ABSTRACT
This chapter introduces the Joint Photographic Experts Group (JPEG) standard. This standard allows for lossy and lossless encoding of still images, and four distinct modes of operation are supported: sequential discrete cosine transform (DCT)-based mode, progressive DCT-based mode, lossless mode, and hierarchical mode. Image coding is an important application of data compression. When an analog image or picture is digitized, each pixel is represented by a fixed number of bits, which correspond to a certain number of gray levels. In this uncompressed format, the digitized image requires a large number of bits to be stored or transmitted. As a result, compression becomes necessary due to the limited communication bandwidth or storage size. In the sequential coding an image is encoded part-by-part according to the scanning order while in the progressive coding, the image is encoded by multiscanning process and in each scan the full image is encoded to a certain quality level.
