Editing HSL and HSV (section)

==Motivation==
{{see also|Color theory|RGB color model|RGB color space}}
{{multiple image
 | align   = right
 | image1  = tint-tone-shade.svg
 | width1  = 200
 | caption1 = Fig. 4. Painters long mixed colors by combining relatively bright pigments with black and white. Mixtures with white are called ''tints'', mixtures with black are called ''shades'', and mixtures with both are called ''tones''. See [[Tints and shades]].<ref name=Levkowitz>[[#Levkowitz|Levkowitz and Herman (1993)]]</ref>
 | alt1   =
 | image2  = Ostwald.svg
 | width2  = 200
 | caption2 = Fig. 5. This 1916 color model by German chemist [[Wilhelm Ostwald]] exemplifies the "mixtures with white and black" approach, organizing 24 "pure" colors into a [[color circle|hue circle]], and colors of each hue into a triangle. The model thus takes the shape of a bicone.<ref>Wilhelm Ostwald (1916). ''Die Farbenfibel''. Leipzig.</ref><ref>Wilhelm Ostwald (1918). ''Die Harmonie der Farben''. Leipzig.</ref>
 | alt2   = Several paint mixing terms can be arranged into a triangular arrangement: the left edge of the triangle shows ''white'' at its top and ''black'' at its bottom with ''gray'' between the two, each in its respective oval. A ''pure color'' (in this case, a bright blue-green) lies at the right corner of the triangle. On the edge between the pure color and black is a ''shade'' (a darker blue-green), between the pure color and white is a ''tint'' (a lighter, faded blue-green), and a ''tone'' lies in the middle of the triangle (a muted blue-green).
}}
{{multiple image
 | width   = 200
 | image1  = RGB Cube Show lowgamma cutout a.png
 | caption1 = Fig. 6a. The RGB gamut can be arranged in a cube.
 | alt1   = The RGB cube has black at its origin, and the three dimensions R, G, and B pointed in orthogonal directions away from black. The corner in each of those directions is the respective primary color (red, green, or blue), while the corners further away from black are combinations of two primaries (red plus green makes yellow, red plus blue makes magenta, green plus blue makes cyan). At the cube's corner farthest from the origin lies white. Any point in the cube describes a particular color within the gamut of RGB.
 | image2  = RGB Cube Show lowgamma cutout b.png
 | caption2 = Fig. 6b. The same image, with a portion removed for clarity.
 | alt2 = The same image, with a portion removed for clarity.
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 | image3  = RGB Cube Show lowgamma cutout c.png
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{{multiple image
 | align   = right
 | image3  = Tektronix-hsl-patent-diagram.png
 | width3  = 300
 | caption3 = Fig. 7. Tektronix graphics terminals used the earliest commercial implementation of HSL, in 1979. This diagram, from a patent filed in 1983, shows the bicone geometry underlying the model.<ref>{{cite patent |inventor1-given=Gar A. |inventor1-surname=Bergstedt |country=US |number=4694286 |url=http://www.google.com/patents/about?id=WA8xAAAAEBAJ |status=patent |title=Apparatus and method for modifying displayed color images |fdate=1983-04-08 |pubdate=1987-09-15 |assign1= Tektronix, Inc }}</ref>
 | alt3   = In classic patent application style, this is a black-and-white diagram with the patent name, inventor name, and patent number listed at the top, shaded by crosshatching. This diagram shows a three-dimensional view of Tektronix's biconic HSL geometry, made up of horizontal circular slices along a vertical axis expanded for ease of viewing. Within each circular slice, saturation goes from zero at the center to one at the margins, while hue is an angular dimension, beginning at blue with hue zero, through red with hue 120 degrees and green with hue 240 degrees, and back to blue.
}}

Most televisions, computer displays, and projectors produce colors by combining red, green, and blue light in varying intensities – the so-called [[RGB color model|RGB]] [[additive color|additive]] [[primary color]]s. The resulting mixtures in [[RGB color space]] can reproduce a wide variety of colors (called a [[gamut]]); 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 ({{nobr|fig. 4}}). Furthermore, neither additive nor subtractive color models define color relationships the same way the [[color vision|human eye]] does.{{refn|group=upper-alpha |For instance, a 1982 study by Berk, et al., found that users were better at describing colors in terms of HSL than RGB coordinates, after being taught both systems, but were much better still at describing them in terms of the natural-language CNS model (which uses names such as "very dark grayish yellow-green" or "medium strong bluish purple"). This shouldn't be taken as gospel however: a 1987 study by Schwarz, et al., found that users could match colors using RGB controls faster than with HSL controls; a 1999 study by Douglas and Kirkpatrick found that the visual feedback in the user interface mattered more than the particular color model in use, for user matching speed.<ref>{{cite journal|author1=Toby Berk |author2=Arie Kaufman |author3=Lee Brownston |date=August 1982 |title=A human factors study of color notation systems for computer graphics |journal=Communications of the ACM |volume=25 |issue=8 |pages=547–550 |doi=10.1145/358589.358606|s2cid=14838329 |doi-access=free }}</ref><ref>{{cite journal|author1=Michael W. Schwarz |author2=William B. Cowan |author3=John C. Beatty |date=April 1987 |title=An experimental comparison of RGB, YIQ, LAB, HSV, and opponent color models |journal=ACM Transactions on Graphics |volume=6 |issue=2 |pages=123–158 |doi=10.1145/31336.31338|s2cid=17287484 |doi-access=free }}</ref><ref>{{cite journal|author1=Sarah A. Douglas |author2=Arthur E. Kirkpatrick |date=April 1999 |title=Model and representation: the effect of visual feedback on human performance in a color picker interface |doi=10.1145/318009.318011 |journal=ACM Transactions on Graphics |volume=18 |issue=2 |pages= 96–127 |s2cid=14678328 |doi-access=free }}</ref>}}

For example, imagine we have an RGB display whose color is controlled by three [[slider (computing)|sliders]] ranging from {{nobr|0–255}}, one controlling the intensity of each of the red, green, and blue primaries. If we begin with a relatively colorful [[Orange (colour)|orange]] {{nobr|{{colorsample2|#D97621}}}}, with [[sRGB]] values {{nobr|1=''R'' = 217}}, {{nobr|1=''G'' = 118}}, {{nobr|1=''B'' = 33}}, and want to reduce its colorfulness by half to a less saturated orange {{nobr|{{colorsample2|#BA845C}}}}, we would need to drag the sliders to decrease ''R'' by 31, increase ''G'' by 24, and increase ''B'' by 59, as pictured below.

[[File:unintuitive-rgb.png|300px]]

Beginning in the 1950s, [[color television]] broadcasts used a [[Color television#Compatible color|compatible color]] system whereby "[[Luma (video)|luminance]]" and "[[chrominance]]" signals were encoded separately, so that existing unmodified black-and-white televisions could still receive color broadcasts and show a monochrome image.<ref>The original patent on this idea was by [[Georges Valensi]] in 1938: {{pb}} {{cite patent |country=FR |number=841335 |status=patent |title=Procédé de télévision en couleurs |fdate=1938-01-17 |gdate=1939-02-06 |pubdate=1939-05-17 |inventor1-surname=Valensi |inventor1-given=Georges}} {{pb}} {{cite patent |country=US |number=2375966 |status=patent |title=System of television in colors |fdate=1939-01-14 |pubdate=1945-05-15 |inventor1-surname=Valensi |inventor1-given=Georges}}</ref>

In an attempt to accommodate more traditional and intuitive color mixing models, computer graphics pioneers at [[PARC (company)|PARC]] and [[New York Institute of Technology|NYIT]] introduced the HSV model for computer display technology in the mid-1970s, formally described by [[Alvy Ray Smith]]<ref name=Smith>[[#Smith|Smith (1978)]]</ref> in the August 1978 issue of [[Computer Graphics (publication)|''Computer Graphics'']]. In the same issue, Joblove and Greenberg<ref name=Joblove>[[#Joblove|Joblove and Greenberg (1978)]]</ref> described the HSL model – whose dimensions they labeled ''hue'', ''relative chroma'', and ''intensity'' – and compared it to HSV ({{nobr|fig. 1}}). Their model was based more upon how colors are organized and conceptualized in [[color vision|human vision]] in terms of other color-making attributes, such as hue, lightness, and chroma; as well as upon traditional color mixing methods – e.g., in painting – that involve mixing brightly colored pigments with black or white to achieve lighter, darker, or less colorful colors.

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 ({{nobr|fig. 7}}). 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. Some of their uses are described [[#Use in end-user software|below]].<ref>[[Maureen C. Stone]] (August 2001). [http://graphics.stanford.edu/courses/cs448b-02-spring/04cdrom.pdf "A Survey of Color for Computer Graphics"]. Course at SIGGRAPH 2001.</ref><ref>{{cite journal|author=Ware Myers |date=July 1979|title=Interactive Computer Graphics: Flying High-Part I|journal=Computer|volume=12|issue=7|pages=8–17|doi=10.1109/MC.1979.1658808 |s2cid=15344162}}</ref><ref>{{cite journal|author1=N. Magnetat-Thalmann |author2=N. Chourot |author3=D. Thalmann |date=March 1984|title=Colour Gradation, Shading and Texture Using a Limited Terminal|doi=10.1111/j.1467-8659.1984.tb00092.x|journal=Computer Graphics Forum|volume=3|pages=83–90|s2cid=29541525 }}</ref><ref>{{cite journal|doi=10.1145/988497.988498|date= August 1979|last1=Computer Graphics Staff|title=Status report of the graphic standards planning committee |journal=ACM SIGGRAPH Computer Graphics|volume=13|issue=3|pages=1–10|s2cid=43687764}}</ref>

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