Color

Color space conversions, support for International Color Consortium (ICC) profiles

The toolbox represents colors as RGB values, but there are other models besides RGB for representing colors numerically. The various color spaces exist because they present color information in ways that make certain calculations more convenient or because they provide a more intuitive way to identify colors. The toolbox provides functions for converting color data from one color space to another. The toolbox also supports International Color Consortium (ICC) profiles for describing colors.

Functions

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Color Space Conversion

`rgb2hsv`	Convert RGB colors to HSV
`rgb2lab`	Convert RGB to CIE 1976 Lab*
`rgb2ntsc`	Convert RGB color values to NTSC color space
`rgb2xyz`	Convert RGB to CIE 1931 XYZ
`rgb2ycbcr`	Convert RGB color values to YCbCr color space
`hsv2rgb`	Convert HSV colors to RGB
`lab2rgb`	Convert CIE 1976 Lab* to RGB
`lab2xyz`	Convert CIE 1976 Lab* to CIE 1931 XYZ
`ntsc2rgb`	Convert NTSC values to RGB color space
`xyz2lab`	Convert CIE 1931 XYZ to CIE 1976 Lab*
`xyz2rgb`	Convert CIE 1931 XYZ to RGB
`ycbcr2rgb`	Convert YCbCr color values to RGB color space
`colorcloud`	Display 3-D color gamut as point cloud in specified color space

Color Values to Data Type Conversion

`lab2double`	Convert Lab* color values to double
`lab2uint16`	Convert Lab color values to uint16
`lab2uint8`	Convert Lab color values to uint8
`xyz2double`	Convert XYZ color values to double
`xyz2uint16`	Convert XYZ color values to uint16

International Color Consortium (ICC) Profile

`iccfind`	Find ICC profiles
`iccread`	Read ICC profile
`iccroot`	Find system default ICC profile repository
`iccwrite`	Write ICC color profile data
`isicc`	Check for valid ICC profile data

Color Transformation

`makecform`	Create color transformation structure
`applycform`	Apply device-independent color space transformation
`imapprox`	Approximate indexed image by reducing number of colors

Automatic White Balance

`chromadapt`	Adjust color balance of RGB image with chromatic adaptation
`colorangle`	Angle between two RGB vectors
`illumgray`	Estimate illuminant using gray world algorithm
`illumpca`	Estimate illuminant using principal component analysis (PCA)
`illumwhite`	Estimate illuminant using White Patch Retinex algorithm
`lin2rgb`	Apply gamma correction to linear RGB values
`rgb2lin`	Linearize gamma-corrected RGB values
`whitepoint`	XYZ color values of standard illuminants

Topics

Understanding Color Spaces and Color Space Conversion

A color space maps a color in a multidimensional coordinate system. Color spaces have different advantages in identifying colors or performing calculations.

Device-Independent Color Spaces

Device-independent color spaces define a standardized color space where three values represent a color. Different standards exist for many applications of color display.

Profile-Based Color Space Conversions

Device profiles contain information about how input, output, and display devices reproduce colors. Convert the color space so displayed colors look the same across all devices.

Display Colors

The bit depth of a screen display defines how many distinct colors the display can produce. You can determine and change the screen bit depth of your system.

Reduce the Number of Colors in an Image

Learn how to reduce the number of colors in an image using color approximation or dithering.

Featured Examples

Comparison of Auto White Balance Algorithms

Our eyes are very good at judging what is white under different lighting conditions. Digital cameras, however, without some kind of adjustment, can easily capture unrealistic images with a strong color cast. Automatic white balance (AWB) algorithms try to correct for the ambient light with minimum input from the user, so that the resulting image looks like what our eyes would see. But which is the best AWB algorithm to use? In this example, we explain the process behind auto white balance and show how to compare and select the best algorithm.

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