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Luv color spaces

Luv

  • Type: LuvColor
  • Channels:
    • L* (lightness) usually between 0% and 100%
    • u* chromaticity mostly between -100% and 100% (not always)
    • v* chromaticity mostly between -100% and 100% (not always)

The CIE L*u*v* (1976) (CIELUV) color space (similarly to CIELAB) is designed to have perceptual uniformity, which means that distances in the color space should more closely correspond to how humans perceive the color differences.

// red
var c1 = new LuvColor(53.04, 140.97, 26.21);

// white
var c2 = new LuvColor(100, 0, 0);

// gray
var c3 = new LuvColor(53.39, 0, 0);

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

LChuv

  • Type: LChuvColor
  • Channels:
    • L* (lightness) usually between 0% and 100%
    • C* (chroma) usually between 0% and 100%
    • h° (hue in degrees) between 0° and 360°

The CIE L*C*h°uv (CIELCH) color space is a cylindrical representation of the Luv color space. Sometimes it's also known as CIE HLCuv.

// red
var c1 = new LChuvColor(53.04, 143.39, 10.53);

// white
var c2 = new LChuvColor(100, 0, 0);

// gray
var c3 = new LChuvColor(53.39, 0, 0);

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

Conversion strategy

When converting between LuvColor and any other color space, it always goes through XYZColor first.

Only exception is the LChuvColor where we go through LuvColor first.

The LuvColor values are relative to the white point used. Which means that when converting between color spaces, you'll need to specify which white point you want the source/target color to be relative to. In case the white points in source and target are different, chromatic adaptation will be performed.

How to convert between Luv and RGB?

In this example, the conversion from RGB color space to Luv is demonstrated. We use the sRGB working space and keep the D65 white point.

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

var rgbToLuv = new ConverterBuilder().FromRGB(rgbWorkingSpace).ToLuv(rgbWorkingSpace.WhitePoint).Build();
var outputLuv = rgbToLuv.Convert(inputRgb); // Luv [L=53.04, u=140.97, v=26.21]

The reverse is similar:

var inputLuv = new LuvColor(53.04, 140.97, 26.21);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

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

How to convert between LChuv and RGB?

Conversions between LChuv and RGB are similar to Luv above.

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

var rgbToLChuv = new ConverterBuilder().FromRGB(rgbWorkingSpace).ToLChuv(rgbWorkingSpace.WhitePoint).Build();
var outputLChuv = rgbToLChuv.Convert(inputRgb); // LChuv [L=53.04, C=143.39, h=10.53]

The reverse:

var inputLChuv = new LChuvColor(53.04, 143.39, 10.53);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

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

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