In GIMP when I want to crop a rectangular image down to a square there’s something frustrating about how the Rectangle Select Tool behaves. Even though I can constrain the proportions of the selection by holding Shift as I drag it out, the selection frustratingly begins outside of the canvas instead of at the border. This defeats the purpose of proportional selection because as you can see below, the selection does not end up being square:
The best solution I’ve found is to enable View > Snap to Canvas Edges and click as close to the edge as possible when beginning the selection. But is there a setting that can be changed to make the selection start at the canvas edges even if you began drawing the selection marquee outside the canvas?
For both rectangle selection and crop tool: use View>Snap to canvas edges, then click sufficiently close to a corner (IIRC 8 pixels or less, by default) and your selection will start exactly on the corner.
Also, once you have a selection, if you release the button and move towards the center of the selection, you get a crossed arrows pointer that says that you can just move the selection by clicking and dragging it. If the Snap to canvas edges option is active the selection will align on the edges if you get sufficiently close.
Source : Link , Question Author : Mentalist , Answer Author : xenoid