return null; }
double centrex, centrey; Dimension tileSize = getTileSize(zoom); Polygon poly = new Polygon();  centrex = tx*tileSize.getWidth() + tileSize.getWidth() / 2; centrey = ty*tileSize.getHeight() + tileSize.getHeight() / 2;   poly.addPoint((int) (centrex - tileSize.getWidth()/2), (int) centrey); poly.addPoint((int) (centrex - tileSize.getWidth() / 4), (int) (centrey - tileSize.getHeight() / 2)); poly.addPoint((int) (centrex + tileSize.getWidth() / 4), (int) (centrey - tileSize.getHeight() / 2)); poly.addPoint((int) (centrex + tileSize.getWidth() / 2), (int) centrey); poly.addPoint((int) (centrex + tileSize.getWidth() / 4), (int) (centrey + tileSize.getHeight() / 2)); poly.addPoint((int) (centrex - tileSize.getWidth() / 4), (int) (centrey + tileSize.getHeight() / 2));  return poly; }
	protected Polygon createGridPolygon(int tx, int ty, int border) {		// TODO Auto-generated method stub		return null;	}