Better implementation of luma

lib/less/functions.js

@@ -84,10 +84,7 @@ tree.functions = {
         return new(tree.Dimension)(color.toHSL().a);
     },
     luma: function (color) {
-        return new(tree.Dimension)(Math.round((0.2126 * (color.rgb[0]/255) +
-            0.7152 * (color.rgb[1]/255) +
-            0.0722 * (color.rgb[2]/255)) *
-            color.alpha * 100), '%');
+        return new(tree.Dimension)(Math.round(color.luma() * color.alpha * 100), '%');
     },
     saturate: function (color, amount) {
         var hsl = color.toHSL();
@@ -184,12 +181,18 @@ tree.functions = {
         if (typeof dark === 'undefined') {
             dark = this.rgba(0, 0, 0, 1.0);
         }
+        //Figure out which is actually light and dark!
+        if (dark.luma() > light.luma()) {
+            var t = light;
+            light = dark;
+            dark = t;
+        }
         if (typeof threshold === 'undefined') {
             threshold = 0.43;
         } else {
             threshold = number(threshold);
         }
-        if (((0.2126 * (color.rgb[0]/255) + 0.7152 * (color.rgb[1]/255) + 0.0722 * (color.rgb[2]/255)) * color.alpha) < threshold) {
+        if ((color.luma() * color.alpha) < threshold) {
             return light;
         } else {
             return dark;

lib/less/tree/color.js

@@ -24,6 +24,7 @@ tree.Color = function (rgb, a) {
 };
 tree.Color.prototype = {
     eval: function () { return this },
+    luma: function () { return (0.2126 * this.rgb[0] / 255) + (0.7152 * this.rgb[1] / 255) + (0.0722 * this.rgb[2] / 255); },
 
     //
     // If we have some transparency, the only way to represent it

test/css/functions.css

@@ -34,6 +34,7 @@
   contrast-cyan: #000000;
   contrast-light: #111111;
   contrast-dark: #eeeeee;
+  contrast-wrongorder: #111111;
   contrast-light-thresh: #111111;
   contrast-dark-thresh: #eeeeee;
   contrast-high-thresh: #eeeeee;

test/less/functions.less

@@ -38,6 +38,7 @@
   contrast-cyan: contrast(#00ffff);
   contrast-light: contrast(#fff, #111111, #eeeeee);
   contrast-dark: contrast(#000, #111111, #eeeeee);
+  contrast-wrongorder: contrast(#fff, #eeeeee, #111111, 0.5);
   contrast-light-thresh: contrast(#fff, #111111, #eeeeee, 0.5);
   contrast-dark-thresh: contrast(#000, #111111, #eeeeee, 0.5);
   contrast-high-thresh: contrast(#555, #111111, #eeeeee, 0.6);