Chromaticity
Chromaticity is an objective specification of the quality of a
Quantitative description
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. The hue is the angular component, and the purity is the radial component, normalized[clarification needed] by the maximum radius for that hue.
Purity is roughly equivalent to the term "saturation" in the HSV color model. 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.
Some color spaces separate the three dimensions of color into one luminance dimension and a pair of chromaticity dimensions. 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.
These pairs determine a chromaticity as
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.
The xyY space is a cross between the CIE XYZ and its normalized chromaticity coordinates xyz, such that the luminance Y is preserved and augmented with just the required two chromaticity dimensions.[4]
See also
- CIE xyY(chromaticity diagram)
- Chrominance
- rg chromaticity
- Impossible color
- Color index in astronomy
References
- ^ In modern terminology the word "intensity" may refer to lightness, not to colorfulness.
- ^ Emil Wolf (1961). Progress in Optics. North Holland Pub. Co.
- ISBN 978-0-240-51417-8.
chromaticity hue saturation chroma colorfulness purity.
- ISBN 978-1-55860-792-7.
External links
- Stanford University CS 178 interactive Flash demo explaining chromaticity diagrams.
- JOES application software for calculation and plotting of CIE 1931 and 1976 from spectra[1]
- S2CID 105828989.