added data url support for Kinetic.Image, and added unit tests

dist/kinetic-core.js

@@ -80,15 +80,18 @@ Kinetic.Type = {
     _isFunction: function(obj) {
         return !!(obj && obj.constructor && obj.call && obj.apply);
     },
-    _isArray: function(obj) {
-        return Object.prototype.toString.call(obj) == '[object Array]';
-    },
     _isObject: function(obj) {
         return (!!obj && obj.constructor == Object);
     },
+    _isArray: function(obj) {
+        return Object.prototype.toString.call(obj) == '[object Array]';
+    },
     _isNumber: function(obj) {
         return Object.prototype.toString.call(obj) == '[object Number]';
     },
+    _isString: function(obj) {
+        return Object.prototype.toString.call(obj) == '[object String]';
+    },
     /*
      * other utils
      */
@@ -280,7 +283,14 @@ Kinetic.Type = {
             return arg;
         }
 
-        //if arg is image data, then convert it
+        // if arg is a string, then it's a data url
+        if(this._isString(arg)) {
+            var imageObj = new Image();
+            imageObj.src = arg;
+            return imageObj;
+        }
+
+        //if arg is an object that contains the data property, it's an image object
         if(arg.data) {
             var canvas = document.createElement('canvas');
             canvas.width = arg.width;