On Transparent Quality Image Coding Using Visual Models
Victor Ramamoorthy, Nikil S. Jayant · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1989
Since viewing conditions greatly affect the perception of an image, the coding algorithm must take into account the viewing conditions and the human visual perception mechanisms. If the coded image and the uncoded input image are indistinguishable in a casual viewing session lasting 20 seconds, then the coding algorithm is said to have attained Transparent quality. The smallest bit rate at which such transparent quality is achieved is called the perceptual entropy. Starting with a low bit rate vector quantizer which does not offer transparent quality encoding, we explore a technique with which perceptually relevant regions can be carefully encoded to achieve transparent and high quality reproductions. The bit rates associated with this technique are in the range of 1 to 3.5 bits/pixel and these can be regarded as an upper bound to the perceptual entropy.