I use the GAP player when I need to.
Saving to PNG will have layers merged or flattened. That doesn't work for
Saving as GIF is my final result.
To demonstrate the problem I'm having:
In my animation I have two identical frames of an object surrounded by a
transparent background which is represented by small gray squares. If I move
the object slightly in one frame, then play the animation, and detach the
image, then drag the image which is now stepping from one frame to the other to
the desktop screen, the area around the object which has had the object
displaced, shows some of the gray squares each time the image steps to this
displaced image frame.
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