How do I enlarge JUST the background layer in GIMP?

Question

I am working on an image with several layers on a green background. I want to make that background bigger WITHOUT also enlarging everything else. How do I do this? Canvas Size doesn't work, it just adds a blank space on one side that I can't fill with the green color. And yes, I selected "Resize layers:none" and "Fill with: Background color." I can't figure out how to fill it with color. Do I just have to start over on a new canvas?

Answer 1

Image>Canvas size lets you pick specific layers for resizing:

you can:

• resize the image-sized layers: this could be a solution for you if the background layer is the only one to have the size of the canvas.
• resize only the visible layers: for a single layer, this means making that layer the only visible one (which is easily done by shift-clicking its eye icon)
• resize the linked layers: click the chain-link icon (next to the eye icon) for the layers that you want to resize.

Note that this operation can clip parts of the initial layer(s) that extend beyond the canvas.