Scan Modes

PCs represent pictures in a variety of ways – the most common methods being are line art, halftone, greyscale, and colour:

  • Line art is the smallest of all the image formats. Since only black and white information is stored, the computer represents black with a 1 and white with a 0. It only takes 1-bit of data to store each dot of a black and white scanned image. Line art is most useful when scanning text or line drawing. Pictures do not scan well in line art mode.
  • While computers can store and show greyscale images, most printers are unable to print different shades of grey. They use a trick called halftoning. Halftones use patterns of dots to fool the eye into believing it is seeing greyscale information
  • Greyscale images are the simplest of images for the computer to store. Humans can perceive about 255 different shades of grey – represented in a PC by a single byte of data with the value 0 to 255. A greyscale image can be thought of as equivalent to a black and white photograph
  • True colour images are the largest and most complex images to store, PCs using 8-bits (1 byte) to represent each of the colour components (red, green, and blue) and therefore 24-bits in total to represent the entire colour spectrum.