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removing fold shadow / highlight from a scan
Hi guys. I am new to GIMP. Today I was trying to balance the background of a scanned audio CD cover that had slightly different color tones (highlighted) on a folded side of a scan. Pretty much something like this issue presented on this scanned page:

What I used was the Select by color tool and then filled the area with Bucket fill tool with just one of the colours from the rest of the background using Color picker tool to sort of balance the overall background to get rid of that fold.

But I am wondering if you could actually fill the area with a portion of an image itself (something like cloning / healing). I can't see this option in Bucket fill tool. The reason is that I think it might look better being filled with actual scanned pattern rather than one strick colour all over.

Or is there a better way to get rid of fold shadows / highlights?

Thank you very much for your answers.
For that particular type of scan the method proposed by Ofnuts works very well.

Duplicate the layer
Put the duplicated layer mode to divide
Blur the duplicated layer, 'Filters -> Blur -> Gaussian Blur'
Adjust the x/y values and being a GEGL filter you can see the result as you adjust.


Otherwise, the gmic plugin has a very good 'repair scanned documents filter.
Another technique (better done in Gimp 2.10):
  • Duplicate the layer, and set the top layer to Grain extract: the whole image turns a uniform gray.
  • Filters>Blur>Gaussian blur and blur the top layer. The characters will re-appear in black. Increase the blur until the characters are dark and the halo around them is no longer visible but don't go too far otherwise the fold shadow will reappear.
  • Layer>New from visible and use Levels or Curves to make the grey white, and the black very black

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