A color image coding method by using KL transformation for vector function : The algorithm and the experiment result using the RGB color system

Abstract

A color image is represented by a vector function C^^→=f^^→(x,y) that represents a mapping from a position (x, y) in 2-D plane to a vector C^^→ that represents single color. Taking this fact into account, authors have newly devised a KL transformation for vector function, and applied the transformation to color image coding. The coding method is as follows: (1) Expand a color image f^^→(x,y) in terms of a set of orthonormal vector functions <φ^^→>^<(u)>(x,y) as follows: f^^→(x,y) =Σ_ua_u<φ^^→>^<(u)>(x,y). (2) Transmit the coefficients of the expansion a_u as information of the image. An experiment of the coding method was made on the basis of the RGB color system. The result of the coding method was far better than the JPEG method.