rgb2hsv

Convert RGB colors to HSV

Syntax

HSV = rgb2hsv(RGB)

hsvmap = rgb2hsv(rgbmap)

Description

HSV = rgb2hsv(RGB) converts the red, green, and blue values of an RGB image to hue, saturation, and value (HSV) values of an HSV image.

hsvmap = rgb2hsv(rgbmap) converts an RGB colormap to an HSV colormap.

Examples

Convert Colormap to HSV

Get a down-sampled version of the prism colormap.

rgb = prism(6)

rgb = 6×3

    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 = 6×3

         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

Convert Truecolor Image to HSV

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

RGB — RGB image

m-by-n-by-3 numeric array

RGB image to convert, specified as an m-by-n-by-3 numeric array. The third dimension of RGB defines the red, green, and blue intensity of each pixel, respectively.

Data Types: single | double | uint8 | uint16

rgbmap — RGB colormap

c-by-3 numeric matrix

RGB colormap, specified as a c-by-3 numeric matrix with values in the range [0, 1]. Each row of rgbmap is a three-element RGB triplet that specifies the red, green, and blue components of a single color of the colormap.

Data Types: double

Output Arguments

HSV — HSV image

m-by-n-by-3 numeric array

HSV image, returned as an m-by-n-by-3 numeric array with values in the range [0, 1]. The third dimension of HSV defines the hue, saturation, and value for each pixel, respectively, as described in the table.

Attribute	Description
Hue	Value 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.
Saturation	Amount of hue or departure from neutral. 0 indicates a neutral shade, whereas 1 indicates maximum saturation.
Value	Maximum value among the red, green, and blue components of a specific color.

The data type of HSV depends on the type of RGB:

• If RGB is of type single, then HSV is of type single.

• Otherwise, HSV is of type double.

Data Types: double | single

hsvmap — HSV colormap

c-by-3 numeric matrix

HSV colormap, returned as a c-by-3 numeric matrix with values in the range [0, 1]. Each row of hsvmap is a three-element HSV triplet that specifies the hue, saturation, and value components of a single color of the colormap.

The data type depends on the type of rgbmap:

• If rgbmap is of type single, then hsvmap is of type single.

• Otherwise, hsvmap is of type double.

Data Types: single | double

References

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

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).