代码设置显示对象的注册点

public static function setRegPoint(obj:DisplayObjectContainer, newX:Number, newY:Number):void {
			//get the bounds of the object and the location
			//of the current registration point in relation
			//to the upper left corner of the graphical content
			//note: this is a PSEUDO currentRegX and currentRegY, as the
			//registration point of a display object is ALWAYS (0, 0):
			var bounds:Rectangle = obj.getBounds(obj.parent);
			var currentRegX:Number = obj.x - bounds.left;
			var currentRegY:Number = obj.y - bounds.top;
			
			var xOffset:Number = newX - currentRegX;
			var yOffset:Number = newY - currentRegY;
			//shift the object to its new location--
			//this will put it back in the same position
			//where it started (that is, VISUALLY anyway):
			obj.x += xOffset;
			obj.y += yOffset;
			
			//shift all the children the same amount,
			//but in the opposite direction
			for(var i:int = 0; i < obj.numChildren; i++) {
				obj.getChildAt(i).x -= xOffset;
				obj.getChildAt(i).y -= yOffset;
			}
		}

这样缩放的时候，就会根据注册点来缩放了