Initial Commit

node_modules/color-space/jpeg.js

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+/**
+ * https://en.wikipedia.org/wiki/YCbCr#JPEG_conversion
+ *
+ * JPEG conversion without head/footroom
+ *
+ * @module  color-space/jpeg
+ */
+import rgb from './rgb.js';
+
+
+var jpeg = {
+	name: 'jpeg',
+	min: [0, 0, 0],
+	max: [255, 255, 255],
+	channel: ['Y', 'Cb', 'Cr'],
+	alias: ['JPEG']
+};
+
+export default (jpeg);
+
+
+/**
+ * JPEG to RGB
+ * transform through analog form
+ *
+ * @param {Array<number>} arr RGB values
+ *
+ * @return {Array<number>} JPEG values
+ */
+jpeg.rgb = function (arr) {
+	var y = arr[0], cb = arr[1], cr = arr[2];
+
+	return [
+		y + 1.402 * (cr - 128),
+		y - 0.34414 * (cb - 128) - 0.71414 * (cr - 128),
+		y + 1.772 * (cb - 128)
+	]
+};
+
+
+/**
+ * RGB to JPEG
+ * transform through analog form
+ *
+ * @param {Array<number>} arr JPEG values
+ *
+ * @return {Array<number>} RGB values
+ */
+rgb.jpeg = function (arr) {
+	var r = arr[0], g = arr[1], b = arr[2];
+
+	return [
+		0.299 * r + 0.587 * g + 0.114 * b,
+		128 - 0.168736 * r - 0.331264 * g + 0.5 * b,
+		128 + 0.5 * r - 0.418688 * g - 0.081312 * b
+	]
+};