1 files changed, 38 insertions, 0 deletions
diff --git a/node_modules/stylus/lib/functions/luminosity.js b/node_modules/stylus/lib/functions/luminosity.js
new file mode 100644
index 00000000..6b6cf7d0
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+++ b/node_modules/stylus/lib/functions/luminosity.js
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+var utils = require('../utils')
+  , nodes = require('../nodes');
+
+/**
+ * Returns the relative luminance of the given `color`,
+ * see http://www.w3.org/TR/WCAG20/#relativeluminancedef
+ *
+ * Examples:
+ *
+ *     luminosity(white)
+ *     // => 1
+ * 
+ *     luminosity(#000)
+ *     // => 0
+ * 
+ *     luminosity(red)
+ *     // => 0.2126
+ *
+ * @param {RGBA|HSLA} color
+ * @return {Unit}
+ * @api public
+ */
+
+module.exports = function luminosity(color){
+  utils.assertColor(color);
+  color = color.rgba;
+  function processChannel(channel) {
+    channel = channel / 255;
+    return (0.03928 > channel)
+      ? channel / 12.92
+      : Math.pow(((channel + 0.055) / 1.055), 2.4);
+  }
+  return new nodes.Unit(
+    0.2126 * processChannel(color.r)
+    + 0.7152 * processChannel(color.g)
+    + 0.0722 * processChannel(color.b)
+  );
+};