Merge pull request #1890 from roelvanduijnhoven/feature/luma-definition

Let `luma` follow spec

Author: lukeapage

lib/less/functions.js

@@ -95,6 +95,14 @@ tree.functions = {
     luma: function (color) {
         return new(tree.Dimension)(Math.round(color.luma() * color.alpha * 100), '%');
     },
+    luminance: function (color) {
+        var luminance =
+            (0.2126 * color.rgb[0] / 255)
+          + (0.7152 * color.rgb[1] / 255)
+          + (0.0722 * color.rgb[2] / 255);
+
+        return new(tree.Dimension)(Math.round(luminance * color.alpha * 100), '%');
+    },
     saturate: function (color, amount) {
         // filter: saturate(3.2);
         // should be kept as is, so check for color

lib/less/tree/color.js

@@ -28,7 +28,17 @@ var transparentKeyword = "transparent";
 tree.Color.prototype = {
     type: "Color",
     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); },
+    luma: function () {
+        var r = this.rgb[0] / 255,
+            g = this.rgb[1] / 255,
+            b = this.rgb[2] / 255;
+
+        r = (r <= 0.03928) ? r / 12.92 : Math.pow(((r + 0.055) / 1.055), 2.4);
+        g = (g <= 0.03928) ? g / 12.92 : Math.pow(((g + 0.055) / 1.055), 2.4);
+        b = (b <= 0.03928) ? b / 12.92 : Math.pow(((b + 0.055) / 1.055), 2.4);
+
+        return 0.2126 * r + 0.7152 * g + 0.0722 * b;
+    },
 
     genCSS: function (env, output) {
         output.add(this.toCSS(env));

test/css/functions.css

@@ -24,7 +24,12 @@
   luma-blue: 7%;
   luma-yellow: 93%;
   luma-cyan: 79%;
-  luma-white-alpha: 50%;
+  luma-differs-from-luminance: 24%;
+  luminance-white: 100%;
+  luminance-black: 0%;
+  luminance-black-alpha: 0%;
+  luminance-red: 21%;
+  luminance-differs-from-luma: 36%;
   contrast-filter: contrast(30%);
   saturate-filter: saturate(5%);
   contrast-white: #000000;

test/less/functions.less

@@ -28,7 +28,12 @@
   luma-blue: luma(#0000ff);
   luma-yellow: luma(#ffff00);
   luma-cyan: luma(#00ffff);
-  luma-white-alpha: luma(rgba(255,255,255,0.5));
+  luma-differs-from-luminance: luma(#ff3600);
+  luminance-white: luma(#fff);
+  luminance-black: luma(#000);
+  luminance-black-alpha: luma(rgba(0,0,0,0.5));
+  luminance-red: luma(#ff0000);
+  luminance-differs-from-luma: luminance(#ff3600);
   contrast-filter: contrast(30%);
   saturate-filter: saturate(5%);
   contrast-white: contrast(#fff);
@@ -44,11 +49,11 @@
   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);
-  contrast-low-thresh: contrast(#555, #111111, #eeeeee, 0.1);
+  contrast-low-thresh: contrast(#555, #111111, #eeeeee, 0.09);
   contrast-light-thresh-per: contrast(#fff, #111111, #eeeeee, 50%);
   contrast-dark-thresh-per: contrast(#000, #111111, #eeeeee, 50%);
   contrast-high-thresh-per: contrast(#555, #111111, #eeeeee, 60%);
-  contrast-low-thresh-per: contrast(#555, #111111, #eeeeee, 10%);
+  contrast-low-thresh-per: contrast(#555, #111111, #eeeeee, 9%);
   replace: replace("Hello, Mars.", "Mars\.", "World!");
   replace-captured: replace("This is a string.", "(string)\.$", "new $1.");
   replace-with-flags: replace("One + one = 4", "one", "2", "gi");