<Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> </Td> </Tr> </Table> <P> In photography, computing, and colorimetry, a grayscale or greyscale image is one in which the value of each pixel is a single sample representing only an amount of light, that is, it carries only intensity information . Images of this sort, also known as black - and - white or monochrome, are composed exclusively of shades of gray, varying from black at the weakest intensity to white at the strongest . </P> <P> Grayscale images are distinct from one - bit bi-tonal black - and - white images which, in the context of computer imaging, are images with only two colors: black and white (also called bilevel or binary images). Grayscale images have many shades of gray in between . </P> <P> Grayscale images can be the result of measuring the intensity of light at each pixel according to a particular weighted combination of frequencies (or wavelengths), and in such cases they are monochromatic proper when only a single frequency (in practice, a narrow band of frequencies) is captured . The frequencies can in principle be from anywhere in the electromagnetic spectrum (e.g. infrared, visible light, ultraviolet, etc .). </P>

Why are the intensity levels for colors in the range 0 to 255