百度瓦片地图制作

朴灿烈づ我的快乐病毒、 2022-06-09 02:12 367阅读 0赞

在网上查询了很久，找了很多百度瓦片地图下载文章，但是并没有我想要如何下载百度地图操作的文章教程。通过同事指点加自我摸索理解，总结如下关于下载百度瓦片地图制作的教程。

我们下载某个地区的地图，首先我们需要获取 **图块坐标**；

> 百度地图API在展示地图时是将整个地图图片切割成若干图块来显示的，当地图初始化或是地图级别、中心点位置发生变化时，地图API会根据当前像素坐标计算出视野内需要的图块坐标（也叫图块编号），从而加载对应的图块用以显示地图。  
> 百度地图的图块坐标原点与平面坐标一致，从原点向右上方开始编号为0, 0：  
> ![这里写图片描述][SouthEast]  
> 如何知道某个位置的图块坐标呢？通过如下公式计算即可（这里为向下取整）：  
> `图块坐标 =|像素坐标 ÷ 256|`  
> 256实际上是每个图块的宽度和高度，我们用像素坐标除以这个数就知道图块坐标了。还以天安门为例，在第4级下天安门所在的图块编号为：3, 1，而在第18级下，图块编号为：50617, 18851

**如何获取百度图块坐标?**  
打开百度开发平台：[http://lbsyun.baidu.com/jsdemo.htm?a\#i7\_1][http_lbsyun.baidu.com_jsdemo.htm_a_i7_1]  
将如下代码放入编辑器运行：

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8"/>
    <title>地图坐标概念</title>
    <script src="http://api.map.baidu.com/api?v=1.2"></script>
    </head>
    <body>
    <div id="map_container" style="width:500px;height:320px;"></div>
    <script> var map =new BMap.Map('map_container', {defaultCursor: 'default'}); map.centerAndZoom(new BMap.Point(116.404, 39.915), 11); var TILE_SIZE =256; map.addEventListener('click', function(e){ var info =new BMap.InfoWindow('', {width: 260}); var projection =this.getMapType().getProjection(); var lngLat = e.point; var lngLatStr ="经纬度："+ lngLat.lng +", "+ lngLat.lat; var worldCoordinate = projection.lngLatToPoint(lngLat); var worldCoordStr ="<br />平面坐标："+ worldCoordinate.x +", "+ worldCoordinate.y; var pixelCoordinate =new BMap.Pixel(Math.floor(worldCoordinate.x * Math.pow(2, this.getZoom() -18)), Math.floor(worldCoordinate.y * Math.pow(2, this.getZoom() -18))); var pixelCoordStr ="<br />像素坐标："+ pixelCoordinate.x +", "+ pixelCoordinate.y; var tileCoordinate =new BMap.Pixel(Math.floor(pixelCoordinate.x /256), Math.floor(pixelCoordinate.y /256)); var tileCoordStr ="<br />图块坐标："+ tileCoordinate.x +", "+ tileCoordinate.y; var viewportCoordinate = map.pointToPixel(lngLat); var viewportCoordStr ="<br />可视区域坐标："+ viewportCoordinate.x +", "+ viewportCoordinate.y; var overlayCoordinate = map.pointToOverlayPixel(lngLat); var overlayCoordStr ="<br />覆盖物坐标："+ overlayCoordinate.x +", "+ overlayCoordinate.y; info.setContent(lngLatStr + worldCoordStr + pixelCoordStr + tileCoordStr + viewportCoordStr + overlayCoordStr); map.openInfoWindow(info, lngLat); }); </script>
    </body>
    </html>

运行出来之后点击地图上会出现如图：  
![这里写图片描述][SouthEast 1]  
如此可以轻松地获取**图块坐标**信息。

**如何下载百度瓦片?**  
通过上述可以轻松获取到地域图块坐标范围值。  
提供如下**Java代码**下载瓦片图片：

import java.io.File;
    import java.io.FileOutputStream;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.List;
    import java.util.Map;
    import java.util.Set;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    import com.google.common.collect.Lists;
    import com.google.common.collect.Maps;
    import com.google.common.collect.Sets;
    
    /** * <pre> * 参考资料： * <a href="http://www.jianshu.com/p/0b292688b6af">国内主要地图瓦片坐标系定义及计算原理</a> * <a href="http://www.cnblogs.com/xiaozhi_5638/p/4748186.html">百度地图根据经纬度计算瓦片行列号</a> * */
    public class R implements Runnable { 
    
        static int succeed = 0;
        static int error = 0;
        static int finishedThread = 0;
        static long endTime = 0;
        static String sPath = "http://online1.map.bdimg.com/onlinelabel/?qt=tile&x=%d&y=%d&z=%d&styles=pl&udt=20150924&scaler=1";
        /** * z : 层级 * xstart : x的开始值 * xend : x的最大值 * ystart : y的开始值 * yend : y的最大值 * threads : 几个线程开始下载地图 */
        int z=11, xstart = 407,xend = 409,ystart = 113,yend = 116,threads = 1;
        //下载瓦片地图存放地址
        String dir = ""; 
        //是否覆盖之前下载的图片
        boolean overwrite = false; 
    
        Map<String, String> map = Maps.newHashMap();
        public R(Map<String, String> map) {
            this.map = map;
        }
    
        public static void main(String[] args) {
    
            final Map<String, String> map = Maps.newHashMap();
    
            /*Lists.newArrayList(args).forEach(s -> { String k = s.split("=")[0]; String v = s.split("=")[1]; map.put(k, v); });*/
            List<String> list = Lists.newArrayList(args);
            for(String str : list){
                String k = str.split("=")[0];
                String v = str.split("=")[1];
                map.put(k, v);
            }
            new R(map).run();
    
        }
    
        public void run() {
            ExecutorService exec = Executors.newCachedThreadPool();
    
            Set<Point> set = Sets.newHashSet();
    
            int total = (xend - xstart) * (yend - ystart);
    
            int split = total / threads;
            int count = 0;
            for(int i=xstart;i<=xend;i++) {
                for(int j=ystart;j<yend;j++) {
                    set.add(new Point(i, j));
                    if(++count % split == 0) {
                        exec.execute(new DownloadThread(set));
                        set = Sets.newHashSet();
                    }
                }
            }
            if(set.size()>0) {
                exec.execute(new DownloadThread(set));
            }
    
            long t = System.currentTimeMillis();
            while (finishedThread < threads) {
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                }
                System.out.println("耗时 " + (System.currentTimeMillis() - t) / 1000 + "s 成功 " + succeed + " 失败 " + error + " ok="+finishedThread+" total = "+total);
            }
            exec.shutdown();
            System.out.println("完成 共耗时 " + (endTime - t) / 1000 + "s 成功 " + succeed + " 失败 " + error + " ok="+finishedThread+" total = "+total);
        }
    
        class DownloadThread extends Thread {
            Set<Point> set;
            public DownloadThread(Set<Point> set) {
                this.set = set;
            }
    
            public void run() {
                System.out.println(getName() + " started, task size = " + set.size());
                File base = new File(dir, z + "");
    
                for(Point point : set) {
                    int x = point.x;
                    int y = point.y;
                    File path = new File(base, x + "");
                    if (!path.exists()) {
                        path.mkdirs();
                    }
                    File file = new File(path, y + ".jpg");
                    if (!file.exists() || overwrite) {
                        String url = String.format(sPath, x, y, z);
                        boolean b = save(url, file);
                        if (b) {
                            succeed++;
                            System.out.println(file.getAbsolutePath());
                        } else {
                            error++;
                        }
                    }
                }
                System.out.println(getName()+" finished");
                finishedThread++;
                endTime = System.currentTimeMillis();
            }
    
            byte[] b = new byte[4096];
            int s = 0;
    
            boolean save(String path, File file) {
                InputStream is = null;
                OutputStream os = null;
                try {
                    URL url = new URL(path);
                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                    conn.connect();
                    is = conn.getInputStream();
                    os = new FileOutputStream(file);
                    while ((s = is.read(b)) != -1) {
                        os.write(b, 0, s);
                    }
                    return true;
                } catch (Exception e) {
                    return false;
                } finally {
                    if (os != null) {
                        try {
                            os.flush();
                            os.close();
                        } catch (Exception e) {
                        }
                    }
                    if (is != null) {
                        try {
                            is.close();
                        } catch (Exception e) {
                        }
                    }
                }
            }
        }
    
        static class Point {
            int x, y;
            Point(int x,int y){
                this.x = x;
                this.y = y;
            }
        }
    }

通过上述java代码，修改其中参数值，百度瓦片地图下载到指定路径下。

[SouthEast]: /images/20220609/4a2438deed3b4cabac2e5a28ceec93f5.png
[http_lbsyun.baidu.com_jsdemo.htm_a_i7_1]: http://lbsyun.baidu.com/jsdemo.htm?a#i7_1
[SouthEast 1]: /images/20220609/88daa4fa2f214811b68cd3c29e916fbd.png