Initial Commit

node_modules/color-space/ypbpr.js

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+/**
+ * https://en.wikipedia.org/?title=YPbPr
+ *
+ * YPbPr is analog form of YCbCr
+ * hence limits are [0..1]
+ *
+ * Default conversion is ITU-R BT.709
+ *
+ * @module  color-space/ypbpr
+ */
+import rgb from './rgb.js';
+
+var ypbpr = ({
+	name: 'ypbpr',
+	min: [0, -0.5, -0.5],
+	max: [1, 0.5, 0.5],
+	channel: ['Y', 'Pb', 'Pr'],
+	alias: ['YPbPr', 'Y/PB/PR', 'YPRPB', 'PRPBY', 'PBPRY', 'Y/Pb/Pr', 'YPrPb', 'PrPbY', 'PbPrY', 'Y/R-Y/B-Y', 'Y(R-Y)(B-Y)', 'R-Y', 'B-Y']
+});
+
+
+/**
+ * YPbPr to RGB
+ *
+ * @param {Array<number>} ypbpr RGB values
+ * @param {number} kb
+ * @param {number} kr
+ * @return {Array<number>} YPbPr values
+ */
+ypbpr.rgb = function (ypbpr, kb, kr) {
+	var y = ypbpr[0], pb = ypbpr[1], pr = ypbpr[2];
+
+	//default conversion is ITU-R BT.709
+	kb = kb || 0.0722;
+	kr = kr || 0.2126;
+
+	var r = y + 2 * pr * (1 - kr);
+	var b = y + 2 * pb * (1 - kb);
+	var g = (y - kr * r - kb * b) / (1 - kr - kb);
+
+	return [r * 255, g * 255, b * 255];
+};
+
+
+/**
+ * RGB to YPbPr
+ *
+ * @param {Array<number>} rgb YPbPr values
+ * @param {number} kb
+ * @param {number} kr
+ * @return {Array<number>} RGB values
+ */
+rgb.ypbpr = function (rgb, kb, kr) {
+	var r = rgb[0] / 255, g = rgb[1] / 255, b = rgb[2] / 255;
+
+	//ITU-R BT.709
+	kb = kb || 0.0722;
+	kr = kr || 0.2126;
+
+	var y = kr * r + (1 - kr - kb) * g + kb * b;
+	var pb = 0.5 * (b - y) / (1 - kb);
+	var pr = 0.5 * (r - y) / (1 - kr);
+
+	return [y, pb, pr];
+};
+
+
+export default ypbpr;