code: public static double[] tileLatLonBounds( int tx, int ty, int zoom, int tileSize ) {
          double[] bounds = tileBounds3857(tx, ty, zoom, tileSize);
          double[] mins = metersToLatLon(bounds[0], bounds[1]);
          double[] maxs = metersToLatLon(bounds[2], bounds[3]);
          return new double[]{mins[1], maxs[0], maxs[1], mins[0]};
      }
docs: Get lat-long bounds from tile index.
  
  @param tx       tile x.
  @param ty       tile y.
  @param zoom     zoomlevel.
  @param tileSize tile size.
  @return [minx, miny, maxx, maxy]