In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element of a raster image. In a display device, dot matrix printer, or ASCII art a pixel is the smallest element whose output can generally be controlled independently.
The concept of a picture element dates to the earliest days of electronic imaging. The German word Bildpunkt ("picture point") appeared in an 1888 patent, while the English term picture element appeared in U.S. patents filed as early as 1911. The word pixel was first published in 1965.
Pixels are usually arranged in a regular two-dimensional grid, with each pixel storing one or more numerical values that represent a sample of an image. A greater sampling density can represent finer spatial detail, although the result also depends on the optics, sensor, processing, and display. In color imaging, a pixel is commonly represented by components such as red, green, and blue (RGB), or cyan, magenta, yellow, and black (CMYK).
In some contexts (such as descriptions of camera sensors), pixel refers to a single scalar element of a multi-component representation (called a photosite in the camera sensor context, although sensel 'sensor element' is sometimes used), while in yet other contexts (like MRI) it may refer to a set of component intensities for a spatial position.
Software on early consumer computers was necessarily rendered at a low resolution, with large pixels visible to the naked eye; graphics made under these limitations may be called pixel art, especially in reference to video games. Modern computers and displays, however, can easily render orders of magnitude more pixels than was previously possible, necessitating the use of large measurements like the megapixel (one million pixels).
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