COLOR IMAGE CORRECTION FOR SCANNER AND PRINTER USING B-SPLINE CMAC NEURAL NETWORKS

Abstract

The process of eliminating the color errors from the gamut mismatch, resolution conversion, and nonlinearity between scanner and printer is usually recognized as an essential issue of color reproduction. This paper presents a new formulation based on the generalized inverse plant control for the color error reduction process. In our formulation, the printer input and scanner output correspond to the input and output of a system plant, respectively. Obviously, if the printer input equals the scanner output, then there are no color errors involved in the entire system. In other words, the plant becomes an identity system. To achieve this goal, a plant generalized inverse should be identified and added to the original system. Since the system of a combination of both scanner and printer is highly nonlinear, CMAC-based neural networks, which have the capability to learn arbitrary nonlinearity, are applied to identify the plant generalized inverse. CMAC network is a perceptron-like feedforward structure with associative memory properties. Its memory requirements can be greatly reduced by the use of hash coding techniques. In order for CMAC networks to construct high-order, smooth, nonlinear plant inverse, more general CMAC addressing schemes have been proposed in conjunction with use of B-spline receptive functions. It is shown that B-spline CMAC networks learn orders of magnitude more rapidly than typical implementations of back propagation in the multilayered neural networks, due to the local nature of its weighting updating and the finite support of B-spline receptive field functions. Finally, a number of test samples are conducted to verify the effectiveness of the proposed method.