I'm using GIMP to label data in an image, for a machine learning application. I simply want to divide the image into five colors, and I'm using the selection tool (Scissors Select) to outline the various regions. My question is, if I outline one region, and paint it red, how can I use the top border of this previously selected region to be the bottom border of a new region? (Let's say I will paint this new region blue.)
- with the Red selection still there:
Select>Save to channel
- make a selection for Blue, with some overlap with Red
- open the Channels list, right click the saved selection, and choose
Subtract from selection. This will remove from your current Blue selection the bit that was in the Red selection.