Proposals made so far were based in the increase of canvas size until the final dimensions and aspect ratio were achieved, with more or less color effects.
However, we have another possibility: to work "inwards"...
Work with layers
To do so, we will need three different layers: a duplicate of the background picture and another, empty layer between those two identical ones.
Both layers can be created from the context menu that appears when clicking on a miniature in the layers' window, selecting "Duplicate layer..." or "New layer...", respectively.
It is important to have the empty layer among the other two.
With the upper layer active, select the whole image (Ctrl + A). Then, reduce the selection (Command "Selection - shrink") as per your preferences. I will keep the 40 pixels (5%) from previous examples.
Now, remove the contents in that selection, by presing "Supr" key. In principle, you should not see any difference, for you have an exact copy in the background. However, you should see the result in the miniatures of the layers' window.
Without unselecting (keep the selection active...), move to the mid empty layer, and fill it with white (or black...).
Now, shrink the selection again, I choose a 2% (16 pixels) and delete the white content ("Supr" again). You should see the bottom layer now.
In order to save this design as JPG, you need to merge all information in the same layer. You can do this by selecting the option "Flatten image" from the context menu from the layers' window, when clicking on a miniature with the right button.
This process can be quite effective when a color image is combined with its black-and-white version.
It is important that the original image includes much information on the surrounding areas that will end up making the frame.
For this last reason, it is also good to leave some "air" around the subjects when taking the picture, if you know that you will be applying this effect...
You might also like...
- Advanced frames with GIMP (I)
- Basic framing with GIMP
- Traditional colouring with GIMP
- Traditional B&W colouring with GIMP
- Fake HDR with GIMP
- B&W photos colouring with "multiply" in GIMP
- Further GIMP posts...