private static boolean a4 (int i, int j, BufferedImage image) {
      boolean ul    = ((image.getRGB(i-1, j  ) == BLACK) ||
                       (image.getRGB(i-1, j+1) == BLACK) ||
                       (image.getRGB(i  , j+1) == BLACK));
      
      boolean with  = ((image.getRGB(i-1, j-1) == WHITE) && 
                       (image.getRGB(i  , j  ) == BLACK) &&
                       (image.getRGB(i+1, j+1) == WHITE));
      
      boolean lr    = ((image.getRGB(i+1, j  ) == BLACK) ||
                       (image.getRGB(i+1, j-1) == BLACK) ||
                       (image.getRGB(i  , j-1) == BLACK));
      
      return ( ul && with && lr );
   }