High Performance Images

Chapter 2. The Theory Behind Digital Images

Yoav Weiss

Images are an essential part of human history. Film-based photography has made the creation of images easy—it captures a moment in time by allowing light to go through a lens and hit film, where an array of minuscule grains of silver-based compound change their brightness as a response to light intensity.

With the advent of computers, soon came the digitization of photos, initially through the scanning of printed images to digital formats, and then through digital camera prototypes.

Eventually, commercial digital cameras started showing up alongside film-based ones, ultimately replacing them in the public’s eye (and hand). Camera phones also contributed, with most of us now walking around with high-resolution digital cameras in our pockets.

A digital camera is very similar to a film-based one, except instead of silver grains it has a matrix of light sensors to capture light beams. These photosensors then send electronic signals representing the various colors captured to the camera’s processor, which stores the final image in memory as a bitmap—a matrix of pixels—before (usually) converting it to a more compact image format. This kind of image is referred to as a photographic image, or more commonly, a photo.

But that’s not the only way to produce digital images. Humans wielding computers can create images without capturing any light by manipulating graphic creation software, taking screenshots, or many other means. We usually ...