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Howdy all,
I'm going to start fiddling with the best way to scan in and clean up aperture cards to make them as readable as possible. Has anyone solved this problem before? I expect the process would be similar for microfilm and microfiche if anyone has worked with those.
As I sort out best practices I will share my findings here.
Thanks,
-Kirby
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There are many ways to tackle this. I have listed 4, but I'm sure others will come up with more ways.
1. Contrast (about 40)
2. Levels (right hand white triangle to about 220)
3. Threshold (black triangle to about 190)
4. G'MIC : Repair > Repair scanned document
I also suspect that there will not be a single best method that applies to all images.
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04-23-2018, 06:54 AM
(This post was last modified: 04-23-2018, 07:01 AM by Ofnuts.)
A good way to normalize the lighting of the image:
* Duplicate the layer
* Apply a very heavy gaussian blur. The drawoing should no longer be visible (I use something like 1/5th of the image diagonal)
* Put the top layer in Grain Extract mode.
This is more or less computing a 128-centered difference between the layer and a blurred copy of it. Then you can use Curves with mess impact on the fine detail.
Edit: some success with a different method, use the Wavelet decmpose plugin and decompose to 7 levels, then keep on the Level 4 and the residual. But time to go to work...