" ... Suddenly an idea flashed. It was simple, and elegant - conventional halftoning is based on little dots - which were usually ellipses of various sizes, oriented at a 45 degree angle (a subtlety based on the visual cortex's distribution of angle detectors... angled ellipses are less perceptually intrusive - except to certain African tribes that grow up in rounded architectures rather than Western Cartesian architected buildings). Digital halftoning aped analog halftoning, which was based on optical screens of repeated patterns - and all the little elliptical dots in a picture, such as a newspaper picture, always leaned in the same direction. My insight was under computer control this did not have to be true; you could make the little dot lean left to represent a zero, and to the right to represent a one - and that this would be essentially perceptially invisible ... "