Send selection to new image in GIMP

Question

I am trying to create a machine learning plug-in to help with the creation of training data. I find that GIMPs selection tools are so easy, simple and quick to use, therefore is there a way to export a selected region to a different image of the same size in the same position and then to block colour it? (this will be done procedurally, however I am not sure how to even do this through the GIMP interface) any help appreciated.

Answer 1

If the target image exists (with the same size)

• Create a selection in source image
• Save to channel (Select ➤ Save to Channel)
• Open the Channels list
• Drag the thumbnail of the saved selection to the canvas of the target image where it will become a layer (white selection on black background)

If the target image doesn't exist yet

• Create a selection in the source image
• Save to channel (Select ➤ Save to Channel)
• Open the Channels list
• Click the saved selection channel (this makes it the active "drawable"(*))
• Select ➤ All (Ctrl-A)
• Edit ➤ Copy (Ctrl-C)
• Edit ➤ Paste as ➤ new image (Ctrl-Shift-V). This creates a grayscale image.

Note: there is no one-to-one mapping between UI operations and the API, but the API can be simpler and you can likely duplicate the selection mask to a "drawable" in the other image, but this matter is better handled on StackOverflow.

(*) a "drawable" is an object on which you can alter pixels: layer, layer mask, or channel.

Answer 2

1. Make a selection of something
2. Edit > Copy
3. Image > Duplicate
4. Click on the tab for the new document
5. Delete the existing image layer in the layers panel
6. Edit > Paste in Place
7. Select > None
8. Choose a new foreground colour
9. Engage the alpha lock (in the layers panel)
10. Edit > Fill with FG colour