Lossless coding of color images using color space transformations

The key issue in the development of lossless compression techniques has been the manipulation of the image model from a probabilistic point of view in order to reduce the bit rates as represented by the entropy of such a model. In this respect, arithmetic coding using adaptive models shows excellent performance and is easy to implement. On the other hand, many studies have been dedicated to find suitable ways to represent a color image based on the human visual response to color changes in magnitude, frequency and direction. Many of these studies have resulted in linear and nonlinear transformations of the well-known RGB and tristimulus color spaces that describe a color image in different planes, each of those being a function of the illuminance and chrominance of each pixel. Application of lossless coding techniques to these transformed color planes, such as L*a*b*, has resulted in improved performances compared to those in RGB planes.