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Have fun!

You can combine the two approaches -- some levels adjustment (enough to knock down the background, not so much as to kill text details) with some filtering (by reducing the opacity of the high-pass filtered layer) to make the text more legible. Also try different pixel scales on the high pass filter

So now I have the original image in one layer and the high-pass filtered image in the layer on top of it. Then I set the blending mode of the high-pass filtered image to "divide." This is a lot better, though still not perfect.

I should have mentioned, copy and paste the original image (not the levels adjusted one) into a new layer before doing the high-pass filter, because the output will be a whole layer that has been filtered this way. That's basically a noise image; we want to subtract it from the original.

So we have to go at the noise a different way. One way to do this is using a "high-pass filter." A high-pass filter processes the image, mapping out where pixel-to-pixel variation is high across a certain distance. You tell it a pixel scale to work with. Here I'm trying 3 pixels.

For this particular sample, though, there was a lot of background noise with low pixel values. If I move the slider far enough to erase those, I also start erasing important details in the text.

Always the first thing to try with any scan of a document is to adjust the levels. Usually the text is darker than the page, so if you slide the white slider to the left, you're setting all the pixels lighter than a certain level to white, while the text is still relatively dark.

A fun image processing distraction today -- how to clean up the noisy background of a photo of a microfilm of a medieval manuscript? Thread, in which I use Photoshop, but similar tools are available in GIMP and other image processing software.

Is this better?

Taking a look...

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It depends a lot on the nature of the noise. Post a sample here?

This is actually a scary plausible elevator speech. It’s stupid enough to be true.

You should’ve seen any conference session devoted to either Venus or Europa in the ‘90s…

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Become a full stack engineer for @stsci.edu. 🧪 🔭 #astrocode Must be US citizen or permanent resident. Due Aug 24! apply.workable.com/stsci/j/2194...

imo the ideal Odysseus would've been Gene Wilder, but we would never have deserved that movie.

Blanche would've been a powerful poster