JPEG

Color Space

Discrete Cosine Transform (DCT)

Quantization

Entropy

The final DCT-based encoder processing step is entropy coding. This step achieves additional compression losslessly by encoding the quantized DCT coefficients more compactly based on their statistical characteristics. The JPEG proposal specifies two entropy coding methods: Huffman coding and arithmetic coding.

It is useful to consider entropy coding as a 2-step process. The first step converts the zig-zag sequence of quantized coefficients into an intermediate sequence of symbols. The second step converts the symbols to a data stream in which the symbols no longer have externally identifiable boundaries. The form and definition of the intermediate symbols is dependent on both the DCT-based mode of operation and the entropy coding method.

E-mail comments or suggestions about JPEG to khuri@cs.sjsu.edu or joy@mathcs.sjsu.edu