How to draw lines with GNU Image Manipulation Program. A Left hand position: with Shift key pressed to draw little segments, space bar to move the screen visual along the drawing B Portion of the Image window (at 800% zoom level) showing the drawing guide-line C Right hand position with a common mouse.

 
 
  Part of: Montesanto G (2015) A fast GNU method to draw accurate scientific illustrations for taxonomy. In: Taiti S, Hornung E, Štrus J, Bouchon D (Eds) Trends in Terrestrial Isopod Biology. ZooKeys 515: 191–206. https://doi.org/10.3897/zookeys.515.9459