.ani Animation File

The .ani file is basically a series of SDL_image-compatible image files (usually PNG) appended together in one file. It is organized into a header for the .ani file as a whole and a series of frames, where each frame is a filesize, followed by a file itself (e.g. a PNG file). The header is 3 bytes long and the frames are 4 bytes + the size of the image file long (e.g. so each frame is likely a different size, unless every frame is made up of the exact same image, but then that wouldn't really be an animation, would it?). 

Byte #1 = 1 (represents version, signed)
Byte #2 = Number of frames (signed, must be less than 128)
Byte #3 = Frame Delay (signed, must be less than 128, in milliseconds, e.g. 125)

Frames

Repeat for i=0,number of frames:
4 bytes = 32-bit signed long, image file size
N bytes = the image file (e.g. a PNG file) itself, where N is the 4 byte signed long we just read