In digital imaging, a pixel is a physical point in a raster image, or the smallest, controllable element of a picture represented on the screen. The address of a pixel mostly corresponds to its physical X and Y coordinates.
Each pixel is a color sample of the original image. In color image systems, a color is typically represented by three or four color component or channels such as red/green/blue (RGB) or cyan/magenta/yellow/black (CMYK). A extra channel of transparency (alpha) may be added.