You said that happens with GIFs with transparency, right? I highly doubt he's using GIFs (I highly doubt anyone ever has, does or will use GIFs during their sprite creation). The problem also happens if a point in the sprite is on or close to the edge of the frame such that as soon as it's rotated a couple of degrees the locus of that point will drag it outside of the frame (imagine your sprite is just a big square - what happens when you rotate that square?). So in the first frame it will look fine but in the second frame those points will be clipped and the same points from the first frame will not get "covered up" because the rotated square frame leaves gaps in the corners. Er, hope that made sense.
(edit) Although, choosing not to handle this situation would be a good way to indicate to the user that their sprite will be clipped and they should do something about it
This post has been edited by Guy : 02 August 2007 - 05:12 AM