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rgb2hsv

Convert RGB colors to HSV

Syntax

hsv = rgb2hsv(rgb)

Description

example

hsv = rgb2hsv(rgb) converts RGB values to the appropriate hue, saturation, and value (HSV) coordinates. rgb can be a p-by-3 colormap array or an m-by-n-by-3 image array. hsv is the same size as rgb.

Examples

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Get a down-sampled version of the prism colormap.

rgb = prism(6)
rgb = 

    1.0000         0         0
    1.0000    0.5000         0
    1.0000    1.0000         0
         0    1.0000         0
         0         0    1.0000
    0.6667         0    1.0000

Convert the RGB values in the colormap to HSV.

hsv = rgb2hsv(rgb)
hsv = 

         0    1.0000    1.0000
    0.0833    1.0000    1.0000
    0.1667    1.0000    1.0000
    0.3333    1.0000    1.0000
    0.6667    1.0000    1.0000
    0.7778    1.0000    1.0000

Create a 2-by-2 truecolor image.

rgb(:,:,1) = [1 1; 0 .5];
rgb(:,:,2) = [0 1; 0 .5];
rgb(:,:,3) = [0 0; 1 .5];
image(rgb);

Convert the image to an HSV array.

hsv = rgb2hsv(rgb)
hsv = 
hsv(:,:,1) =

         0    0.1667
    0.6667         0


hsv(:,:,2) =

     1     1
     1     0


hsv(:,:,3) =

    1.0000    1.0000
    1.0000    0.5000

Input Arguments

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RGB values to convert, specified as a p-by-3 array or an m-by-n-by-3 image array.

If rgb is a p-by-3 array, then it must be of type double, and each row must contain an RGB triplet. An RGB triplet is a three-element row vector whose values specify the red, green, and blue components of a color, respectively. The values must be in the range [0, 1].

If rgb is an m-by-n-by-3 image array, then it can be of type double, single, uint8, or uint16. The third dimension of the array specifies the red, green, or blue intensity at pixel (i,j):

  • rgb(i,j,1) specifies the red intensity.

  • rgb(i,j,2) specifies the green intensity.

  • rgb(i,j,3) specifies the blue intensity.

Data Types: single | double | uint8 | uint16

Output Arguments

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HSV values, returned as returned as an array that is the same size as rgb: a p-by-3 array or an m-by-n-by-3 array. The values are in the range [0, 1], and their type depends on the type of rgb:

  • If rgb is of type single, then hsv is of type single.

  • Otherwise, hsv is of type double.

The attributes (hue, saturation, and value) are described in the following table.

AttributeDescription Location in hsv Array
HueValue from 0 to 1 that corresponds to the color’s position on a color wheel. As hue increases from 0 to 1, the color transitions from red to orange, yellow, green, cyan, blue, magenta, and finally back to red.
  • hsv(:,1) when hsv is p-by-3

  • hsv(:,:,1) when hsv is m-by-n-by-3

SaturationAmount of hue or departure from neutral. 0 indicates a neutral shade, whereas 1 indicates maximum saturation.
  • hsv(:,2) when hsv is p-by-3

  • hsv(:,:,2) when hsv is m-by-n-by-3

Value

Maximum value among the red, green, and blue components of a specific color.

  • hsv(:,3) when hsv is p-by-3

  • hsv(:,:,3) when hsv is m-by-n-by-3

References

[1] Smith, A. R. “Color Gamut Transform Pairs”. SIGGRAPH 78 Conference Proceedings. 1978, pp. 12–19.

See Also

Introduced before R2006a

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