Color reproduction using vector space projections.

摘要

In this dissertation, we consider the reproduction of colors using vector space projections (VSP). In the first part of the research, we consider the problem of color reproduction subject to material and neighborhood constraints. In practice, we consider the problem of reproducing a target color constrained by maximum additive color signals such as in the phosphorescence process in a monitor. In order to use VSP for constrained color reproduction, we use a novel approach to linearize non-linear CIE-Lab space constraints. As an extension of this research we consider the more difficult problem of reproducing color images subject to constraints on the inaximum primary color variations in a (spatial) neighborhood. We introduce the idea of adjacent color variance (ACV) and then attempt to reproduce colors subject to an upper bound on the ACV.; In the second part of the research, we consider reproduction of color images by color halftoning based on the relationship between a certain class of primaries and the amount of colorants needed to produce those primaries in an on-off i.e., halftone manner. The relationship between the primaries and the colorants is implicitly described in the Neugebauer model/equation, which is an important analytical model for color halftoning. However the Neugebauer equation is not easy to solve because of the highly non-linear relationship between the Neugebauer primaries and the primary CMY (cyan, magenta, yellow) or CMYK (K is black) colorant-amounts needed for color reproduction. In this dissertation we attempt to solve the Neugebauer equation by vector space methods, i.e., by successively projecting onto the constraint sets that define the problem. The method of solution is applicable to any number of primary colorants although our experimental results are confined to the CMY and CMYK cases. Among the constraints we consider are those related to a bound on the permissible total amount of inks (the overwetting constraint) and a bound on the total cost of applying colorants to achieve a satisfactory level of color reproduction.; The experimental results demonstrate that VSP is a feasible approach for solving color reproduction presented in this dissertation.