Each frame of the "Galloping Buffalo" film from the 1860's was rendered in Adobe Illustrator, and color-coded to determine the amount of change that occurs in both the top of the body and the legs.

By simplifying the frames (below), it may be possible to keep the top of the body "constant" and relying on only the legs to represent the motion. To animate the potential, each frame was clipped in PhotoShop and opened in GIMP with an image on each of 15 layers.

Then, the layers were exported as a GIF, with the button "Save as Animation" clicked. You can modify the speed of the resulting animation and the file size.