Image Coding
Lossy or Minimum Distortion Coding
In some image coding applications, a certain amount of distortion may be tolerable.
Higher compression rates may be achieved then, subject to certain fidelity criteria.
Image transforms such as Fourier, Walsh-Hadamard, and Hotelling may be used as the mapping (decorrelating) process in the encoder.
The purpose of the mapping is to reduce the correlation between pixels, and hence improve coding efficiency by processing the transform coefficients, which are independent of one another.