[css-color-4] add porting hint regarding sign-preserving cube root

svgeesus · svgeesus · commit 6407b4e4c9f8 · 2023-10-26T18:23:54.000-04:00
diff --git a/css-color-4/conversions.js b/css-color-4/conversions.js
@@ -410,6 +410,9 @@ function XYZ_to_OKLab(XYZ) {
 	];
 
 	var LMS = multiplyMatrices(XYZtoLMS, XYZ);
+	// JavaScript Math.cbrt returns a sign-matched cube root
+	// beware if porting to other languages
+	// especially if tempted to use a general power function
 	return multiplyMatrices(LMStoOKLab, LMS.map(c => Math.cbrt(c)));
 	// L in range [0,1]. For use in CSS, multiply by 100 and add a percent
 }

Original file line number	Diff line number	Diff line change
`@@ -410,6 +410,9 @@ function XYZ_to_OKLab(XYZ) {`
`410`	`410`	`];`
`411`	`411`
`412`	`412`	`var LMS = multiplyMatrices(XYZtoLMS, XYZ);`
	`413`	`+ // JavaScript Math.cbrt returns a sign-matched cube root`
	`414`	`+ // beware if porting to other languages`
	`415`	`+ // especially if tempted to use a general power function`
`413`	`416`	`return multiplyMatrices(LMStoOKLab, LMS.map(c => Math.cbrt(c)));`
`414`	`417`	`// L in range [0,1]. For use in CSS, multiply by 100 and add a percent`
`415`	`418`	`}`