Color Gamut Mapping along Electrostatic Field Lines

Abstract

Most gamut mapping methods project out-of-gamut colors onto the in-gamut colors using a device independent color space (such as CIELAB) with constraints on hue and lightness. Results depend significantly on the shape of the gamut. Especially in the case of concave gamuts, continuous transitions between colors while preserving chroma and lightness are hard to obtain.We propose a gamut mapping method based on a physical model: the trajectory of a charged particle along electrostatic field lines induced by charges placed on the surface of the gamut. Since an electrostatic field is free of divergence, every out-of-gamut color is uniquely mapped onto a gamut surface point. The distribution of the charges on the surface can be used to influence the mapping.In Océ's new Color Production System (CPS 700), colors are formed by adhesively collecting seven different toners. Consequently, mixed colors consist of toner particles beside each other and not on top of each other, giving the color gamut a concave shape. Our method yields smoother transitions between colors than any other method we have tried.The paper will discuss the need for continuous gamut mappings, the field line method and its benefits for transitions between monocolors in the CPS 700.