Color gamut mapping and the printing of digital color images

Abstract

Principles and techniques useful for calibrated color reproduction are defined. These results are derived from a project to take digital images designed on a variety of different color monitors and accurately reproduce them in a journal using digital offset printing. Most of the images printed were reproduced without access to the image as viewed in its original form; the color specification was derived entirely from calorimetric specification. The techniques described here are not specific to offset printing and can be applied equally well to other digital color devices.The reproduction system described is calibrated using CIE tristimulus values. An image is represented as a set of three-dimensional points, and the color output device as a three-dimensional solid surrounding the set of all reproducible colors for that device, called its gamut. The shapes of the monitor and the printer gamuts are very different, so it is necessary to transform the image points to fit into the destination gamut, a process we call gamut mopping. This paper describes the principles that control gamut mapping. Included also are some details on monitor and printer calibration, and a brief description of how digital halftone screens for offset printing are prepared.

Digital color imaging

“…Stone et al [158] laid down some principles of gamut mapping that were culled from psychophysics and accepted procedures in graphic arts. For printing images displayed on CRT monitors, they described an interactive gamut mapping strategy involving translation, scaling, and rotation of colors in CIE XYZ space.…”

Evaluation of Algorithms for the Determination of Color Gamut Boundaries

“…A simple approximation of the gamut can be found by measuring the colors that make up the extreme points of the gamut. Stone et al 11 proposed that the gamut can be represented by planes connecting these extreme points.…”

An interactive tool for gamut masking

“…Some interactive gamut mapping tools have been developed, but they lack the flexibility to allow users to create their own gamut masks and change local image colors. Stone et al 7 and Kalra 8 let users vary transformation parameters for translation, rotation, and scaling transformations performed on the gamut. Farup and Hardeberg 9 propose a tool in which a user can interactively change the gamut surface by moving tetrahedra on the gamut boundary.…”