Ocultar Imagem com Flex

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" width="486" height="330">
	<mx:Script>
		<![CDATA[
			private function ocultar():void {
				img.visible = false;
			}
		]]>
	</mx:Script>

	<mx:Panel x="68" y="30" width="350" height="250" layout="absolute" title="Ocultar Imagem">
		<mx:Image source="@Embed('imagens/desert.jpg')" id="img" width="100%" height="100%"/>
		<mx:Button x="283" y="94" label="OK" click="ocultar();"/>
	</mx:Panel>

</mx:Application>