Gimp has some hidden secrets - and among them is the ability to generate animated Gifs - so to give it shot I needed to find a couple of sprites - As a Street Fighter fan I obviously selected Cammy White
here and Bison
here.
Before even starting the animation a little work is required on both Sprites file :
1. removing the green color to make it transparent - you need to add an alpha channel on the layer and then using select color / green and remove it - should do the trick.
2. You also need to proceed to a horizontal rotation of Bison's sprite (otherwise the sprite won't face each other)
Now it's time for the big fight "Cammy vs Bison"
From a blank document I started copying and pasting respectively from Cammy Sprites file and Bison sprites file into the new animation layer - when copying make a new layer each time then merge down - so the 2 opponents are on the same layer - the process is quite long and my sequence is 20 layers in total.
The key for a smooth animation is to keep the previous layer visible - so you don't move too far from the previous position.
Each layer will have his own digit for the animation and in parenthesis the duration (100ms) and the mode (replace). This syntax is for Gimp to understand how to manage each layer.
At the end the whole sprites on top of each other looked like this :
To make the whole animation nice - the first and the 20th frame are identical ; it's an imposed trick because the Gif will loop forever - Now to export the result as a Gif file make sure you select "save as animation"
And here's the result :
