s = new Sprite();

var g:Graphics = s.graphics;

g.beginFill(0);

g.drawRect(0, 0, 100, 200);

g.endFill();

addChild(s);

var scale:Number = 0.2;

trace("centr pre scale:",s.x + (s.width >>1), s.y + (s.height>>1));

var p:Point = new Point(s.x + (s.width >> 1) - ((s.width * scale) >> 1), s.y + (s.height >> 1) -((s.height*scale) >> 1));

//trace(p);

Tweener.addTween(s, { scaleX:scale, scaleY:scale, x:p.x, y:p.y, delay: 2, time:0.5, onComplete: tweenCompleteHandler} );

 

function tweenCompleteHandler():void {

trace("centr after scale:",s.x + (s.width >>1), s.y + (s.height>>1));

}