[Award Winner] Drawing hand drawn maps in Gimp

[torstan]

An alternative way to get a line drawing into gimp is to scan a hand drawn map. For example here's the hand drawn map of Dragonford:



If you have a scan like this you can place it over your parchment in a number of ways.

First open the base image of a parchment background as above. Now open your scanned image in a separate window. Scale the scanned image so that its dimensions are within the size of the parchment image you will be using as your background. Select-all and copy the scanned image. Now go to your parchment image and create a new transparent layer.

---Useful tangent---
Note that shift-clicking the new layer button in the layers dialogue creates a new layer with the last used values. This saves ages when creating lots of new layers like we will be doing here.
---end of tangent

Paste the copied image into this new layer. You will now have something that looks like this:



Now this is no use to anyone right now. We need to get rid of the white background. The easiest way to do this is to change the layer mode from normal to multiply.



This gives something that looks like this:



Note that there is a strange artefact around the edge of the old white image. This is there because the background wasn't as white as it looked. To get rid of this we need to mess with the levels. Make sure the layer with the scanned image is selected. Go to Color->Levels. There is a histogram under which there is a black triangle (far left), a grey triangle (middle) and a white triangle (far right). If your histogram looks anything like mine then there should be a large peak in the histogram at the right hand side. This is just saying that most of the image is white - not surprising for a scanned image on white paper. The width of this peak shows that there is a spread of 'whites' away from the true white marked by the white triangle. This is what causes the artefacts seen above. Slide the white triangle to the left of this large peak. Now every region that was just off-white will be pure white. Your artefacts should have disappeared, leaving you with an image something like this: