How Computers Make Books

8 Gray areas

This chapter covers

• Historical methods for printing pictures and reproducing photographs using only black ink and white paper
• Computer methods for printing pictures and reproducing photographs using halftoning and dithering

With only black ink and white paper, we can draw both beautiful letters and good line drawings, such as the diagrams of Bézier curves from chapte 2. But what about reproducing photographs? How can we create the intermediate gray tones using only black ink and white paper? In this chapter, we will look at precomputer methods for the reproduction of gray tones and then see how computers can automate the process.

8.1 Simple thresholding

Consider the two images in figure 8.1: a photograph of a camel and ...