Most computer graphics images are presented to the user on some kind of raster display. Raster displays show images as rectangular arrays of pixels. Rasters are also prevalent in input devices for images. A digital camera contains an image sensor comprising a grid of light-sensitive pixels, each of which records the color and intensity of light falling on it. The corresponding disadvantage is that they must be rasterized before they can be displayed. Vector images are often used for text, diagrams, mechanical drawings, and other applications where crispness and precision are important and photographic images and complex shading aren’t needed. The chapter discusses the basics of raster images and displays, paying particular attention to the nonlinearities of standard displays. An ink-jet printer is an example of a device that forms a raster image by scanning. A raster input device has to make a light measurement for each pixel, and they are usually based on arrays of sensors.