Aliasing 走样

Computer Science An Overview _J. Glenn Brookshear _11th Edition

Have you ever noticed the weird “glittery” appearance that striped shirts and ties

have on television screens? This is the result of the phenomenon called

aliasing,

which occurs when a pattern in the desired image meshes inappropriately with the

density of the pixels comprising the image. As an example, suppose a portion of the

desired image consists of alternating black and white stripes but the center of all

the pixels happens to fall only on the black stripes. The object would then be ren-

dered as being completely black. But, if the object moves slightly, the center of all the

pixels may fall on the white stripes, meaning that the object would suddenly change

to white. There are a variety of ways to compensate for this annoying effect. One is to

render each pixel as the average of a small area in the image rather than as the

appearance of a precise single point.