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Encyclopedia > HSV color space

The HSV (Hue, Saturation, Value) model, also known as HSB (Hue, Saturation, Brightness), defines a color space in terms of three constituent components: A comparison of RGB and CMYK color spaces. ...

• Hue, the color type (such as red, blue, or yellow):
• Ranges from 0-360 (but normalized to 0-100% in some applications)
• Saturation, the "vibrancy" of the color:
• Ranges from 0-100%
• Also sometimes called the "purity" by analogy to the colorimetric quantities excitation purity and colorimetric purity
• The lower the saturation of a color, the more "grayness" is present and the more faded the color will appear, thus useful to define desaturation as the qualitative inverse of saturation
• Value, the brightness of the color:
• Ranges from 0-100%

The HSV model was created in 1978 by Alvy Ray Smith. It is a nonlinear transformation of the RGB color space, and may be used in color progressions. Note that HSV and HSB are the same, but HSL is different. An image with the hue altered The hue of this Painted Bunting is adjusted over the spectrum. ... Color is an important part of the visual arts. ... It has been suggested that this article or section be merged with Chromaticity. ... Colorimetry is the science that describes colors in numbers, or provides a physical color match using a variety of measurement instruments. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ... Brightness is an attribute of visual perception in which a source appears to emit a given amount of light. ... Alvy Ray Smith III (born 1943) is a noted pioneer in computer graphics. ... In mathematics, nonlinear systems represent systems whose behavior is not expressible as a sum of the behaviors of its descriptors. ... In mathematics, a transformation in elementary terms is any of a variety of different operations from geometry, such as rotations, reflections and translations. ... An RGB color space is any additive color space based on the RGB color model. ... Color progressions are ranges of color whose values transition smoothly through a hue, saturation, luminance, or any combination of the three. ... The HSL color space, also called HLS or HSI, stands for Hue, Saturation, Lightness (also Luminance or Luminosity) / Intensity. ...

## Contents

An HSV color wheel allows the user to quickly select a multitude of colors.
Time-varied representation of the HSV color wheel.

The HSV model is commonly used in computer graphics applications. In various application contexts, a user must choose a color to be applied to a particular graphical element. When used in this way, the HSV color wheel is often used. In it, the hue is represented by a circular region; a separate triangular region may be used to represent saturation and value. Typically, the vertical axis of the triangle indicates saturation, while the horizontal axis corresponds to value. In this way, a color can be chosen by first picking the hue from the circular region, then selecting the desired saturation and value from the triangular region. Image File history File links Download high-resolution version (1280x1024, 140 KB) Summary Image created by (3ucky(3all using Borland Delphi 2006, Adobe Photoshop 9. ... Image File history File links Download high-resolution version (1280x1024, 140 KB) Summary Image created by (3ucky(3all using Borland Delphi 2006, Adobe Photoshop 9. ... Image File history File links HSV_clr_wheel. ... Image File history File links HSV_clr_wheel. ... A graphics program is a piece of computer software that enables a user to modify or view graphics files. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ...

The conical representation of the HSV model is well-suited to visualizing the entire HSV color space in a single object.
Time-varied representation of the HSV cone.

The cylindrical representaion of the HSV model might be considered the most mathematically accurate model of the HSV color space.
Time-varied representation of the HSV cylinder.

## HSV and color perception

An image, along with its H, S and V components. Note that the H element is the only one displaying colour. Compare the dark on the left side of the barn roof and the white of the snow; in both cases these have colour, but the saturation is very low, causing them to be near-greyscale; the intensity of the barn, however, is much lower than the snow. The green of the grass is highly saturated and of moderate intensity; the blue of the mountains is consistent in colour but varies in intensity and saturation; and the sky has constant colour and intensity but varying saturation.

Artists sometimes prefer to use the HSV color model over alternative models such as RGB or CMYK, because of its similarities to the way humans tend to perceive color. RGB and CMYK are additive and subtractive models, respectively, defining color in terms of the combination of primaries, whereas HSV encapsulates information about a color in terms that are more familiar to humans: What color is it? How vibrant is it? How light or dark is it? The HLS color space is similar and arguably even better than HSV in this respect. Image File history File links Download high-resolution version (800x2392, 360 KB) Summary This takes an image ( Image:Barns grand tetons. ... Image File history File links Download high-resolution version (800x2392, 360 KB) Summary This takes an image ( Image:Barns grand tetons. ... The RGB color model utilizes the additive model in which red, green, and blue light are combined in various ways to create other colors. ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ... An additive color system involves light emitted directly from a source or illuminant of some sort. ... Subtractive color explains the theory of mixing paints, dyes, inks, and natural colorants to create colors which absorb some wavelengths of light and reflect others. ... A primary color or colour is a color that cannot be created by mixing other colors in the gamut of a given color space. ... The HLS color space, also called HSL or HSI, stands for Hue, Saturation, Lightness (also Luminance or Luminosity) / Intensity. ...

The HSV tristimulus space does not technically support a one-to-one mapping to physical power spectra as measured in radiometry. Thus it is not generally advisable to try to make direct comparisons between HSV coordinates and physical light properties such as wavelength or amplitude. However, if physical intuitions are indispensable, it is possible to translate HSV coordinates into pseudo-physical properties using the psychophysical terminology of colorimetry as follows: The power spectrum is a plot of the portion of a signals power (energy per unit time) falling within given frequency bins. ... In telecommunication and physics, radiometry is the science of radiation measurement. ... The wavelength is the distance between repeating units of a wave pattern. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... Colorimetry is the science that describes colors in numbers, or provides a physical color match using a variety of measurement instruments. ...

• Hue specifies the dominant wavelength of the color, except in the range between red and indigo (somewhere between 240 and 360 degrees) where the Hue denotes a position along the line of pure purples
• If the hue perception were recreated, actually using a monochromatic, pure spectral color at the dominant wavelength, the desaturation would be roughly analogous to an applied frequency spread around the dominant wavelength or alternatively the amount of equal-power (i.e. white) light added to the pure spectral color.
• The value is roughly analogous to the total power of the spectrum, or the maximum amplitude of the light waveform. However, it should be obvious from the equations below that value is actually closer to the power of the greatest spectral component (the statistical mode, not the cumulative power across the distribution.)

Dominant/complementary wavelength example on the CIE color space The x marks the color in question. ... Purple is any of a group of colors intermediate between deep blue and red. ... Color is an important part of the visual arts. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... Mode has several meanings: In statistics, the mode is the value that has the largest number of observations, namely the most frequent value or values. ...

## Transformation between HSV and RGB

An illustration of the relationship between HSV and RGB color spaces.
 $H in$ $left[ 0, 360 right]$ $S, V, R, G, B in$ $left[ 0, 1 right]$

From RGB to HSV: Image File history File links HSV-RGB-comparison. ... Image File history File links HSV-RGB-comparison. ...

Let MAX equal the maximum of the (R, G, B) values, and MIN equal the minimum of those values.

$H = begin{cases} mbox{undefined}, & mbox{if } MAX = MIN 60 times frac{G - B}{MAX - MIN} + 0, & mbox{if } MAX = R &mbox{and } G ge B 60 times frac{G - B}{MAX - MIN} + 360, & mbox{if } MAX = R &mbox{and } G < B 60 times frac{B - R}{MAX - MIN} + 120, & mbox{if } MAX = G 60 times frac{R - G}{MAX - MIN} + 240, & mbox{if } MAX = B end{cases}$

$S = begin{cases} 0, & mbox{if } MAX = 0 1 - frac {MIN} {MAX}, & mbox{otherwise} end{cases}$

$V = MAX ,$

From HSV to RGB:

 Hi = $leftlfloor { H over 60 } rightrfloormod 6$ f = ${ H over 60 } - H_i$ p = $V ( 1 - S ) ,$ q = $V ( 1 - f S ) ,$ t = $V ( 1 - ( 1 - f ) S ) ,$
 $mbox{if } H_i = 0 rightarrow$ R = V, G = t, B = p $mbox{if } H_i = 1 rightarrow$ R = q, G = V, B = p $mbox{if } H_i = 2 rightarrow$ R = p, G = V, B = t $mbox{if } H_i = 3 rightarrow$ R = p, G = q, B = V $mbox{if } H_i = 4 rightarrow$ R = t, G = p, B = V $mbox{if } H_i = 5 rightarrow$ R = V, G = p, B = q

In computer graphics, it is typical to represent each channel as an integer from 0 to 255 instead of a real number from 0 to 1. It is worth noting that when encoded in this way, every possible HSV color has an RGB equivalent. However, the inverse is not true. Certain RGB colors have no integer HSV representation. In fact, only 1/256th of the RGB colors are 'available' in HSV, effectively eliminating a single channel of control from the graphics artist.

## Complementary colors

Main article: Complementary color

We regard two colors as complementary if when mixed together they produce a shade of grey. Given a color (H, S, V) in HSV color space, there exists a complement (H', S', V') such that when (H, S, V) and (H', S', V') are mixed in equal proportions, the saturation of the resulting color is 0. Then, Complementary colors are pairs of colors that are in some way opposites of each other. ...

 H' = $begin{cases}H - 180, & mbox{if } H ge 180 H + 180, & mbox{if } H < 180 end{cases}$ S' = ${VS over V(S - 1) + 1}$ V' = V(S − 1) + 1

## References

• Rafael Gonzalez, Richard E. Woods (2002) Digital Image Processing, 2 ed, Prentice Hall Press. p. 295, ISBN 0-201-18075-8

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