The quality of the graphics output on a computer printer is measured in dpi (dots

per inch). Simply by changing the density of dots than make up each part of an

image, the printer can produce graphics that look almost photographic.  To

understand how this works, consider how a black-and-white photograph shows the

shades which, in real life, are colors.  Each color is a different shade of gray.  For

graphics to be produced on the computer printer, a piece of software called a

printer driver decides upon a dot pattern which will represent each color shade. 

These different patterns or textures each create an individual effect which your eye

translates into gray shades.  The closer you look at the image, however, the less

lifelike it looks.

According to the passage, a computer printer can