Script-Fu -> Inkpen

This is an adjustable script which renders the original image as if drawn with an ink pen. The settings in the dialog made can make a huge diference in the results. Also a major consideration is the light/color contrast in the original image. Perhaps the most important setting is the "brightness", but ink color as well as the stroke length are also adjustable, and there are toggles for making outlines bolder and creating a blue background grid.

The examples will illustrate this...

; This script should be placed 
; in the user or system-wide script folder.
;
; Windows Vista/7/8/10)
; C:\Program Files\GIMP 2\share\gimp\2.0\scripts
; or
; C:\Users\YOUR-NAME\.gimp-2.8\scripts
; 
; Windows XP
; C:\Program Files\GIMP 2\share\gimp\2.0\scripts
; or
; C:\Documents and Settings\yourname\.gimp-2.8\scripts   
; 
; Linux
; /home/yourname/.gimp-2.8/scripts  
; 
; Linux system-wide
; /usr/share/gimp/2.0/scripts
;