百度地图JavaScript离线开发：API加载、瓦片获取与坐标转换实战

var bdmapcfg = {
 'imgext':'.jpg', //瓦片图的后缀 ------ 根据需要修改，一般是 .png .jpg
 'tiles_dir':''  //瓦片图的目录，为空默认在 baidumap_v2/tiles/ 目录
};

  <script type="text/javascript"> 
  // 百度地图API功能
  var map = new BMap.Map("map_demo");  // 创建Map实例
  map.centerAndZoom(new BMap.Point(116.404, 39.915), 8); // 初始化地图,设置中心点坐标和地图级别
  //map.addControl(new BMap.MapTypeControl());  //添加地图类型控件 离线只支持电子地图，卫星/三维不支持
  //map.setCurrentCity("北京");     // 设置地图显示的城市 离线地图不支持！！
  map.enableScrollWheelZoom(true);   //开启鼠标滚轮缩放
  map.addControl(new BMap.NavigationControl());  //缩放按钮
  </script>

public class CoorConvertUtil {
    //圆周率
    static double pi = 3.14159265358979324;
    //卫星椭球坐标投影到平面坐标系的投影因子
    static double a = 6378245.0;
    //椭球的偏心率
    static double ee = 0.00669342162296594323;
    //圆周率转换量
    public final static double x_pi = 3.14159265358979324 * 3000.0 / 180.0;
    
    public static double[] wgs2bd(double lat, double lon){
      double[] wgs2gcj = wgs2gcj(lat, lon);
      double[] gcj2bd = gcj2bd(wgs2gcj[0], wgs2gcj[1]);
      return gcj2bd;
    }
    
    /**
     * GCJ坐标转百度坐标
     * @param lat
     * @param lon
     * @return
     */
    public static double[] gcj2bd(double lat, double lon) {
      double x = lon, y = lat;
      double z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
      double theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
      double bd_lon = z * Math.cos(theta) + 0.0065;
      double bd_lat = z * Math.sin(theta) + 0.006;
      return new double[] { bd_lat, bd_lon };
    }
    
    public static double[] bd2gcj(double lat, double lon) {
      double x = lon - 0.0065, y = lat - 0.006;
      double z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * x_pi);
      double theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * x_pi);
      double gg_lon = z * Math.cos(theta);
      double gg_lat = z * Math.sin(theta);
      return new double[] { gg_lat, gg_lon };
    }
    
    /**
     * WGS坐标转GCJ坐标
     * @param lat
     * @param lon
     * @return
     */
    public static double[] wgs2gcj(double lat, double lon) {
      double dLat = transformLat(lon - 105.0, lat - 35.0);
      double dLon = transformLon(lon - 105.0, lat - 35.0);
      double radLat = lat / 180.0 * pi;
      double magic = Math.sin(radLat);
      magic = 1 - ee * magic * magic;
      double sqrtMagic = Math.sqrt(magic);
      dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
      dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
      double mgLat = lat + dLat;
      double mgLon = lon + dLon;
      double[] loc = { mgLat, mgLon };
      return loc;
    }
    
    private static double transformLat(double lat, double lon) {
      double ret = -100.0 + 2.0 * lat + 3.0 * lon + 0.2 * lon * lon + 0.1 * lat * lon + 0.2 * Math.sqrt(Math.abs(lat));
      ret += (20.0 * Math.sin(6.0 * lat * pi) + 20.0 * Math.sin(2.0 * lat * pi)) * 2.0 / 3.0;
      ret += (20.0 * Math.sin(lon * pi) + 40.0 * Math.sin(lon / 3.0 * pi)) * 2.0 / 3.0;
      ret += (160.0 * Math.sin(lon / 12.0 * pi) + 320 * Math.sin(lon * pi/ 30.0)) * 2.0 / 3.0;
      return ret;
    }
    
    private static double transformLon(double lat, double lon) {
      double ret = 300.0 + lat + 2.0 * lon + 0.1 * lat * lat + 0.1 * lat * lon + 0.1 * Math.sqrt(Math.abs(lat));
      ret += (20.0 * Math.sin(6.0 * lat * pi) + 20.0 * Math.sin(2.0 * lat * pi)) * 2.0 / 3.0;
      ret += (20.0 * Math.sin(lat * pi) + 40.0 * Math.sin(lat / 3.0 * pi)) * 2.0 / 3.0;
      ret += (150.0 * Math.sin(lat / 12.0 * pi) + 300.0 * Math.sin(lat / 30.0 * pi)) * 2.0 / 3.0;
      return ret;
    }
    
    /**
     * 度分转度
     * @param lat 纬度 ddmm.mmmm
     * @param lon 经度 dddmm.mmmm
     * @return
     */
    public static double[] dufen2du(String lat, String lon){
      double latD=Double.parseDouble(lat.substring(0, 2));
      double latM=Double.parseDouble(lat.substring(2));
      double latNew=latD+latM/60;
      double lonD=Double.parseDouble(lon.substring(0, 3));
      double lonM=Double.parseDouble(lon.substring(3));
      double lonNew=lonD+lonM/60;
      return new double[] { latNew, lonNew } ;
    }
}