High quality image coding with a model-testing vector quantizer and a human visual system model

A class of image quantizers called model-testing vector quantizers is introduced. These are finite-state quantizers with the additional ability to make a decision about whether the current input conforms to the assumed finite-state model or not. The nonconforming component is coded at relatively lower bit rates by utilizing well-known linear and nonlinear properties of the human visual system. An adaptive spatial and intensity quantization procedure is used that removes the perceptually irrelevant information from the nonconforming component. The differential brightness discrimination of the eye is also utilized. Resulting coded images are indistinguishable from the originals at bit rates that range from 1.0 to 3.5 bits/pixel for a wide variety of 512×512 images. These bit rates can be regarded as upper bounds for the perceptual entropy of the corresponding images