View Full Version : Need some help capturing line drawing from graph paper

05-02-2010, 06:46 PM
Greetings ~ I am new to the guild, and am really quite amazed by this community.

My project is really quite basic - I have a collection of photocopied hand-drawn diagrams which were originally done on graph paper in pencil. I am attempting to digitize the diagrams, losing the graph lines and capturing only the site map diagrams. I have tried a couple of things using GIMP, but it is going to take forever to completely lose any evidence of the graph lines the way I am fumbling about with it. My GIMP skills are fairly basic, there must be more straightforward techniques from harvesting only the drawn lines. Should you be so kind as to respond, please be very specific in your directions .... I may not know HOW to do something that you might suggest.

Many thanks!!

05-02-2010, 07:07 PM
Hi YazzieGirl, and welcome!

Can you upload one of your scans? There are quite a few tricks that might help, but it'd be easiest if we could see what you're working with.

05-02-2010, 07:17 PM
If you have scanned them in color or greyscale then keep them like that - i.e. dont drop them to two color yet as most of the techniques to get rid of the graph lines need something to key on. What we use depends on what you have but will either be color or luminance. You also need high res too so no dropping the res to upload here - we can take up to about 5K pix square which is pretty big. Also PNG would be better than JPG but there is a 4Mb or so file size limit too. If you cant manage to upload it all then a small section is better than a rescaled page and we will show what to do for you to replicate that on the whole page.

05-02-2010, 07:33 PM
Redrobes and Gidde ~ I have edited the original post with a small selection from one diagram. It is a jpg, could change it to png, if needed.

05-02-2010, 08:01 PM
Ok, your in big trouble here. The problem is that because they are photocopied then its turned all the lines into uniform color so there is no color difference between what you want and what you don't want. Next is luminosity - same. Its either black or white. That leaves the pattern and the pencil lines are about as thick as the grid which is also difficult to distinguish between them. So your not left with many options. I have a very special program which is not part of Gimp native but can be accessed with some extra plugins or something - I dont do Gimp. Anyway, this program looks for a grid like pattern and then removes it but in that process will remove some of the line info as well. You have the almost pathalogical case to deal with.

Can you get the original non photocopied versions of the maps and get them scanned in with a flatbed in color or at least greyscale so there is something to key on. Here is my best shot. Its not very good I would admit.

05-02-2010, 08:09 PM
Redrobes - this is precisely what I thought was going to be the case ... I will see if I can get my hands on the original drawings (I work remotely, so this may take me some time).

I am more familiar with CorelDraw than I am with GIMP. Are there other open source softwares that may be better suited for this project?

Thank you for your help!

05-02-2010, 08:18 PM
I must admit that I use a variety of non standard tools so there may be others better suited to answer app specific questions but I will say that Gimp is free and open source. Also Xara is open source for Linux but closed for windows I believe. Not sure if either of these would be suitable for the case you have attached tho I reckon if you got something where the pencil was gray and the grid was light blue, or a different shade of gray even or that you had something else to key on then either Gimp or Xara would probably be able to do something better than my result. Normally this sort of thing can be done quite successfully.

05-02-2010, 09:20 PM
not to go back to the dark ages... but your best bet would be to head to an office store, by some quality tracing vellum, a nice set of pens and then trace the parts you want. Scan in the new black and white linework and add the text back in if needed using some app. The result would be ultra clean.

05-02-2010, 09:21 PM
I've gotta say Redrobes has it nailed :( If this was my project, I'd probably be tracing over the stuff I wanted to keep, redrawing it on a new transparent layer so the old can be hidden/deleted.

05-02-2010, 10:07 PM
Sure there all sorts of fancy things to do...knobs to push, dials to turn, but why? If you had the cyan grid it could have taken about 10 seconds...select by color, new layer, fill with white. I did try to blur the whole thing by .5 then max out the contrast and brightness and that was fairly decent but required going back and hand-painting white over a large amounts of dots...would have taken 5 minutes. So, I just traced it by hand in Ps, 5 minutes.

05-02-2010, 10:21 PM
If I had CorelDraw, I could do this. Unfortunately, I only have GIMP to work with for now. There has to be a trace function using GIMP, separating the traced layer from the original. I haven't been able to figure it out, and the GIMP user manual isn't much use. Grrrr ..... I was hoping to avoid investing in software .....

05-03-2010, 02:13 AM
Adobe Illustrator has a Live Trace function which might be tweakable for what you're trying to do - inkscape is the open source version, perhaps it can do something similar...

05-03-2010, 06:15 AM
What you need is to create a new layer, trace by hand over the original on the new layer, maybe in red or something like that to distinguish the two, and then delete the old layer. The exact details about which menus and buttons to push for creating or selecting which layer your on I will leave to the Gimpers. I think Devin probably has the easiest solution given the type of map your trying to extract - unless this is a pretty simple part of a very extensive or complex set of them.