JPEG lossy compression entails an irreversible mapping of the image to a compressed bit stream, but the standard provides mechanisms for a controlled loss of information. Lossy compression produces a bit stream that is usually much smaller in size than that produced with lossless compression. This chapter describes the structure of the JPEG codec and its units. It examines the role and computation of the discrete cosine transform. Procedures for quantizing the DCT coefficients are also presented followed by a description on the mapping of the quantized DCT coefficients into symbols suitable for entropy coding. Syntactic issues, organization of data units, and alternative modes of operation such as the progressive and hierarchical modes have also been discussed in the chapter.
ASJC Scopus subject areas
- Computer Science(all)