aaron-harvey · March 25, 2024 14:36 · May 26, 2011
diff --git a/scale.js b/scale.js
@@ -0,0 +1,19 @@
+/* Scale a value from one range to another
+* Example of use:
+*
+* // Convert 33 from a 0-100 range to a 0-65535 range
+* var n = scaleValue(33, [0,100], [0,65535]);
+*
+* // Ranges don't have to be positive
+* var n = scaleValue(0, [-50,+50], [0,65535]);
+*
+* Ranges are defined as arrays of two values, inclusive
+*
+* The ~~ trick on return value does the equivalent of Math.floor, just faster.
+*
+*/
+function scaleValue(value, from, to) {
+	var scale = (to[1] - to[0]) / (from[1] - from[0]);
+	var capped = Math.min(from[1], Math.max(from[0], value)) - from[0];
+	return ~~(capped * scale + to[0]);
+}