code: public static int getFineDirection (int ax, int ay, int bx, int by)
      {
          return getFineDirection(Math.atan2(by-ay, bx-ax));
      }
docs: Returns which of the sixteen compass directions that point <code>b</code> lies in from
  point <code>a</code> as one of the {@link DirectionCodes} direction constants.
  <em>Note:</em> that the coordinates supplied are assumed to be logical (screen) rather than
  cartesian coordinates and <code>NORTH</code> is considered to point toward the top of the
  screen.