// Verschiebt die Matrix sodass aus der Mitte heraus skaliert wird
private function handleScale(event:GestureEvent):void {
    var targetElement:DisplayObject = event.target as DisplayObject;
    var registration:Point = new Point(targetElement.x + (targetElement.width / 2), targetElement.y + (targetElement.height / 2));

    var m:Matrix = targetElement.transform.matrix;
    m.translate(-registration.x, -registration.y);
    m.scale(event.scaleX, event.scaleY);
    m.translate(registration.x, registration.y);
    targetElement.transform.matrix = m;
}