When I was in the sixth grade, I saw a picture like the one shown in Figure 7-1 but couldn’t quite figure out what it was. After squinting at it for a while, I eventually figured it out. (Turn the book upside down, and view it from across the room. I won’t tell anyone.)

The puzzle works because of how the human eye functions. The low-resolution, blocky image shown in the figure is hard to recognize up close, but when it is seen from a distance, you know what it represents because your eyes perceive less detail, which makes the edges smooth.

A photomosaic is an image that works according to a similar principle. You take a

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