Restoring old blueprints using GIMP

I'm sure many people will find it useful! Not everyone uses GIMP but I believe the general principles apply from one software to the next.
 
Yes and no.


There are specific filters from the GMIC plugins set which are very useful. You may find something similar in another program, but it may got get the same results. I actually find GIMP better than Photoshop for this specific task. Best of all GIMP is free, so there's no cost or risk to trying it.


Will post the tutorial tonight (I will do screencaps on a Windows PC for ease of understanding).
 
GIMP is lovely and very useful if you want full-blown Pro Photoshop style tools, but just thought I'd recommend Paint.NET too:


http://www.getpaint.net/


I find it much more user friendly and intuitive (and I'm hardly a spring chicken on PCs) and that it still does every last thing I could ever want - the main difference seems to be that GIMP is written for those who already know Photoshop inside out whereas Paint.NET is more welcoming to us idiots :D


Having said that, I look forward to your tips ;)
 
So, this particular scan isn't bad, but you wouldn't want to use it in a book as it is. We want a high contrast black and white drawing for maximum legibility.


Step 2 - change to Greyscale. - Image - Mode - Greyscale.
 

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The next step is to sharpen up the lines of the drawing.


Go to Filters - GMIC


In the window which pops up double click on Enhancement and then select "Octave Sharpening".


You can then play with the parameters to get the nicest sharp lines you can without affecting the whole picture. I left everything on default except "threshold", this is the level at which your sharpen affects the picture. Threshold 0 is sharpen everything in the picture - by slowly increasing the value of threshold you can see the areas of flat colour becoming less affected, while the sharp lines stay sharp. I've selected 15 in this screenshot, but I actually found that leaving this at 0 is fine, as the next filter will remove any noise you add to the background - you should concentrate on getting every line sharp here.
 

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So - our lines are pretty sharp, but there are big blocks of grey in stripes down our blueprint. What to do?


Go back into GMIC, Enhancement, and select "Bilateral filtering".


This plugin effectively smooths out the noise in the image without affecting the sharp lines. I left settings at default and then moved "Value" slider to the right until the gray splodges were smoothed out nicely.
 

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So, last operation - get rid of most of the grey bits and increase contrast further.


Go to Colours menu - Curves


You want to drag the bottom left point rightwards to darken the dark bits of the image, and the top right point leftwards to lighten the light parts of the image. As we've made our grey noise relatively light, it should almost completely vanish. There is always a tradeoff here where you may lose bits of the image you want - here I dragged the middle across a little which seemed the best compromise. There's still a tiny bit of noise present, but this can be simply removed with the eraser tool if needed.
 

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And here's a version using GMIC fourier transform filters plus the above techniques. Probably the best version.


Of course, these work best on the original scan, but even relatively low res scans can be edited with this technique.
 

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Now try this extremely challenging blueprint scan by Bill S. I have added my previous attempt in 2009 as a benchmark.
 

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As my submissions have made me the poster boy of what not to do. B)

I don't come across as a total idiot, (partial is true), a number of the rolls of microfilm
that I have viewed are very dark, almost black as the original scan shows.
However, dark or not I am going to grab the scan as I have not found that info anywhere else. :)

With that said, I am off to try some of these tips as I have plenty of other samples to work on.

Thanks overscan for the tutorials!

bill

overscan said:
Now try this extremely challenging blueprint scan by Bill S. I have added my previous attempt in 2009 as a benchmark.
Click to expand...
 
Thank you for this! I have GIMP on my netbook, (posting from my work computer now) and I have tried to clean up some images in the past and had little success. With these tips, I'm certain I will get better results.
 
Bill S said:
As my submissions have made me the poster boy of what not to do. B)

I don't come across as a total idiot, (partial is true), a number of the rolls of microfilm
that I have viewed are very dark, almost black as the original scan shows.
However, dark or not I am going to grab the scan as I have not found that info anywhere else. :)

With that said, I am off to try some of these tips as I have plenty of other samples to work on.

Thanks overscan for the tutorials!

bill

overscan said:
Now try this extremely challenging blueprint scan by Bill S. I have added my previous attempt in 2009 as a benchmark.
Click to expand...
Click to expand...
I didn't mean to imply it was your fault Bill - I'm aware how challenging the source material is, this just so happens to be one of the most hard to fix images I've seen.


I will add some more tutorials - this isn't in any way the only way to accomplish this task, just one way.
 
overscan said:
I will add some more tutorials - this isn't in any way the only way to accomplish this task, just one way.
Click to expand...

Seems like a very well thought out, streamlined process. Pushing above and beyond that quality is surely an effort in diminishing returns. Thank you very much for presenting this tutorial, I've only ever used Photoshop though I do have (an old) version of GIMP installed and I will now give it a second look. If you have any knowledge in freeware vector graphics programs, a tutorial in efficient conversion of blueprint bitmaps to vector files would come in very handy for me - and I'm guessing a few others here also.
 
I'm joining the thanks to Overscan for this fine tutorial. I didn't know about GMIC, which looks like another fine piece of free software.

In reply to UpForce: I'm no expert here, but I've used the bitmap tracing functionality in Inkscape a couple of times, and I remember that it worked rather well (at least with well-preprocessed "clean" bitmaps). It can be coupled with the excellent SIOX foreground selection method (also available in GIMP btw).

For what is worth, the tracing algorithm bases upon another free tool called "potrace" which may also be used standalone.
 
I've tried bitmap tracing in the past for 3 views and not been that impressed - I'm also not great with vector drawing (I can manage the paths tool in Photoshop OK but that about it) but I might give that a go.
 
To my opinion bitmap tracing isn't really a suitable way for cleaning digital
drawings, because, as bipa already said, results are quite good only for already
"clean" source drawings. But it may be a good way for getting a base drawing
for a modification, or something like that, allthough in most cases re-drawing it
probably is a better way , taking into account the time needed for necessary
changes.
To my experience bit map tracing is sometimes useful, if you need a logo or emblem
for a colour profile, have attached the tiger head of the HAL LCH, just as a quick example.
 

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I use XP-Pen deco 01 art tablet from 2017 or so at work. Both work nicely with GIMP on both Linux and Windows. Gimp is free and I don't need anything better.

GIMP is customizable; recently I have been re-mapping shortcut keys to fit my work flow with animations. I use the L key to turn layers on or off, K to go up one layer and select it, and J to go down one layer and select it. In this way my right hand is free on the tablet to draw or stamp pictoral elements on selected layers, and I avoid "onion skinning".

I am going to re-map all shortcuts, but the important ones are set like layer and brush opacity, merge down, stroke selection etc.
 

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