浏览器不显示图片，错误代码在这

错误代码：        imagettftext($this->image,$size,$angle,$local['x'],$local['y'],$col,$font_url,$content);

错误信息：Notice: Undefined index: x in C:\wamp\www\image\image.class.php on line 40

Notice: Undefined index: y in C:\wamp\www\image\image.class.php on line 40

Warning: imagettftext() expects parameter 3 to be double, array given in C:\wamp\www\image\image.class.php on line 40

上面的代码就是40行