On the Rendition of Unprintable Colors

Exact reproduction of the colors input to a Color Electronic Prepress System (CEPS) by a scanner is seldom possible, since the gamuts of colors for input and output media rarely match. Input colors which cannot be printed on a given output medium must be mapped into printable colors in such a way as to yield pleasing results. This process of compressing the input gamut so as to be compatible with the output gamut has traditionally been performed by scanner operators. In a modern CEPS, however, gamut compression can be carried out automatically, subject to editorial consent by the user. In this paper we discuss a mathematical formalism for describing gamuts and mapping from one to another, with emphasis on the advantages of using a uniform color space.