Editing HSL and HSV (section)

{{short description|Alternative representations of the RGB color model}}

[[File:Hsl-hsv models.svg|thumb|upright=1.3|Fig. 1. HSL (a–d) and HSV (e–h). Above (a, e): cut-away three-dimensional models of each. Below: two-dimensional plots showing two of a model's three parameters at once, holding the other constant: cylindrical shells (b, f) of constant saturation, in this case the outside surface of each cylinder; horizontal cross-sections (c, g) of constant HSL lightness or HSV value, in this case the slices halfway down each cylinder; and rectangular vertical cross-sections (d, h) of constant hue, in this case of hues 0° red and its complement 180° cyan.]]

'''HSL''' and '''HSV''' are the two most common [[cylindrical coordinate system|cylindrical-coordinate]] representations of points in an [[RGB color model]]. The two representations rearrange the geometry of RGB in an attempt to be more intuitive and [[color vision|perceptually]] relevant than the [[cartesian coordinate system|cartesian]] (cube) representation. Developed in the 1970s for [[computer graphics]] applications, HSL and HSV are used today in [[color tool|color pickers]], in [[image editing]] software, and less commonly in [[image analysis]] and [[computer vision]].

HSL stands for ''hue'', ''saturation'', and ''lightness'', and is often also called '''HLS'''. HSV stands for ''hue'', ''saturation'', and ''value'', and is also often called '''HSB''' (''B'' for ''brightness''). A third model, common in computer vision applications, is '''HSI''', for ''hue'', ''saturation'', and ''intensity''. However, while typically consistent, these definitions are not standardized, and any of these abbreviations might be used for any of these three or several other related cylindrical models. (For technical definitions of these terms, see [[#Color-making attributes|below]].)

In each cylinder, the angle around the central vertical axis corresponds to "[[hue]]", the distance from the axis corresponds to "[[colorfulness|saturation]]", and the distance along the axis corresponds to "[[lightness]]", "value" or "[[brightness]]". Note that while "hue" in HSL and HSV refers to the same attribute, their definitions of "saturation" differ dramatically. Because HSL and HSV are simple transformations of device-dependent RGB models, the physical colors they define depend on the colors of the red, green, and blue [[primary color|primaries]] of the device or of the particular RGB space, and on the [[gamma correction]] used to represent the amounts of those primaries. Each unique RGB device therefore has unique HSL and HSV spaces to accompany it, and numerical HSL or HSV values describe a different color for each basis RGB space.<ref>See [[Absolute color space]].</ref>

Both of these representations are used widely in computer graphics, and one or the other of them is often more convenient than RGB, but both are also criticized for not adequately separating color-making attributes, or for their lack of perceptual uniformity. Other more computationally intensive models, such as [[CIELAB]] or [[CIECAM02]] are said to better achieve these goals.