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A color space is the type and number of colors that originate from the combinations of color components of a color model. A color model is an abstract configuration describing how color impression can be created, which consists of color components and rules about how these components interact. The color components have several distinguishing features such as the component type (e.g. hue) and its unit (e.g. degrees, percent) or the type of scale (e.g. linear, non-linear) and its intended number of values referred to as the color depth. "The configuration determines the type and number of colors, which can be created, hence, the resulting color space."〔Opara, E., Cantwell, J. (2014), Best Practices for Graphic Designers, Color Works: Right Ways of Applying Color in Branding, Wayfinding, Information Design, Digital Environments and Pretty Much Everywhere Else, Rockport Publishers, 192 pp.〕 In combination with physical device profiling, it allows for reproducible representations of color, in both analog and digital representations. A color space may be arbitrary, with particular colors assigned to a set of physical color swatches and corresponding assigned names or numbers such as with the Pantone system, or structured mathematically, as with Adobe RGB or sRGB. A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers (e.g. triples in RGB or quadruples in CMYK); however, a color model with no associated mapping function to an absolute color space is a more or less arbitrary color system with no connection to any globally understood system of color interpretation. Adding a specific mapping function between a color model and a reference color space establishes within the reference color space a definite "footprint", known as a gamut, and for a given color model this defines a color space. For example, Adobe RGB and sRGB are two different absolute color spaces, both based on the RGB color model. When defining a color space, the usual reference standard is the CIELAB or CIEXYZ color spaces, which were specifically designed to encompass all colors the average human can see. In other words, colors of a color space are determined by the component values of a color model in relative terms and only then in absolute terms when combined with a reference to the human vision color space. For completeness, it must be added that a "true / absolute" color space requires a specification of the color space's white point and that a screen color space additionally requires a specification of the assumed gamma value. Since "color space" is a more specific term, identifying a particular combination of color model and mapping function, it tends to be used informally to identify a color model, since identifying a color space automatically identifies the associated color model, however this usage is strictly incorrect. For example, although several specific color spaces are based on the RGB color model, there is no such thing as the singular RGB color space. All RGB color spaces have in common the three primary colors (red, green and blue) that mixed in various intensity proportions compose the colors within their colorspaces. Any three wavelengths of light can be mixed in varying proportions to create many different colors but the three primary colors which can be mixed to produce the greatest number of colors are particular wavelengths of red (R), green (G) and blue (B). The specific wavelengths of one R, G and B set give the volume of a specific RGB color space, represented as a cube. Chromaticity (color without regard to intensity) is a function of the ratio between the primaries and when plotted as a function it is known as the 'chromaticity diagram'. In this diagram, the locations of the three primaries are the vertices of a color triangle which is the boundary of the area representing all colors that they can reproduce. Ultimately, any color to be produced by a red-green-blue component system must be specified by those components.〔Joblove, G. H. and Greenberg, D. (1978), Color Spaces for Computer Graphics, Computer Graphics 12 (3), pp20-25〕 In other words, within RGB color spaces, each color can be represented in form of an RGB triplet that can be plotted in a 3D coordinate system known generically as RGB color space and it can be projected in 2D on a chromaticity diagram, but numerically identical RGB triplets can define different colors if additional information about the components is not specified. ==Examples== Colors can be created in printing with color spaces based on the CMYK color model, using the subtractive primary colors of pigment (cyan (C), magenta (M), yellow (Y), and black (K)). Subtractive color systems filter the red, green and blue components of the image from white light using colored filters that modulate only the red, green and blue components of the spectrum. The filter that passes green and blue but modulates red appears cyan while the green-modulating filter appears a purplish-red called magenta, and the blue-modulating filter is yellow. Therefore, the primaries of a subtractive reproduction system are said to be cyan, magenta and yellow but in printing, black ink is added as well, to improve the contrast.〔 To create a three-dimensional representation of a given color space, the amount of magenta color can be assigned to the representation's X axis, the amount of cyan to its Y axis, and the amount of yellow to its Z axis. The resulting 3-D space provides a unique position for every possible color that can be created by combining those three pigments. Colors can be created on computer monitors with color spaces based on the RGB color model, using the additive primary colors (red, green, and blue). A three-dimensional representation would assign each of the three colors to the X, Y, and Z axes. Note that colors generated on given monitor will be limited by the reproduction medium, such as the phosphor (in a CRT monitor) or filters and backlight (LCD monitor). Another way of creating colors on a monitor is with an HSL or HSV color space, based on hue, saturation, brightness (value/brightness). With such a space, the variables are assigned to cylindrical coordinates. Many color spaces can be represented as three-dimensional values in this manner, but some have more, or fewer dimensions, and some, such as Pantone, cannot be represented in this way at all. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「color space」の詳細全文を読む スポンサード リンク
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