PIXEL

Pixel, short for picture element, is the smallest addressable element in a digital image or display. In a raster image, the image is organized as a two-dimensional grid of pixels; each pixel encodes color and brightness information for a small portion of the picture. Typically, color pixels store data in one or more color channels—most commonly red, green, and blue (RGB). A pixel’s color is determined by the combination of its channel values; the overall image quality can be described by the color depth per channel (for example, 8 bits per channel, yielding 24-bit color) and by the total pixel count.

The term pixel is a portmanteau of picture element and was popularized in the 1960s–1970s in computer graphics as raster displays and digital imaging developed. In printing there is a related concept of dots, but digital images used on screens are composed of discrete pixels.

On displays, pixels are laid out in a regular grid; each pixel is typically made from subpixels in red, green, and blue. Different display technologies arrange subpixels differently (for example, stripe or PenTile layouts). Pixel density, measured in pixels per inch (PPI) for screens and dots per inch (DPI) for printed output, affects perceived sharpness. Resolution is usually stated as width × height in pixels (for example, 1920×1080).

In digital cameras and scanners, the sensor provides a grid of photosites that, after processing (and sometimes demosaicing, in color sensors using a Bayer filter), produce a full-color image at a given pixel resolution. Larger pixel counts enable higher detail but must be matched to optics and processing capabilities.