JPEG

Color Space

DCT

Entropy

Quantization

After output from the DCT, each of the 64 DCT coefficients is uniformly quantized in conjunction with a 64-element Quantization Table, which must be specified by the appliation (or user) as an input to the encoder. Each element can be any integer value from 1 to 255, which specifies the step size of the quantizer for its corresponding DCT coefficient.

The purpose of quantization is to achieve compression by representing DCT coefficients with no greater precision than is necessary to achieve the desired image quality. In other words, the goal of this processing step is to discard information which is not visually significant.

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