RENDERING:
- digital image compositing modes: http://keithp.com/~keithp/porterduff/
- curve_to approximation:
  http://graphics.cs.ucdavis.edu/GraphicsNotes/Divide-and-Conquer-Bezier-Curve/Divide-and-Conquer-Bezier-Curve.html
  http://www.cs.mtu.edu/~shene/COURSES/cs3621/NOTES/
- geometry primitives: http://astronomy.swin.edu.au/~pbourke/geometry/
- hershey vector fonts: http://astronomy.swin.edu.au/~pbourke/other/hershey/
