An amazing example of abstraction is line drawings. How can so few lines capture form so well?
Line drawings clearly build upon perceptual mechanisms, since we know early vision involves edge detection. Yet, if you simply run an edge detector over an image, you don?t get a very good line drawing. Lines seem to convey more information than just intensity gradients. They seem to show the most important edges. Perceptual psychologists still do not have a good theory of line drawings.
I consider the problem of what are the best lines to draw to be one of the more interesting problems in computer graphics and visual cognition. DeCarlo et al. recently published a clever new idea. They propose the use of suggestive contours, contours that may appear given small perturbations in position. When added to a line drawing containing only silhouettes, the resulting line drawing is much better. But we are still a long way from Picasso or Matisse.