How to CG a picture without an expensive photo program, and without paying a cent…
1. Go to gimp.org and download and install GTK+ libraries for Windows and GIMP.
2. Start GIMP and open the scanned-in picture you made.
3. From the Layer menu, click on New Layer.
4. Name the new layer, something like Transparency, to get the point across.
(you will now be working on the new layer like a transparent sheet over the original drawing.)
5. Save the file you have so far as an XCF file. (File – Save As – Determine File Type – XCF)
6. Select the Paths option from the Tools menu, which looks like a pen drawing a line with three squares lined up by it.
7. From the Paths Options toolbar, make sure your edit mode is in Design.
8. Where a straight or curved line starts, click there. Click on all the major points on the line, where the curves change or become straight, etc.
9. Change the Edit Mode to Edit.
10. To make a curve, select the area between two circles and drag until you have the curve you want.
11. Once you are done making the path you want, click Stroke Path. The Stroke Width should be around 6.0 pixels (try 4.0 for more detailed areas), the Joint Style should be curved, and the Cap Style should be (the producer’s idea, not mine) butt.
12. Select another tool from the tools menu, and then reselect Paths.
13. Repeat steps 6 through 12 to make each of the lines you need.
General Hints:
- If you don’t like a line, press Ctrl+Z
- Once finished, you can get rid of the below layer with Layer > Stack > Select Bottom Layer, then Layer > Delete Layer.
DISCLAIMER: I in no way intend to advertise for GIMP. If this doesn't work, I'll figure out why.