Gifsicle

Gifsicle manipulates GIF image files. Depending on command-line options, it can merge several GIFs into a GIF animation; explode an animation into its component frames; change individual frames in an animation; turn interlacing on and off; add transparency; add delays, disposals, and looping to animations; add and remove comments; flip and rotate; optimize animations for space; change images' colormaps; and other things.

Gifview, a companion program, displays GIF images and animations on an X display. It can display multi-frame GIFs either as slideshows, displaying one frame at a time, or as real-time animations.

Gifdiff, another companion program, checks two GIF files for identical visual appearance. This is probably most useful for testing GIF-manipulating software.