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Representing colors as three numbers [color graphics] | IEEE Journals & Magazine | IEEE Xplore

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RGB in graphics is both a way of specifying color and a way of viewing color. Graphics algorithms manipulate RGB colors, and the images produced by graphics algorithms are encoded as RGB pixels and displayed on devices that render these pixels by emitting RGB light. Colored images are also used to specify color in graphics. Most computer graphics texts and tutorials provide a description of human color vision and measurement as defined by the CIE tristimulus values, XYZ. Often missing, however, is an in-depth discussion of the relationship between the different applications of RGB and XYZ, and any discussion of color models beyond trichromacy. The goal of this tutorial is to provide a complete, concise analysis of RGB color specification and its relationship to perceptual and physical specifications of color, and to introduce some models for color perception beyond tristimulus theory.

Representing Color as Three Numbers That color can be represented by three numbers-whether RGB or XYZ-is a direct result of the physiology of human vision. Electromagnetic radiation whose wavelength is in the visible range (370 to 730 nanometers) is converted by photopigments in the retinal cones into three signals, which correspond to the response of the three types of cones. This response is a function of wavelength and is described by the spectral sensitivity curves for the cones, as Figure 1 shows. Fig. 1: Spectral sensitivity curves for the short (blue), medium (green), and long…

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