GAMUT MAPPING FROM BELOW - FINDING MINIMUM PERCEPTUAL DISTANCES FOR COLORS OUTSIDE THE GAMUT VOLUME

A colorimetrically characterized computer-controlled CRT display was u sed to determine closest perceptual color matches of 25 colors when an exact match was not allowed. An artificial but realistic color gamut was created by intersecting the display gamut with a gamut of a Xerox 4920 color laser printer. Each of 21 observers performed color matches between out-of-gamut colors and those on the artificial gamut's edge. Each observer made color matches on 4 different images. The images re presented some of the categories that business graphic images can fall into. Between the different image types, there ware no multidimension al (MANOVA) statistically significant differences at the 10% confidenc e level in any of the 25 colors tested. The mapping vectors showed tha t (1) observers don't make simple matches as assumed by most gamut-map ping experiments done to date, (2) the influence of image content for simple graphical images tested does not have a large effect when the t ask is to make closest perceptual color matches, and (3) CIELAB hue an gle is not uniform enough, especially in blue and cyan regions, to mak e adequate gamut-mapping transforms. A simple model for clipping type gamut mapping is proposed. Results are clipping type gamut mapping is proposed. Results are compared to predictions of a new gamut-mapping t echnique that minimizes weighted color difference between the target c olor and the gamut boundary. (C) 1997 John Wiley & Sons, Inc.