complete redesign: use nodejs on server instead of php - documentation to be updated

nodejs/node_modules/stylus/lib/functions/blend.js

@@ -0,0 +1,37 @@
+var utils = require('../utils')
+  , nodes = require('../nodes');
+
+/**
+ * Blend the `top` color over the `bottom`
+ *
+ * Examples:
+ *
+ *     blend(rgba(#FFF, 0.5), #000)
+ *     // => #808080
+ * 
+ *     blend(rgba(#FFDE00,.42), #19C261)
+ *     // => #7ace38
+ * 
+ *     blend(rgba(lime, 0.5), rgba(red, 0.25))
+ *     // => rgba(128,128,0,0.625)
+ *
+ * @param {RGBA|HSLA} top
+ * @param {RGBA|HSLA} [bottom=#fff]
+ * @return {RGBA}
+ * @api public
+ */
+
+module.exports = function blend(top, bottom){
+  // TODO: different blend modes like overlay etc.
+  utils.assertColor(top);
+  top = top.rgba;
+  bottom = bottom || new nodes.RGBA(255, 255, 255, 1);
+  utils.assertColor(bottom);
+  bottom = bottom.rgba;
+
+  return new nodes.RGBA(
+    top.r * top.a + bottom.r * (1 - top.a),
+    top.g * top.a + bottom.g * (1 - top.a),
+    top.b * top.a + bottom.b * (1 - top.a),
+    top.a + bottom.a - top.a * bottom.a);
+};