Many displays and hardcopy devices produce images of only two intensity levels. For example, most laser printers print images as arrays of black dots on white paper. The process of transforming an image composed of gray levels to a form that can be reproduced with just two tones is known as halftoning. The vision system’s limited acuity causes the images to be perceived as if they were composed of shades of gray. If the two-tone pattern is not fine or random enough, however, image quality will suffer.

This paper describes three techniques for halftoning. The first two use halftone fonts--one composed of fixed, clustered dots, and the other of randomly dispersed dots. With the third technique, images are converted to a standard format, allowing the halftoning to be performed by commercial desktop publishing software. The author provides a clear analysis of speed, quality, and cost tradeoffs. The paper is well balanced in that it shows how the three techniques relate to other approaches, beginning with 19th-century photomechanical processes.