increased contrast

Here i have added in darker lines..

In this first example, the contrast isn't very intense..

 So i darkened the lines.. however this revealed that the darker lines were quite randomly placed and weren't quite fitting in very well.

I thought back to painting theory I had researched in the past, and remembered the idea of chiaroscuro (having clear tonal contrasts) and the fact that contrast is most effective when the lightest parts are placed directly next to the darkest parts. So therefore I altered the code so that the light and dark parts run along the same general curves. This was the result: