xyz.js

/**
 * CIE XYZ
 *
 * @module  color-space/xyz
 */
import rgb from './rgb.js';

const xyz = {
	name: 'xyz',
	min: [0, 0, 0],
	channel: ['X', 'Y', 'Z'],
	alias: ['XYZ', 'ciexyz', 'cie1931'],

	// Whitepoint reference values with observer/illuminant
	// http://en.wikipedia.org/wiki/Standard_illuminant
	whitepoint: {
		//1931 2°
		2: {
			//incadescent
			A: [109.85, 100, 35.585],
			// B:[],
			C: [98.074, 100, 118.232],
			D50: [96.422, 100, 82.521],
			D55: [95.682, 100, 92.149],
			//daylight
			D65: [95.045592705167, 100, 108.9057750759878],
			D75: [94.972, 100, 122.638],
			//flourescent
			// F1: [],
			F2: [99.187, 100, 67.395],
			// F3: [],
			// F4: [],
			// F5: [],
			// F6:[],
			F7: [95.044, 100, 108.755],
			// F8: [],
			// F9: [],
			// F10: [],
			F11: [100.966, 100, 64.370],
			// F12: [],
			E: [100, 100, 100]
		},

		//1964  10°
		10: {
			//incadescent
			A: [111.144, 100, 35.200],
			C: [97.285, 100, 116.145],
			D50: [96.720, 100, 81.427],
			D55: [95.799, 100, 90.926],
			//daylight
			D65: [94.811, 100, 107.304],
			D75: [94.416, 100, 120.641],
			//flourescent
			F2: [103.280, 100, 69.026],
			F7: [95.792, 100, 107.687],
			F11: [103.866, 100, 65.627],
			E: [100, 100, 100]
		}
	}
};


/**
 * Top values are the whitepoint’s top values, default are D65
 */
xyz.max = xyz.whitepoint[2].D65;


/**
 * Transform xyz to rgb
 *
 * @param {Array<number>} _xyz Array of xyz values
 * @param {Array<number>} white Whitepoint reference
 * @return {Array<number>} RGB values
 */
xyz.rgb = function (_xyz, white) {
	// FIXME: make sure we have to divide like this. Probably we have to replace matrix as well then
	white = white || xyz.whitepoint[2].E;

	var x = _xyz[0] / white[0],
		y = _xyz[1] / white[1],
		z = _xyz[2] / white[2],
		r, g, b;

	// assume sRGB
	// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
	r = (x * 3.240969941904521) + (y * -1.537383177570093) + (z * -0.498610760293);
	g = (x * -0.96924363628087) + (y * 1.87596750150772) + (z * 0.041555057407175);
	b = (x * 0.055630079696993) + (y * -0.20397695888897) + (z * 1.056971514242878);

	r = r > 0.0031308 ? ((1.055 * Math.pow(r, 1.0 / 2.4)) - 0.055)
		: r = (r * 12.92);

	g = g > 0.0031308 ? ((1.055 * Math.pow(g, 1.0 / 2.4)) - 0.055)
		: g = (g * 12.92);

	b = b > 0.0031308 ? ((1.055 * Math.pow(b, 1.0 / 2.4)) - 0.055)
		: b = (b * 12.92);

	r = Math.min(Math.max(0, r), 1);
	g = Math.min(Math.max(0, g), 1);
	b = Math.min(Math.max(0, b), 1);

	return [r * 255, g * 255, b * 255];
}



/**
 * RGB to XYZ
 *
 * @param {Array<number>} rgb RGB channels
 *
 * @return {Array<number>} XYZ channels
 */
rgb.xyz = function (rgb, white) {
	var r = rgb[0] / 255,
		g = rgb[1] / 255,
		b = rgb[2] / 255;

	// assume sRGB
	r = r > 0.04045 ? Math.pow(((r + 0.055) / 1.055), 2.4) : (r / 12.92);
	g = g > 0.04045 ? Math.pow(((g + 0.055) / 1.055), 2.4) : (g / 12.92);
	b = b > 0.04045 ? Math.pow(((b + 0.055) / 1.055), 2.4) : (b / 12.92);

	var x = (r * 0.41239079926595) + (g * 0.35758433938387) + (b * 0.18048078840183);
	var y = (r * 0.21263900587151) + (g * 0.71516867876775) + (b * 0.072192315360733);
	var z = (r * 0.019330818715591) + (g * 0.11919477979462) + (b * 0.95053215224966);

	white = white || xyz.whitepoint[2].E;

	return [x * white[0], y * white[1], z * white[2]];
};



export default xyz;