private function rotateClickHandler( evt:MouseEvent ):void {
			// bitmaps
			var oldBD:BitmapData = _currentBitmap.bitmapData;
			var newBD:BitmapData = new BitmapData(oldBD.height, oldBD.width, false, 0xFFFFFFFF);
			// matrix
			var matrix:Matrix = new Matrix();
			matrix.rotate( 90*(Math.PI/180) );
			matrix.translate( newBD.width, 0 );
			// draw
			newBD.draw(oldBD, matrix);
			// new bitmap
			var newBitmap:Bitmap = new Bitmap(newBD);
			// delete old
			oldBD.dispose();
			_bitmapContent.removeChild(_currentBitmap);
			// add new
			_currentBitmap = newBitmap;
			_bitmapContent.addChild(_currentBitmap);
		}