The opposite of dust and scratches! How to preserve fine lines?

[Starbase1]

I'm currently working on cleaning up some old archive images, that are very poor quality, (I attach an example).

What I want is to preserve the lines in the diagram, clean-up breaks in them, and lose the grey blotches in the background.

It occurred to me that this is basically the opposite of a dust and scratches filter, i.e. I want to keep the fine lines!

The obvious first step was levels, but darkening the lines made the blotches more visible. So, is there a select option that will allow me to select the sharp dark elements, like I would if I was selecting scratches? That would seem to be an excellent starting point...

Thanks,
Nick

 

 

[Pšenda]

You can also try vectorization.

For example vectorizer.ai
F213_O5-1_D230_L113-ThelastversionoftheLOK.png.b91465ab99e8f8da68f1c4b846fe9b89.svg

Edited July 17, 2023 by Pšenda

[Starbase1]

Very interesting! That's a lot better than the last time I looked at conversion to a vector format.

I'd still like to know how to do the selection though.

 

Thanks, Nick

[GarryP]

I managed to get the attached image by using the Flood Select Tool with 69% Tolerance and Contiguous set to OFF, selecting a black pixel.
It’s not ‘perfect’ but it’s a bit cleaner and might be a better starting point for later processing.

I think the important question is: How, exactly, do you define “the sharp dark elements”? Specifically, how “sharp” and how “dark”?

 

[Return]

Erase whitepaper filter and mask out or erase the dust parts.
or
Blend range the white and mask out or erase the dust parts.

[v_kyr]

1 hour ago, Starbase1 said:

That's a lot better than the last time I looked at conversion to a vector format.

Well it's pretty much the same as before here ...

 

And always keep in mind, that the results of any bitmap-to-vectors tracings do highly depend also on the overall quality & size of an input bitmap/pixel image. So the better (less noise, less unwanted shadow regions/scratches/dust, the more clear visable lines, the more clearly distinguishable pixel colors and shades, good contrast & sharpness ...) an image/drawing has/is, the better will be the final vectorization result. - Thus bad images/drawings have to been preworked accordingly, in order to yield and get good vector results.

[Starbase1]

GarryP, thanks for that - you have hit the nail on the head with the question!
This is why I was thinking of the kind of controls you get in the dust and scratches.

It's a 50 year old document on cheap paper that someone pointed a low res phone camera at from what I can work out!

Not the best source quality...

Nick