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

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

@@ -0,0 +1,28 @@
+var utils = require('../utils');
+
+/**
+ * Adjust HSL `color` `prop` by `amount`.
+ *
+ * @param {RGBA|HSLA} color
+ * @param {String} prop
+ * @param {Unit} amount
+ * @return {RGBA}
+ * @api private
+ */
+
+module.exports = function adjust(color, prop, amount){
+  utils.assertColor(color, 'color');
+  utils.assertString(prop, 'prop');
+  utils.assertType(amount, 'unit', 'amount');
+  var hsl = color.hsla.clone();
+  prop = { hue: 'h', saturation: 's', lightness: 'l' }[prop.string];
+  if (!prop) throw new Error('invalid adjustment property');
+  var val = amount.val;
+  if ('%' == amount.type){
+    val = 'l' == prop && val > 0
+      ? (100 - hsl[prop]) * val / 100
+      : hsl[prop] * (val / 100);
+  }
+  hsl[prop] += val;
+  return hsl.rgba;
+};