The robust nature of digital signals makes them a very desirable vehicle for communication; but the number of bits required for pictorial images can be very high unless systems are carefully designed to fit the perceptual properties of human vision. Features where important savings can be made in the bit requirements include: adjusting the light level in scanners; using a log or power function instead of a linear function for tonal quantization; allowing for the limited reproduction gamut; using luminance and chrominance signals to achieve bandwidth compression; and allowing for the modulation transfer function of the eye. By these means, large savings in bit requirements have been achieved in both desk-top publishing and broadcast television.

Under a large variety of scene illuminants, a human observer sees the same range of colors; a white piece of paper remains resolutely white independent of the color of light under which it is seen. In contrast, color imaging systems (e.g. digital cameras) are less color constant in that they will often infer the color of the scene illuminant incorrectly. Unless the color constancy problem is solved, color appearance models cannot be used to guide image processing, and such processing is necessary for accurate (and acceptable) color reproduction.In this paper we present a new theory of color constancy, Color by Correlation, which solves for the white-point in images by exploiting the correlation that exists between image colors and scene illuminants. For example, because the reddest red camera measurement can only occur under the reddest red light we say that the reddest camera measurement correlates strongly with the reddest light. Importantly all camera measurements correlate to a greater or lesser degree with different colors of light. By examining the correlation between all image colors and all lights we show that it is possible to make a very accurate estimate of the color of the scene illuminant.Color by Correlation not only performs significantly better than other methods but is a simple, elegant solution to a problem that has eluded scientists working on color for over a century.

Two experiments were conducted to obtain a predictive function for the effect of surround on perceived lightness contrast of pictorial images. Observers matched appearance in lightness contrast reproduction for images with an average surround and a light surround compared to images with a dark surround. Images with a light surround were compared to images with a dark surround under two room lighting conditions: light and dark. The surround effect appears to be overpredicted by currently used color-appearance model parameter values. These parameter values may be more on the order of 1.00:1.16 for lightness contrast reproduction between light-surround and dark-surround viewing conditions and 1.00:1.06 for lightness contrast reproduction between average-surround and dark-surround viewing conditions.

Color is a powerful medium for coding, structuring and emphasizing visual information and, as such, used in many computer applications. However, this tool is less effective, or even counterproductive, in the case of people with impaired color vision. This problem can be remedied to a reasonable extent, provided the display designer is able to anticipate the chromatic trouble spots of a particular color palette. For that purpose, a color editor was designed that allows an image to be displayed as if viewed through the eyes of a color-deficient observer. The model used for computing the color transformations, makes use of state-of-the-art knowledge concerning the polymorphism of human cone pigment and the spectral filtering of the eye lens and macular pigment. As a result, the color editor not only enables the emulation of dichromatic color vision, but also of anomalous trichromatism, the more complex, but also more frequently occurring form of deficient color vision (75% of the colorblind population). In addition to its use as a diagnostic design tool, the editor also provides the means for adjusting the color look-up table to the individual needs of a color-deficient display user.

A universally accepted conclusion about contrast sensitivity functions (CSF's) for spatially modulated sinusoidal gratings is that luminance-modulated CSF's are band-pass, whereas equal luminance chromatically-modulated CSF's are low pass. This conclusion does not follow logically from available data. If the existing chromatic CSF's are compared to low level luminance CSF's, as they should be, then both classes of functions are low-pass. In order to be comparable (possibly) to high level luminance CSF's, chromatic CSF's should be centered at a point in chromaticity space that appears highly saturated, and modulation should be along the line that goes through that point from the spectrum locus to the white point. Very tentative results for two subjects with such purity modulated red gratings show small band-pass effects.

The World Wide Web has become a widely used multi-media platform. The Virtual Reality Modeling Language (VRML) was created to be a standard representation for interactive 3D graphics on the web. Like all web-based publishing, making 3D worlds that are visually similar and effective across browsers and across computing platforms is difficult.The VRML Color Fidelity Working group was formed in early 1997 to try and address some of the color fidelity problems in the VRML specification and implementation. This paper will describe the goals and process the group is using to make VRML worlds “look the same” across all browsers and all platforms. While this work is targeted towards VRML, many of the issues are common to desktop graphics and web-based color in general.

Some of the basic calorimetric characteristics of the CRT monitor were examined These characteristics are closely related to each other. It was found that; 1) CIE model works well for the tone curve characteristics when the CRT monitors are properly calibrated, 2) sRGB's standard monitor characteristics represent reasonably well for the current broadcast monitors, 3) the monitor's gamut is much larger than that of photography and printing, but it does not cover all of the photograph and printing's gamut even with the head/foot room, 4) the monitor's gamut is greatly reduced with the reflection of the ambient illumination. The CRT monitors are rather easy device for the calorimetric characterization, if they were calibrated properly. However, some compensation is necessary if the monitor's characteristics deviates from the ideal set-ups or if it were seen under light illumination.

Advances in microlaser technology are enabling the development of display devices with the extensive color gamuts provided by laser wavelengths. In addition to providing wide gamuts, these devices also are capable of providing accurate and reproducible color in high resolution projection displays. The unique features of such displays are presented and the implications of the expanded color gamut are discussed.

The aim of this paper is to describe five gamut mapping algorithms (GMAs) developed on the basis of the results from a psychophysical experiment evaluating eight previously published algorithms. What follows is a description of the colour reproduction system used, the new algorithms developed and the psychophysical experiments conducted for evaluating the new and existing GMAs.The experimental results suggest that the GCUSP and CARISMA algorithms described in this paper perform most reliably for the test images used in this experiment. Furthermore, the results show that four of the new algorithms perform significantly better than the two algorithms used in the previous experiment.

New color mapping method that is useful for gamut mapping is introduced in this paper. This mapping method is named “Categorical Color Mapping” by authors, because it utilizes the categorical color naming to design color segmentation process. This paper shows concept and algorithm of the categorical color mapping and results of simulation regarding gamut mapping.