagick is a command-line image converter. While it does have a GUI display called “Display”, its power shows in three ways:

  1. As a batch conversion application.
  2. It can handle a wide range of image formats.
  3. The newest versions understand color management and use littleCMS, just like Scribus.

ImageMagick is some kind of a black box for image processing, but incredibly powerful when used properly. Versions for Linux, Windows and MacOSX are available.