I think what you should look for are transitions. Seem to remember dedicated scripts for this. I will have a look around.
This one came from the gmic Gimp plugin, but it involved a bit of fiddling around as far as direction is concerned. Not really suitable for batch operations.
This one came from the gmic Gimp plugin, but it involved a bit of fiddling around as far as direction is concerned. Not really suitable for batch operations.