Android Open Source - android-open-street-map Projection

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License

The source code is released under:
Apache License
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Java Source Code

package com.android.lib.map.osm;
/* w  w  w.  j a va 2 s  .  c  om*/

public class Projection {

  // OrignShift  2 * math.pi * 6378137 / 2.0
  private final static double MAX_X = 20037508.342789244;
  private final static double MAX_Y = 20037508.342789244;
  
  public static double getMapSize(int zoomLevel) {
    double mapSize = (Math.pow(2, zoomLevel) * Tile.TILE_SIZE);
    return mapSize;
  }
  
  public static int getXPixelFromLongitude(double lon, int zoomLevel) {
    double mapWidth = getMapSize(zoomLevel);

    // Converts given lon in WGS84 Datum to XY in Spherical Mercator EPSG:900913
    double x = lon * MAX_X / 180.0;
    
    // Scale to map
    x = ((x + MAX_X) / (MAX_X * 2)) * mapWidth;
    
    return (int) x;
  }

  public static int getYPixelFromLatitude(double lat, int zoomLevel) {
    double mapWidth = getMapSize(zoomLevel);    
    
    //Converts given lat in WGS84 Datum to XY in Spherical Mercator EPSG:900913
      double y= Math.log( Math.tan((90 + lat) * Math.PI / 360.0 )) / (Math.PI / 180.0);
      y = y * MAX_Y / 180.0;
      
      // Scale to map
      y = mapWidth - (((y + MAX_Y) / (MAX_Y * 2)) * mapWidth);
      
      return (int) y;
  }
  
  public static GeoPoint getProjectionFromPixels(int x, int y, int zoom) {
    //Converts XY point from Spherical Mercator EPSG:900913 to lat/lon in WGS84 Datum
    
    double mapWidth = getMapSize(zoom);
    // Convert Map pixel to mercator coord
      double mercatorX = MAX_X - ((MAX_X * 2) * (x / mapWidth));
      double mercatorY = - (MAX_Y - ((MAX_Y * 2) * ((y + mapWidth) / mapWidth)));
    
    double lon = (mercatorX / MAX_X) * 180.0;
        double lat = (mercatorY / MAX_Y) * 180.0;

        lat = 180 / Math.PI * (2 * Math.atan( Math.exp( lat * Math.PI / 180.0)) - Math.PI / 2.0);
    
    return new GeoPoint((int) (lat * 1E6) , (int) (lon * 1E6));
  }

  public static int getZoomLevelFromBox(double maxLat, double maxLon, double minLat,
      double minLon, int viewWidth, int viewHeight) {
    
    return getZoomLevelFromBox(maxLat, maxLon, minLat, minLon, viewWidth, viewHeight, 0, 0);
  }
  
  public static int getZoomLevelFromBox(double maxLat, double maxLon, double minLat,
      double minLon, int viewWidth, int viewHeight, int viewPaddingWidth, int viewPaddingHeight) {

    // Reduce view by XX pixels to not have markers or tracks on edge of screen 
    viewWidth -= viewPaddingWidth;
    viewHeight -= viewPaddingHeight;
    //---
    
    int zoomLevel;
    int maxLatOffset;
    int minLonOffset;
    int maxLatE6 = (int) (maxLat * 1E6);
    int maxLonE6 = (int) (maxLon * 1E6);
    int minLatE6 = (int) (minLat * 1E6);
    int minLonE6 = (int) (minLon * 1E6);
    
  //  Log.i("getZoomLevelFromBox", "maxLatE6:" + maxLatE6 + "  maxLonE6:" + maxLonE6 + "  minLatE6:" + minLatE6 + "  minLonE6:" + minLonE6);
    
    for (zoomLevel = OsmMapViewBase.MIN_ZOOM_LEVEL_FOR_TILES; zoomLevel > 0; zoomLevel--) {
      
      maxLatOffset = (0 - Projection.getYPixelFromLatitude(maxLat, zoomLevel));
      minLonOffset = (0 - Projection.getXPixelFromLongitude(minLon, zoomLevel));
      
      GeoPoint upperLeftScreen = Projection.getProjectionFromPixels(minLonOffset, maxLatOffset, zoomLevel);
      GeoPoint lowerRightcreen = Projection.getProjectionFromPixels(
          minLonOffset - viewWidth, 
          maxLatOffset - viewHeight, 
          zoomLevel);
    
    //  Log.i("getZoomLevelFromBox", "upperLeftScreen.getLatitudeE6():" + upperLeftScreen.getLatitudeE6() + "   upperLeftScreen.getLongitudeE6():" + upperLeftScreen.getLongitudeE6() 
    //      + "   lowerRightcreen.getLatitudeE6():" + lowerRightcreen.getLatitudeE6() + "   lowerRightcreen.getLongitudeE6():" + lowerRightcreen.getLongitudeE6());
      
      if (upperLeftScreen.getLatitudeE6() >= maxLatE6
          && upperLeftScreen.getLongitudeE6() <= minLonE6
          && lowerRightcreen.getLatitudeE6() <= minLatE6
          && lowerRightcreen.getLongitudeE6() >= maxLonE6) {
        
        //fit in screen
        break;
      }
    }
    
    return zoomLevel;
  }
  
  public static Tile getMapTileFromCoordinates(final double lat, final double lon, final int zoom) {
    final int y = (int) Math.floor((1 - Math.log(Math.tan(lat * Math.PI / 180) + 1 / Math.cos(lat * Math.PI / 180)) / Math.PI) / 2 * (1 << zoom));
    final int x = (int) Math.floor((lon + 180) / 360 * (1 << zoom));

    Tile tile = new Tile(x, y, zoom);
    return tile;
  }
}
Java Source Code List
