On the other hand, some color spaces such as RGB and XYZ do not separate out chromaticity, but chromaticity is defined by a mapping that normalizes out intensity, and its coordinates, such as r and g or x and y, can be calculated through the division operation, such as x = X / X + Y + Z, and so on. Other coordinate systems on the same X-Y-Z triangle, or other color triangles, can be used. These x and y are used because of simplicity of expression in CIE 1931 (see below) and have no inherent advantage. These pairs determine a chromaticity as affine coordinates on a triangle in a 2D-space, which contains all possible chromaticities. This presentation is a projective transformation of the CIE 1931 chromaticity diagram above. ( u′, v′), the chromaticity in CIELUV, is a fairly perceptually uniform presentation of the chromaticity as (another than in CIE 1931) planar Euclidean shape. For example, the white point of an sRGB display is an x, y chromaticity of (0.3127, 0.3290), where x and y coordinates are used in the xyY space. Some color spaces separate the three dimensions of color into one luminance dimension and a pair of chromaticity dimensions. The property " hue" is as used in general color theory and in specific color models such as HSL and HSV color spaces, though it is more perceptually uniform in color models such as Munsell, CIELAB or CIECAM02. Purity is roughly equivalent to the term " saturation" in the HSV color model. The hue is the angular component, and the purity is the radial component, normalized by the maximum radius for that hue. In color science, the white point of an illuminant or of a display is a neutral reference characterized by a chromaticity all other chromaticities may be defined in relation to this reference using polar coordinates. This number of parameters follows from trichromacy of vision of most humans, which is assumed by most models in color science. Chromaticity consists of two independent parameters, often specified as hue (h) and colorfulness (s), where the latter is alternatively called saturation, chroma, intensity, or excitation purity. 3D Chromaticity Diagram of the WideGamutRGB color spaceĬhromaticity is an objective specification of the quality of a color regardless of its luminance.
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