JAVA代碼根據經緯度範圍計算WGS84與Google全球墨卡托包含的切片數目與拼接映像像素尺寸

標籤：範圍   切圖   log   system   mat   項目   double   return   Google地圖   

根據項目需求編寫的代碼。

適用情境：在網路地圖上，比如天地圖與Google地圖，使用者用滑鼠在地圖上拉一個矩形框，希望下載該矩形框內某一層級的瓦片資料，並將所有瓦片拼接成一個完整的，包含地理座標的tif映像。

那麼在下載瓦片與拼接瓦片之前，使用者希望能看到待下載的瓦片數量與待拼接映像的像素尺寸，再決定是否拼接。

該java代碼根據該矩形框的經緯度範圍與使用者指定的瓦片層級，計算需要下載的瓦片數量與待拼接結果映像的像素尺寸。

支援EPSG4326經緯度與EPSG3857Google全球墨卡托投影。經緯度瓦片切圖規則與天地圖相同，從第一層開始切，第一層包含兩個瓦片。Google全球墨卡托從第0層開始切，第0層一個瓦片。

public class Main {

    private void LonLatToTile(double lon,double lat,int zoom,int[] txy)
    {
        double resFact = 180.0 / 256.0;
        double[] pxy = new double[]{0.0,0.0};
        double res = resFact / Math.pow(2,(double)zoom);
        pxy[0] = (180.0 + lon) / res;
        pxy[1] = (90.0 - lat) / res;

        txy[0] = (int)(Math.ceil(pxy[0]/256.0) - 1);
        txy[1] = (int)(Math.ceil(pxy[1]/256.0) - 1);
    }

    private void LatLonToMeters(double lon, double lat,double[] mxy)
    {
        double m_originShift = 2 * 3.141592653589793 * 6378137 / 2.0;

        mxy[0] = lon * m_originShift / 180.0;
        mxy[1] = Math.log( Math.tan((90 + lat) * 3.141592653589793 / 360.0 )) / (3.141592653589793 / 180.0);

        mxy[1] = mxy[1] * m_originShift / 180.0;
    }

    private void MetersToTile(double mx, double my, int zoom, int[] txy)
    {
        double m_initialResolution = 2 * 3.141592653589793 * 6378137 / 256;
        double m_originShift = 2 * 3.141592653589793 * 6378137 / 2.0;

        double res = m_initialResolution / Math.pow(2,(double)zoom);
        double px = (mx + m_originShift) / res;
        double py = (m_originShift - my) / res;

        txy[0] = (int)( Math.ceil( px / (float)(256) ) - 1 );
        txy[1] = (int)( Math.ceil( py / (float)(256) ) - 1 );
    }

    //  計算經緯度輸出瓦片數量與待拼接映像像素尺寸
    public int getGeodeticSize(double minLon, double maxLon, double minLat, double maxLat, int zoom, int[]  pixSize){

        int[] tminxy = new int[]{0,0};
        int[] tmaxxy = new int[]{0,0};

        LonLatToTile(minLon,minLat,zoom-1,tminxy);
        LonLatToTile(maxLon,maxLat,zoom-1,tmaxxy);

        pixSize[0] = (1+Math.abs(tmaxxy[0]-tminxy[0])) * 256;
        pixSize[1] = (1+Math.abs(tmaxxy[1]-tminxy[1])) * 256;

        int tnum = (1+Math.abs(tmaxxy[0]-tminxy[0])) * (1+Math.abs(tmaxxy[1]-tminxy[1]));

        return tnum;
    }
    //  計算Google投影輸出瓦片數量與待拼接映像像素尺寸
    public int getMercatorSize(double minLon, double maxLon, double minLat, double maxLat, int zoom, int[]  pixSize){

        double[] oULxy = new double[]{0,0};
        double[] oDRxy = new double[]{0,0};
        LatLonToMeters(minLon,maxLat,oULxy);
        LatLonToMeters(maxLon,minLat,oDRxy);
        double ominx = oULxy[0];
        double omaxx = oDRxy[0];
        double ominy = oDRxy[1];
        double omaxy = oULxy[1];

        int[] tminxy= new int[]{0,0};
        int[] tmaxxy = new int[]{0,0};
        MetersToTile(ominx,ominy, zoom, tminxy);
        MetersToTile(omaxx,omaxy, zoom, tmaxxy);

        pixSize[0] = (1+Math.abs(tmaxxy[0]-tminxy[0])) * 256;
        pixSize[1] = (1+Math.abs(tmaxxy[1]-tminxy[1])) * 256;

        int tnum = (1+Math.abs(tmaxxy[0]-tminxy[0])) * (1+Math.abs(tmaxxy[1]-tminxy[1]));

        return tnum;
    }

    public static void main(String[] args) {
        System.out.println("Hello World!");
        double minLon = 119.54384371341310;
        double maxLon = 119.93413672204591;
        double minLat = 33.068895415323247;
        double maxLat = 33.433168890047206;
        int zoom = 13;

        Main e=new Main();

        int[] pixSize= new int[]{0,0};
        int tnum;
        tnum = e.getGeodeticSize(minLon, maxLon, minLat, maxLat, zoom, pixSize);
        System.out.println("經緯度資料瓦片數：" + tnum + "      映像尺寸：" + pixSize[0] + "*" + pixSize[1]);
        tnum = e.getMercatorSize(minLon, maxLon, minLat, maxLat, zoom, pixSize);
        System.out.println("Google資料瓦片數：" + tnum + "        映像尺寸：" + pixSize[0] + "*" + pixSize[1]);

    }


}
運行結果：

JAVA代碼根據經緯度範圍計算WGS84與Google全球墨卡托包含的切片數目與拼接映像像素尺寸