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XYZ color space

XYZ

  • Type: XYZColor
  • Channels:
    • X from 0 to 1
    • Y (Luminance) from 0 to 1
    • Z from 0 to 1

The CIE 1931 XYZ color space is one of the basic color spaces in Colourful. It's utilized for many applications. The white points of illuminants are specified in XYZ. It's also used in majority of conversions between color spaces, as most color spaces define conversion to/from XYZ. So when we convert between two color spaces, it's very likely we'll need to go through the XYZ color space as intermediate.

// red
var c1 = new XYZColor(0.3769, 0.2108, 0.0694);

// white (D65)
var c2 = new XYZColor(0.95047, 1, 1.08883);

// gray (D65)
var c3 = new XYZColor(0.2034, 0.2140, 0.2331);

// black
var c4 = new XYZColor(0, 0, 0);

xy and xyY

The CIE XYZ has an analogue xyY color space and xy chromaticity. Follow the link to the dedicated documentation page about these.

Note that the xy chromaticity isn't simply the X and Y channels of XYZ. Uppercase/lowercase X and Y mean something different.

Conversion strategy

Since XYZ is considered as the "base" space, it's actually the other color spaces define how to convert to XYZ.

White points and chromatic adaptation

Most of the time when talking about colors, you need to specify the reference white point. For more information about this, see the Illuminants and white points page.

How to convert between XYZ and RGB?

In this example, the conversion from RGB color space to XYZ is demonstrated. We use the sRGB working space and keep the D65 white point so no chromatic adaptation is needed.

var inputRgb = new RGBColor(0.937, 0.2, 0.251);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

var rgbToXyz = new ConverterBuilder().FromRGB(rgbWorkingSpace).ToXYZ(rgbWorkingSpace.WhitePoint).Build();
var outputXyz = rgbToXyz.Convert(inputRgb); // XYZ [X=0.38, Y=0.21, Z=0.07]

The reverse is similar:

var inputXyz = new XYZColor(0.3769, 0.2108, 0.0694);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

var xyzToRgb = new ConverterBuilder().FromXYZ(rgbWorkingSpace.WhitePoint).ToRGB(rgbWorkingSpace).Build();
var outputRgb = xyzToRgb.Convert(inputXyz); // RGB [R=0.94, G=0.2, B=0.25]

Related links