If I don't know the aspect ratio of an image, what is the most efficient method to set the selection aspect ratio to that of the image? The fastest I've found (not fast at all) is to look at the window title and enter the full image dimensions in the aspect ratio text box (e.g., 4752:3168).

For reference, the Digikam image editor has this functionality as a simple drop box entry in the cropping tool:

Digikam crop settings


The fastest way I can think of:

  1. Select your selection tool (rectangle select or circle select)
    It isn't necessary to do this first, but it's necessary for step two.

  2. CtrlA to select all

  3. Enable Fixed in the selection tool options:

    enter image description here

  4. Click on the selection to make the scaling handles appear, and scale the selection

  • 3
    Thanks, this helped me out. To clarify for others: if you make the selection first, the "current" in the Fixed box refers to that selection. You can also enter a custom value in the form x:y. For instance you could use 2:1. Any further resizing of the selection box will be locked to your custom value. – Usagi Oct 6 '16 at 17:51
  • How do you access the "selection tool options" ? – kris Jul 8 '19 at 13:14
  • @kris normally they are in a panel below the tool icons, but if it was undocked somehow you may have to re-show them with window > dockable dialogs (iirc, on mobile atm) – gandalf3 Jul 8 '19 at 17:24
  • I couldn't for the life of me find it - but I did find that I can use Shift + S to scale, and then there is a little link to click to maintain the aspect ratio. I'm a noob to GIMP. – kris Jul 9 '19 at 1:15
  • @kris That's even better, glad you got it sorted out. In case it's still useful, the proper location for re-showing the tool options dialog is Windows > Dockable Dialogs > Tool Options. I think it should be here by default though, as long as you have a tool selected. – gandalf3 Jul 9 '19 at 8:36

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