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Is it possible to recover a black & white overprinted document? A hard to get paper accidentally landed in the printer tray and got overprinted with another document. Is it possible to somehow recover the original with layer tricks? No, I cannot reprint the original and no simple way to get a copy.

Technically, I have 2 layers:

  • A + B = scan of the damaged, overprinted document
  • B = scan of the document printed over A

I need to extract A

So, technically I should be able to somehow recover only those black points from the A+B layer, that are black on both layers. I know it is not going to be perfect, but at least I will have the content back. Can someone please help me?

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  • why not simply rewrite the document? your brain and vision is superior to any image processing attempts in such a scenario...
    – Piglet
    Commented Feb 1, 2018 at 13:14

2 Answers 2

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"So, technically I should be able to somehow recover only those black points from the A+B layer" Uh? A white + B black = A+B black, A black + B black = A+B black. In other words, in A+B, you can't tell the origin of all the black pixels that are also black in B. Unless there are minute differences in density between B and A+B, but you would have to provide some samples (and it would require careful scanning, or even taking professional-grade pictures with a good camera since it would likely have more dynamic range than a scanner).

In the meantime, if you want to remove all of B, even if it removes some of A,

  • load A+B
  • load B over it
  • Color>Invert B
  • Set B to "Lighten only" mode
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  • What I meant is a transformation or script that goes trough the canvas, pixel by pixel, like (pseudocode): IF point(x,y) on layer "A+B" = black AND point(x,y) on layer "B" is black THEN set point(x,y) on layer "Recover" to black ELSE set point(x,y) on layer "Recover" to white END IF
    – vilmarci
    Commented Feb 1, 2018 at 14:26
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I know this is an old question, but just in case anyone else needs the answer... I ran into a similar problem, and what I did was the following. In Gimp:

  • File > Open... the combined image (this should appear as a single layer)
  • File > Open as layers... the image printed over the desired document
  • Select the layer containing the second image
  • Layer > Stack > Layer to Top
  • In the Layer panel, right click on top layer > Edit Layer Attributes...
  • Set mode to "Color erase" and click OK

Since we don't have a record of what document A had in each pixel we cannot determine which pixels had content in both document A and B. So, what this technique leaves us with is a clear image of document A with slight gaps where lines from the two documents overlap.

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