"It has been said that the great scientific disciplines are examples of giants standing on the shoulders of other giants. It has also been said that the software industry is an example of midgets standing on the toes of other midgets."
- Alan Cooper

GPAA explained
Monday, March 14, 2011 | Permalink

I've added an illustration for the GPAA technique with a little more explanation in the demo description.

The wide line is the geometric edge. The arrows show how the neighbor pixel is chosen. The dashed lines shows the value of line equation for that pixel, which is used to compute the coverage value.