by Karlis » Wed Jul 29, 2009 9:33 pm
Hm, actually there is no feature that would do this in the GIF animator (although this is a good idea and probably we should add it). What you can do is to copy the frames one by one, paste them in a graphics editing program e.g. MS Paint and then copy back.
Or, even easier, use Frame -> Edit Frame... and follow instructions. Once MS paint is open, use Image -> Flip...
This is feasible only if you have no more than 3 - 5 frames, for larger amount it would be pain, I believe.