<title>UltraColor: a new gamut-mapping strategy</title>

Abstract

Many color calibration and enhancement strategies exist for digital imaging systems. Typically, these approaches are optimized to work well with one class of images, but may produce unsatisfactory results for other types of images. For example, a colorimetric strategy may work well when printing photographic scenes, but may give inferior results for business graphics images because of device color gamut limitations. On the other hand, a color enhancement strategy that works well for business graphics images may distort the color reproduction of skintones and other important photographic colors. This paper describes a method for specifying different color mapping strategies in various regions of color space, while providing a mechanism for smooth transitions between the different regions. The method involves a two step process: 1) constraints are applied to some subset of the points in the input color space explicitly specifying the color mapping function; 2) the color mapping for the remainder of the color values is then determined using an interpolation algorithm that preserves continuity and smoothness. The interpolation algorithm that was developed is based on a computer graphics morphing technique. This method was used to develop the UltraColor gamut mapping strategy, which combines a colorimetric mapping for colors with low saturation levels, with a color enhancement technique for colors with high saturation levels. The result is a single color transfonnation that produces superior quality for all classes of imagery. UltraColor has been incorporated in several models of Kodak printers including the Kodak ColorEase PS and the Kodak XLS 8600 PS thermal dye sublimation printers.

Digital color imaging

“…For obtaining similar reproductions on transmissive and reflective media, the use of an invertible color appearance model was reported in [330]. Recently, a gamut mapping strategy for printers that does not involve any explicit clipping and scaling was presented in [331]. The mapping for a limited subset of colors was explicitly specified, and an interpolation algorithm based on morphing was then used to obtain a mapping for the other colors.…”

Psychophysical evaluation of gamut mapping techniques using simple rendered images and artificial gamut boundaries

“…This would apply to the case of pictorial imagery. For computer-generated imagery and business graphics, gamut mapping techniques that alter hue in order to maximize chroma, select particular hues, or perform some other noncolorimetric color-enhancement technique may be more desirable [19].…”

Achieving color uniformity across multi-projector displays

“…Since gamut mapping is a many-to-one mapping, one will not be able to generate the 'gold standard' results produced by the spectroradiometer in the chrominance matching step, unless the color gamuts of all the projectors happen to be within the camera color gamut. However, assuming that the camera has a good gamut mapping algorithm [10,14], the results of the chrominance matching step will be comparable to that achieved by the spectroradiometer.…”