Answer
These are steps with Gimp (or any other image processing software) to add a blurred border to an image.
- Select all of the image (Select > All)
- Shrink selection to desired size for paste below (7).
- Feather selection to desired size for paste below (7).
- Copy selection (Edit > Copy) to clipboard
- Scale image to desired output size.
- Blur the scaled image (here I just used a radial blur):
- Paste the image from clipboard:
From the set of G’MIC plugins we also have a preset filter for a simple blurred frame (Frames > Frame [blur]).
In case the background of an image we want to extend is not blurred but has many details we can use the Heal Selection tool to fill the extended areas.
- Crop-Extend source image to desired size:
- Select the extended background to apply heal selection:
- Add blur to hide the artifacts produced by heal selection:
Attribution
Source : Link , Question Author : o_in25 , Answer Author : Community