3. Still image compression formats

3.1 Principles

The reduction of information in a still image is achieved by revealing spatial redundancy through the calculation of visual frequencies:

• of low or zero frequency (DC), corresponding to uniform zones with similar coding values, which need not be repeated;

• high frequencies, corresponding to areas of detail, to which the eye is less sensitive, and which can therefore be satisfied with reduced coding.

This transformation in the frequency domain is achieved in particular with two tools.

DCT (Discrete Cosine Transform) (