Initial Commit

node_modules/color-space/tsl.js

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+/**
+ * https://en.wikipedia.org/wiki/TSL_color_space
+ * http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.86.6037&rep=rep1&type=pdf
+ *
+ * Tint, Saturation, Lightness
+ *
+ * @module  color-space/tsl
+ */
+import rgb from './rgb.js';
+
+var tsl = {
+	name: 'tsl',
+	min: [0, 0, 0],
+	max: [1, 1, 1],
+	channel: ['tint', 'saturation', 'lightness'],
+	alias: ['TSL'],
+};
+
+export default (tsl);
+
+/**
+ * TSL to RGB
+ *
+ * @param {Array<number>} tsl RGB values
+ *
+ * @return {Array<number>} TSL values
+ */
+tsl.rgb = function (tsl) {
+	var T = tsl[0],
+		S = tsl[1],
+		L = tsl[2];
+
+	//wikipedia solution
+	/*
+	// var x = - 1 / Math.tan(Math.PI * 2 * T);
+	var x = -Math.sin(2*Math.PI*T);
+	if ( x != 0 ) x = Math.cos(2*Math.PI*T)/x;
+
+	var g = T > .5 ? -S * Math.sqrt( 5 / (9 * (x*x + 1)) ) :
+			T < .5 ? S * Math.sqrt( 5 / (9 * (x*x + 1)) ) : 0;
+	var r = T === 0 ? 0.7453559 * S : (x * g + 1/3);
+
+	var R = k * r, G = k * g, B = k * (1 - r - g);
+	*/
+
+	var x = Math.tan(2 * Math.PI * (T - 1 / 4));
+	x *= x;
+
+	var r = Math.sqrt(5 * S * S / (9 * (1 / x + 1))) + 1 / 3;
+	var g = Math.sqrt(5 * S * S / (9 * (x + 1))) + 1 / 3;
+
+	var k = L / (.185 * r + .473 * g + .114);
+
+	var B = k * (1 - r - g);
+	var G = k * g;
+	var R = k * r;
+
+	return [
+		R * 255, G * 255, B * 255
+	];
+};
+
+
+/**
+ * RGB to TSL
+ *
+ * @param {Array<number>} rgb TSL values
+ *
+ * @return {Array<number>} RGB values
+ */
+rgb.tsl = function (rgb) {
+	var [r, g, b] = rgb;
+
+	var r_ = (r / (r + g + b) || 0) - 1 / 3,
+		g_ = (g / (r + g + b) || 0) - 1 / 3,
+		T = g_ != 0 ? 0.5 - Math.atan2(g_, r_) / 2 / Math.PI : 0,
+		S = Math.sqrt(9 / 5 * (r_ * r_ + g_ * g_)),
+		L = ((r * 0.299) + (g * 0.587) + (b * 0.114)) / 255;
+
+	return [T, S, L];
+};