Initial Commit

node_modules/color-space/hsi.js

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+/**
+ * http://www.cse.usf.edu/~mshreve/rgb-to-hsi
+ * http://web.archive.org/web/20130124054245/http://web2.clarkson.edu/class/image_process/RGB_to_HSI.pdf
+ *
+ * @module color-space/hsl
+ */
+import rgb from './rgb.js';
+
+var hsi = {
+	name: 'hsi',
+	min: [0, 0, 0],
+	max: [360, 100, 255],
+	channel: ['hue', 'saturation', 'intensity'],
+	alias: ['HSI']
+};
+
+export default hsi
+
+
+/**
+ * HSI to RGB
+ *
+ * @param {Array<number>} hsi Channel values
+ *
+ * @return {Array<number>} RGB channel values
+ */
+hsi.rgb = function (hsi) {
+	var h = (hsi[0] < 0 ? (hsi[0] % 360) + 360 : (hsi[0] % 360)) * Math.PI / 180;
+	var s = Math.max(0, Math.min(hsi[1], 100)) / 100;
+	var i = Math.max(0, Math.min(hsi[2], 255)) / 255;
+
+	var pi3 = Math.PI / 3;
+
+	var r, g, b;
+	if (h < (2 * pi3)) {
+		b = i * (1 - s);
+		r = i * (1 + (s * Math.cos(h) / Math.cos(pi3 - h)));
+		g = i * (1 + (s * (1 - Math.cos(h) / Math.cos(pi3 - h))));
+	}
+	else if (h < (4 * pi3)) {
+		h = h - 2 * pi3;
+		r = i * (1 - s);
+		g = i * (1 + (s * Math.cos(h) / Math.cos(pi3 - h)));
+		b = i * (1 + (s * (1 - Math.cos(h) / Math.cos(pi3 - h))));
+	}
+	else {
+		h = h - 4 * pi3;
+		g = i * (1 - s);
+		b = i * (1 + (s * Math.cos(h) / Math.cos(pi3 - h)));
+		r = i * (1 + (s * (1 - Math.cos(h) / Math.cos(pi3 - h))));
+	}
+
+	return [r * 255, g * 255, b * 255];
+};
+
+
+/**
+ * RGB to HSI
+ *
+ * @param {Array<number>} rgb Channel values
+ *
+ * @return {Array<number>} HSI channel values
+ */
+rgb.hsi = function (rgb) {
+	var sum = rgb[0] + rgb[1] + rgb[2];
+
+	var r = rgb[0] / sum;
+	var g = rgb[1] / sum;
+	var b = rgb[2] / sum;
+
+	var h = Math.acos(
+		(0.5 * ((r - g) + (r - b))) /
+		Math.sqrt((r - g) * (r - g) + (r - b) * (g - b))
+	);
+	if (b > g) {
+		h = 2 * Math.PI - h;
+	}
+
+	var s = 1 - 3 * Math.min(r, g, b);
+
+	var i = sum / 3;
+
+	return [h * 180 / Math.PI, s * 100, i];
+};