04/18/2002
15-462 Graphics I
22
Halftone Screens
•Regular
patterns create some artefacts
–Avoid
stripes
–Avoid
isolated pixels (e.g. on laser printer)
–Monotonicity:
keep pixels on at higher intensities
•Example
of good 3£3 dithering matrix
–For
intensity n, turn on pixels 0..n–1
