[konst06]

Я делал так:

 private function resize(loader:Loader, needW:int, needH:int) {
 				var h:int = loader.content.height;
				var w:int = loader.content.width;
				var needW = 240;								
				var needH = 240;
				if (w > needW || h > needH) {
					var prop1:int = (needW*100) / w;
					var prop2:int = (needH*100) / h;					
					var prop:int = prop1 < prop2 ? prop1 : prop2;
					loader.content.width = (w * prop) / 100;					
					loader.content.height = (h * prop) / 100;					
				}
 
		 }