First Commit

node_modules/culori/src/cubehelix/convertRgbToCubehelix.js

@@ -0,0 +1,40 @@
+/*
+	Convert a RGB color to the Cubehelix HSL color space.
+
+	This computation is not present in Green's paper:
+	https://arxiv.org/pdf/1108.5083.pdf
+
+	...but can be derived from the inverse, HSL to RGB conversion.
+
+	It matches the math in Mike Bostock's D3 implementation:
+
+	https://github.com/d3/d3-color/blob/master/src/cubehelix.js
+ */
+
+import { radToDeg, M } from './constants.js';
+
+let DE = M[3] * M[4];
+let BE = M[1] * M[4];
+let BCAD = M[1] * M[2] - M[0] * M[3];
+
+const convertRgbToCubehelix = ({ r, g, b, alpha }) => {
+	let l = (BCAD * b + r * DE - g * BE) / (BCAD + DE - BE);
+	let x = b - l;
+	let y = (M[4] * (g - l) - M[2] * x) / M[3];
+
+	let res = {
+		mode: 'cubehelix',
+		l: l,
+		s:
+			l === 0 || l === 1
+				? undefined
+				: Math.sqrt(x * x + y * y) / (M[4] * l * (1 - l))
+	};
+
+	if (res.s) res.h = Math.atan2(y, x) * radToDeg - 120;
+	if (alpha !== undefined) res.alpha = alpha;
+
+	return res;
+};
+
+export default convertRgbToCubehelix;