code: public static Point getPixelRelative(LatLong latLong, long mapSize, double x, double y) {
          double pixelX = MercatorProjection.longitudeToPixelX(latLong.longitude, mapSize) - x;
          double pixelY = MercatorProjection.latitudeToPixelY(latLong.latitude, mapSize) - y;
          return new Point(pixelX, pixelY);
      }
docs: Calculates the absolute pixel position for a map size and tile size relative to origin
  
  @param latLong the geographic position.
  @param mapSize precomputed size of map.
  @return the relative pixel position to the origin values (e.g. for a tile)