spaces-jzazbz.md

J_za_zb_z color spaces

Jzazbz

• Type: JzazbzColor
• Channels:
  • J_z (lightness) usually between 0 and 1
  • a_z green-red chromaticity usually between -1 and 1
  • b_z blue-yellow chromaticity usually between -1 and 1

The J_za_zb_z (Safdar & al., 2017) is a novel color space designed for perceptual uniformity, high dynamic range, and wide gamut.

// red
var c1 = new JzazbzColor(0.6004, 0.1864, 0.1541);

// white (D65)
var c2 = new JzazbzColor(0.9886, -0.0002, -0.0001);

// gray (D65)
var c3 = new JzazbzColor(0.5446, -0.0002, -0.0001);

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

JzCzhz

• Type: JzCzhzColor
• Channels:
  • J_z (lightness) usually between 0 and 1
  • C_z (chroma) usually between 0 and 1
  • h_z (hue in degrees) between 0° and 360°

The J_zC_zh_z color space is a cylindrical representation of the J_za_zb_z color space.

// red
var c1 = new JzCzhzColor(0.6004, 0.2418, 39.58);

// white (D65)
var c2 = new JzCzhzColor(0.9886, 0.0003, 211.6);

// gray (D65)
var c3 = new JzCzhzColor(0.5446, 0.0003, 211.6);

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

Conversion strategy

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

Only exception is the JzCzhzColor where we go through JzazbzColor first.

The JzazbzColor 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.

In most cases, you'll want to use the D65 white point when operating in J_za_zb_z and J_zC_zh_z.

How to convert between Jzazbz and RGB?

In this example, the conversion from RGB color space to Jzazbz 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 rgbToJzazbz = new ConverterBuilder().FromRGB(rgbWorkingSpace).ToJzazbz(rgbWorkingSpace.WhitePoint).Build();
var outputJzazbz = rgbToJzazbz.Convert(inputRgb); // Jzazbz [Jz=0.6004, az=0.1864, bz=0.1541]

The reverse is similar:

var inputJzazbz = new JzazbzColor(0.6004, 0.1864, 0.1541);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

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

How to convert between JzCzhz and RGB?

Conversions between JzCzhz and RGB are similar to Jzazbz above.

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

var rgbToJzCzhz = new ConverterBuilder().FromRGB(rgbWorkingSpace).ToJzCzhz(rgbWorkingSpace.WhitePoint).Build();
var outputJzCzhz = rgbToJzCzhz.Convert(inputRgb); // JzCzhz [Jz=0.6004, Cz=0.2418, hz=39.58]

The reverse:

var inputJzCzhz = new JzCzhzColor(0.6004, 0.2418, 39.58);
var rgbWorkingSpace = RGBWorkingSpaces.sRGB;

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

J_zC_zh_z color difference

The J_zC_zh_z color space can also be used with the J_zC_zh_z Delta-E_z color difference algorithm.

Related links

• https://observablehq.com/@jrus/jzazbz
• Cylindrical color spaces