
5.1 Transform Compression 117
distortion, is there a minimum number of bits that are needed to represent
the picture? The first question is answered in the following sections where we
discuss various two-dimensional picture-compression techniques that (at the
cost of a small amount of distortion, often unnoticeable) significantly
economize on the number of bits required for a picture. The second question
is answered by the rate-distortion function, which will be discussed in con-
ceptual terms at the end of the chapter.
Suppose the given picture is to be received by a system the spatial and
gray scale resolution of which exceeds or at leas