There are also some excellent public domain ( i.e. free) tools for manipulating images. ImageMagick is a public domain, X-windows based program for displaying both images and animations (loaded as sequences of images) on a wide variety of platforms. Visit the Web site http://www.imagemagick.org for more information.

One of the most popular, cross platform tools is the GIMP. This tool has nearly the full functionality of Photoshop and can read/write all the image formats EnSight can. It is often installed by default on Linux platforms, but OSX, Windows and other platforms are supported as well: http://www.gimp.org.