Shrink Image Files With GraphicsMagick
GraphicsMagick is a fork of the ImageMagick project that describes itself as “the swiss army knife of image processing”. It contains command-line utilities for converting from one image format to another with the option to resize images. This makes it perfect for routine jobs that don’t require a GIMP or Photoshop-like GUI, like creating compressed copies of original images for display on a web site. Chances are, you already have GraphicsMagick installed with your distribution.