A grayscale image uses only shades of gray to represent an image.
Black-and-white photographs can use a virtually unlimited number of shades of gray, but most computers can display only 16 or 256. To grayscale is to convert a continuous-tone image, like a black-and-white photograph, to an image made up of pixels. Grayscaling is different from dithering, which uses either black or white pixels next to one another to simulate shades of gray. In grayscaling, each individual pixel can be a different shade of gray.