gistfile1.as

package
{
    import flash.display.Bitmap;
    import flash.display.Sprite;
    
    public class CenteredImage extends Sprite
    {
        private var _image:Bitmap;
        
        public function CenteredImage( image:Bitmap )
        {
            _image = image;
            _image.x = _image.y = 0;
            
            addChild( _image );
            addEventListener( Event.ADDED_TO_STAGE, onAddedToStage );
        }
        
        private function onAddedToStage( event:Event ):void
        {
            x = parent.width * 0.5 - width * 0.5;
            y = parent.height* 0.5 - height * 0.5;
        }
    }
}