Color model
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In
This article describes ways in which human color vision can be modeled, and discusses some of the models in common use.
Tristimulus color space
One can picture this space as a region in three-dimensional
The human tristimulus space has the property that additive mixing of colors corresponds to the adding of vectors in this space. This makes it easy to, for example, describe the possible colors (gamut) that can be constructed from the red, green, and blue primaries in a computer display.
CIE XYZ color space
One of the first mathematically defined color spaces is the CIE XYZ color space (also known as CIE 1931 color space), created by the International Commission on Illumination in 1931. These data were measured for human observers and a 2-degree field of view. In 1964, supplemental data for a 10-degree field of view were published.
Note that the tabulated sensitivity curves have a certain amount of arbitrariness in them. The shapes of the individual X, Y and Z sensitivity curves can be measured with a reasonable accuracy. However, the overall
Sometimes XYZ colors are represented by the luminance, Y, and chromaticity coordinates x and y, defined by:
- and
Mathematically, x and y are projective coordinates and the colors of the chromaticity diagram occupy a region of the real projective plane. Because the CIE sensitivity curves have equal areas under the curves, light with a flat energy spectrum corresponds to the point (x,y) = (0.333,0.333).
The values for X, Y, and Z are obtained by integrating the product of the spectrum of a light beam and the published color-matching functions.
Additive and subtractive color models
RYB color model
RYB is a
RGB color model
Media that transmit light (such as television) use
Other primary colors could in principle be used, but with red, green and blue the largest portion of the human color space can be captured. Unfortunately there is no exact consensus as to what loci in the
RGB is a device-dependent color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual red, green, and blue levels vary from manufacturer to manufacturer, or even in the same device over time.[11][12] Thus an RGB value does not define the same color across devices without some kind of color management.[13]
CMY and CMYK color models
It is possible to achieve a large range of colors seen by humans by combining cyan, magenta, and yellow transparent dyes/inks on a white substrate. These are the subtractive primary colors. Often a fourth ink, black, is added to improve reproduction of some dark colors. This is called the "CMY" or "CMYK" color space.
The cyan ink absorbs red light but transmits green and blue, the magenta ink absorbs green light but transmits red and blue, and the yellow ink absorbs blue light but transmits red and green. The white substrate reflects the transmitted light back to the viewer. Because in practice the CMY inks suitable for printing also reflect a little bit of color, making a deep and neutral black impossible, the K (black ink) component, usually printed last, is needed to compensate for their deficiencies. Use of a separate black ink is also economically driven when a lot of black content is expected, e.g. in text media, to reduce simultaneous use of the three colored inks. The dyes used in traditional color photographic prints and slides are much more perfectly transparent, so a K component is normally not needed or used in those media.
Cylindrical-coordinate color models
A number of color models exist in which colors are fit into
Background
Different color theorists have each designed unique
Pure, saturated hues of equal brightness are located around the equator at the periphery of the color sphere. As in the color wheel,
The vertical axis of the color sphere, then, is gray all along its length, varying from black at the bottom to white at the top. All pure (saturated) hues are located on the surface of the sphere, varying from light to dark down the color sphere. All impure (unsaturated hues, created by mixing contrasting colors) comprise the sphere's interior, likewise varying in brightness from top to bottom.
HSL and HSV
HSL and HSV are both cylindrical geometries, with hue, their angular dimension, starting at the red primary at 0°, passing through the green primary at 120° and the blue primary at 240°, and then wrapping back to red at 360°. In each geometry, the central vertical axis comprises the neutral, achromatic, or gray colors, ranging from black at lightness 0 or value 0, the bottom, to white at lightness 1 or value 1, the top.
Most televisions, computer displays, and projectors produce colors by combining red, green, and blue light in varying intensities—the so-called RGB additive primary colors. However, the relationship between the constituent amounts of red, green, and blue light and the resulting color is unintuitive, especially for inexperienced users, and for users familiar with subtractive color mixing of paints or traditional artists’ models based on tints and shades.
In an attempt to accommodate more traditional and intuitive color mixing models, computer graphics pioneers at
The following year, 1979, at SIGGRAPH, Tektronix introduced graphics terminals using HSL for color designation, and the Computer Graphics Standards Committee recommended it in their annual status report. These models were useful not only because they were more intuitive than raw RGB values, but also because the conversions to and from RGB were extremely fast to compute: they could run in real time on the hardware of the 1970s. Consequently, these models and similar ones have become ubiquitous throughout image editing and graphics software since then.
Munsell color system
Another influential older cylindrical color model is the early-20th-century Munsell color system. Albert Munsell began with a spherical arrangement in his 1905 book A Color Notation, but he wished to properly separate color-making attributes into separate dimensions, which he called hue, value, and chroma, and after taking careful measurements of perceptual responses, he realized that no symmetrical shape would do, so he reorganized his system into a lumpy blob.[18][19][A]
Munsell's system became extremely popular, the de facto reference for American color standards—used not only for specifying the color of paints and crayons, but also, e.g., electrical wire, beer, and soil color—because it was organized based on perceptual measurements, specified colors via an easily learned and systematic triple of numbers, because the color chips sold in the Munsell Book of Color covered a wide
Natural Color System
The Swedish Natural Color System (NCS), widely used in Europe, takes a similar approach to the Ostwald bicone at right. Because it attempts to fit color into a familiarly shaped solid based on "phenomenological" instead of photometric or psychological characteristics, it suffers from some of the same disadvantages as HSL and HSV: in particular, its lightness dimension differs from perceived lightness, because it forces colorful yellow, red, green, and blue into a plane.[24]
Preucil hue circle
In densitometry, a model quite similar to the hue defined above is used for describing colors of CMYK process inks. In 1953, Frank Preucil developed two geometric arrangements of hue, the "Preucil hue circle" and the "Preucil hue hexagon", analogous to our H and H2, respectively, but defined relative to idealized cyan, yellow, and magenta ink colors. The "Preucil hue error" of an ink indicates the difference in the "hue circle" between its color and the hue of the corresponding idealized ink color. The grayness of an ink is m/M, where m and M are the minimum and maximum among the amounts of idealized cyan, magenta, and yellow in a density measurement.[25]
CIELCHuv and CIELCHab
The
The HCL color space seems to be synonymous with CIELCH.
CIECAM02
The CIE's most recent model, CIECAM02 (CAM stands for "color appearance model"), is more theoretically sophisticated and computationally complex than earlier models. Its aims are to fix several of the problems with models such as CIELAB and CIELUV, and to explain not only responses in carefully controlled experimental environments, but also to model the color appearance of real-world scenes. Its dimensions J (lightness), C (chroma), and h (hue) define a polar-coordinate geometry.[20][24]
Color systems
There are various types of color systems that classify color and analyse their effects. The American
Other uses of "color model"
Models of mechanism of color vision
We also use "color model" to indicate a model or mechanism of color vision for explaining how color signals are processed from visual cones to ganglion cells. For simplicity, we call these models color mechanism models. The classical color mechanism models are Young–Helmholtz's trichromatic model and Hering's opponent-process model. Though these two theories were initially thought to be at odds, it later came to be understood that the mechanisms responsible for color opponency receive signals from the three types of cones and process them at a more complex level.[30] A widely accepted model is called the zone model. A symmetrical zone model compatible with the trichromatic theory, the opponent theory, and Smith's color transform model is called the decoding model [31]
Vertebrate evolution of color vision
Vertebrate animals were primitively
Human
See also
Notes
- Munsell Color Systemand its references.
- , and their references.
References
- ISBN 978-0500278185.
- ^ Chevreul, Michel Eugène (1861). The Laws of Contrast of Colour. London: Routledge, Warne, and Routledge. p. 25. – English translation by John Spanton
- ISBN 978-0520226111.
- ^ Le Blon, Jakob Christophe (1725). Coloritto; or the Harmony of Colouring in Painting: Reduced to Mechanical Practice under Easy Precepts, and Infallible Rules; Together with some Colour'd Figures. Retrieved July 4, 2020.
- S2CID 186212141. Retrieved July 4, 2020.
- ^ MacEvoy, Bruce (2005). "Color vision: Do "primary" colors exist?". Handprint.com. Retrieved September 1, 2017.
- ^ MS Sharon Ross, Elise Kinkead (2004). Decorative Painting & Faux Finishes. Creative Homeowner. ISBN 1-58011-179-3.
- ^ O. M. Lilien, Jacob Christoph Le Blon, 1667–1741: Inventor of Three- and Four-colour Printing. Stuttgart 1985
- ^ v=onepage&q=%22le%20blon%22%20color%20printing&f=false The Science of Color
- ^ David Briggs 2013, The Dimensions of Color 7.2 The RYB hu e circle or "artists' color wheel".
- ISBN 1-55860-792-7.
- ISBN 1-55622-354-4.
- ^ Crean, Buckley. "Device Independent Color—Who Wants It?" (PDF). SPIE. 2171: 267. Archived from the original (PDF) on February 4, 2023. Retrieved November 13, 2023.
- ISBN 0-442-24038-4.
- ^ Levkowitz and Herman (1993)
- ^ Smith (1978)
- ^ Joblove and Greenberg (1978)
- ^ Runge, Phillipp Otto (1810). Die Farben-Kugel, oder Construction des Verhaeltnisses aller Farben zueinander [The Color Sphere, or Construction of the Relationship of All Colors to Each Other] (in German). Hamburg, Germany: Perthes.
- ^ Albert Henry Munsell (1905). A Color Notation. Boston, MA: Munsell Color Company.
- ^ a b c Fairchild (2005)
- .
- S2CID 118953303.
- .
- ^ a b c MacEvoy (2010)
- ^ Frank Preucil (1953). "Color Hue and Ink Transfer—Their Relation to Perfect Reproduction". Proceedings of the 5th Annual Technical Meeting of TAGA. pp. 102–110.
- ^ Kuehni (2003)
- ISBN 0-86343-368-5.
- ^ "The Lab Color Mode in Photoshop". Adobe Systems. January 2007. Archived from the original on December 7, 2008.
- ISBN 978-0-08-052322-4.
- ^ Kandel ER, Schwartz JH and Jessell TM, 2000. Principles of Neural Science, 4th ed., McGraw-Hill, New York. pp. 577–80.
- ^ Lu C, 2021, Explaining colour vision with the decoding model, Research Features, Vol.135, pp.142-145.
Bibliography
- Fairchild, Mark D. (2005). Color Appearance Models (2nd ed.). Addison-Wesley. Archived from the original on October 19, 2013. Retrieved September 11, 2018. This book doesn't discuss HSL or HSV specifically, but is one of the most readable and precise resources about current color science.
- Joblove, George H.; Greenberg, Donald (August 1978). "Color spaces for computer graphics". . Joblove and Greenberg's paper was the first describing the HSL model, which it compares to HSV.
- Kuehni, Rolf G. (2003). Color Space and Its Divisions: Color Order from Antiquity to the present. New York: Wiley. ISBN 978-0-471-32670-0. This book only briefly mentions HSL and HSV, but is a comprehensive description of color order systems through history.
- Levkowitz, Haim; Herman, Gabor T. (1993). "GLHS: A Generalized Lightness, Hue and Saturation Color Model". . This paper explains how both HSL and HSV, as well as other similar models, can be thought of as specific variants of a more general "GLHS" model. Levkowitz and Herman provide pseudocode for converting from RGB to GLHS and back.
- MacEvoy, Bruce (January 2010). "Color Vision". handprint.com.. Especially the sections about "Modern Color Models" and "Modern Color Theory". MacEvoy's extensive site about color science and paint mixing is one of the best resources on the web. On this page, he explains the color-making attributes, and the general goals and history of color order systems—including HSL and HSV—and their practical relevance to painters.
- doi:10.1145/965139.807361. This is the original paper describing the "hexcone" model, HSV. Smith was a researcher at NYIT’s Computer Graphics Lab. He describes HSV's use in an early digital paintingprogram.
External links
- Illustrations and summaries of RGB, CMYK, LAB, HSV, HSL, and NCS
- Demonstrative color conversion applet
- HSV Colors by Hector Zenil, The Wolfram Demonstrations Project
- HSV to RGB by CodeBeautify