This is handy if you are making sprites and you want to create the alternate left or right orientation.
- copy column_flip.py to your ~/.gimp-2.8/plug-ins directory.
- make sure that column_flip.py is marked as executable (sudo chmod +x column_flip.py)
- Go to Image > Transform > Flip Columns...
- Select the number of columns your image has.
- Press OK
- A new layer will be created called flipped...