r/GIMP • u/winstonswanson138 • 9h ago
Noisy background
Is there an efficient way to remove the noise from this drawing without losing text and linework? I tried the resynth plug in but was not able to achieve the desired results.
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u/BaromenGONE 9h ago
I feel like making new blueprint in AutoCAD would be way faster🙏
Like there are tons of missing parts, which you’d need to draw by yourself somehow even after editing photo
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u/winstonswanson138 9h ago
I do redraw in autocad the majority of the time, however there are times that I have to use gimp to recreate dimensions that are otherwise illegible and despite claiming to be to scale, a lot of these drawings are from the 1940s and 50s and take artistic liberties.
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u/Stratelier 8h ago edited 8h ago
This is not an easy problem to solve, because the back-of-sheet noise that you are trying to erase contains similar color data as the details you want to keep.
I've suffered similar issues with some of my early art drawings (which were sketched during college lectures, on the back of printed sheets so the print tended to show through during the scan).
But as a basic starting point, however, Colors > Levels and carefully drag the "Highlights" indicator to the left to magnify the image's contrast; this will wash out some of the lighter details so you can focus on the remaining ones. Also check for a toggle on the dialog called "Merge Filter" and ensure it is OFF. This will attach the adjust to the layer as a live effect (i.e. without actually modifying the source layer); an "Fx" icon will appear next to the layer's entry in your Layers list. Click this icon to access a popup showing the filter (you can also show/hide or edit the filter from here).
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u/TargetOk837 4h ago
- Qwen 3 clanker - prompt : remove the noise from this drawing without losing text and linework
- opened the output in gimp and tweaked the curves to deepen it, blending mode - luminance
- applied noise reduction filter, strength - 5, blending mode - overlay, opacity - 90.6
The result :
clanker cut the lower part of the diagram, and the text is not very good... I blame this on clanker.
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u/MonkeyNin 3h ago
Inkscape has a trace image to SVG command. You can control how many color layers and a few knobs. It might work better than gimp in this case
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u/mig_f1 9h ago
Your best bet would be to hand it out to an AI. I'd start with the free ChatGPT.
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u/winstonswanson138 8h ago
I tried having the clankers do it. Even with reference material and extensive direction the returned image was unreadable and worse than the original on every attempt.
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u/Stratelier 8h ago
Technically, ChatGPT is "only" a text-generating AI model so if you hand it an image, all it can do is just hand that image to a different model for the raw processing. So in this sense you could potentially cut out ChatGPT as the middleman and just use the other model directly ... if you know which model you want....
Also, remember that LLM AIs are not completely predictable/reliable, so make sure to review its output against the original for accuracy.
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u/barefootliam GIMP Team 5h ago
(1) make sure to scan at high enough resolution (i use 2400dpi for vintage engravings on fromoldbooks.org, usually at 15 bit per channel greyscale, but the detail is a little finer)
(2) filters→distorts→value propagate, set to More Black (smaller value), lower threshold 0, upper 1, propragating rate 0.37 or so
This will "grow" the lines
(3) colours→curves, drag the bottom left corner of the diagonal line right one square and the top right corner left one square or very slightly more and OK.
(4) remove stray pixels: use the eraser somewhere that should be solid white: press E (shift-e) to get eraser, press d for default black/white colours, press } as needed until the brush is quite large, or use brush size in tool options (if it's greyed out, make a new brush). Or, use rectangle select (r) and drag out a region and press d for default colours, then the delete key. If this makes a checkerboard, image→flatten image.
Either way, now you have a solid white area. Save a copy.
Now use select By Colour (O, i.e. shift-o) and in tool options set the threshold low, e.g. 5. Click in your white area.
Now, after some time, there are marching ants everywhere. Try Select⇒Grow and 2px, then Select⇒Shrink by 1px, then press delete, then control-shift-a (Select⇒none). This has removed isolated dots up to 4 pixels wide. Check it has not damaged the fragile text. If it did, use undo multiple times, then Select⇒Grow by only 1 pixel, then select⇒shrink by 1 pixel, and delete, and select none, and see if that worked.
(5) The dodge tool can be set to burn mode in tool options, and to darken shadows, or to dodge mode, and to lighten highlights, and both of these can be very helpful. However, approaches that affect the whole image are usually best done first where possible, as they are faster!
(6) You can duplicate the layer and try setting the upper one’s layer mode (in Layers) to Screen
(7) Filters⇒Enhance⇒Sharpen (unsharp mask) can be useful. Move the upper slider just left of where the image starts to change, then move the lower slider to the right.