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## A Brief History of the Pixel

Computer graphics legend Alvy Ray Smith (Pixar, Lucasfilm, Microsoft) has written a new book called A Biography of the Pixel (ebook). In this adapted excerpt, Smith traces the origins of the pixel โ which he calls “a repackaging of infinity” โ from Joseph Fourier to Vladimir Kotelnikov to the first computers to Toy Story.

Taking pictures with a cellphone is perhaps the most pervasive digital light activity in the world today, contributing to the vast space of digital pictures. Picture-taking is a straightforward 2D sampling of the real world. The pixels are stored in picture files, and the pictures represented by them are displayed with various technologies on many different devices.

But displays don’t know where the pixels come from. The sampling theorem doesn’t care whether they actually sample the real world. So making pixels is the other primary source of pictures today, and we use computers for the job. We can make pixels that seem to sample unreal worlds, eg, the imaginary world of a Pixar movie, if they play by the same rules as pixels taken from the real world.

The taking vs making โ or shooting vs computing - distinction separates digital light into two realms known generically as image processing and computer graphics. This is the classical distinction between analysis and synthesis. The pixel is key to both, and one theory suffices to unify the entire field.

Computation is another key to both realms. The number of pixels involved in any picture is immense - typically, it takes millions of pixels to make just one picture. An unaided human mind simply couldn’t keep track of even the simplest pixel computations, whether the picture was taken or made. Consider just the easiest part of the sampling theorem’s ‘spread and add’ operation - the addition. Can you add a million numbers? How about ‘instantaneously’? We have to use computers.