This function is currently not documented; only the argument list is available.
This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function at your own risk.
Compares each image the GIF disposed forms of the previous image in the sequence. From this it attempts to select the smallest cropped image to replace each frame, while preserving the results of the animation.