续上篇《Web版百度地图加载离线瓦片》，本文贴出下载瓦片的简易程序。
百度地图瓦片的下载其实很容易，拿到下载链接然后批量下载就行了。不过由于需要按照规则来存储，最好自己写个程序去下载这些链接。否则就要使用人家已经做好的程序去下载了，这些很多都是需要收费的，或者有水印什么的。
其实直接拿到地图窗口内的所有瓦片并非难事，跟踪一下脚本中的代码就行了。不过脚本是压缩混淆过的，读起来比较难。
本文直接贴出来整理好的代码，然后就可以调用下载了。
function downloadBaiduTiles(){
var EARTHRADIUS = 6370996.81;
var MCBAND = [ 12890594.86, 8362377.87, 5591021, 3481989.83,
1678043.12, 0 ];
var LLBAND = [ 75, 60, 45, 30, 15, 0 ];
var MC2LL = [
[ 1.410526172116255e-8, 0.00000898305509648872,
-1.9939833816331, 200.9824383106796,
-187.2403703815547, 91.6087516669843,
-23.38765649603339, 2.57121317296198,
-0.03801003308653, 17337981.2 ],
[ -7.435856389565537e-9, 0.000008983055097726239,
-0.78625201886289, 96.32687599759846,
-1.85204757529826, -59.36935905485877,
47.40033549296737, -16.50741931063887,
2.28786674699375, 10260144.86 ],
[ -3.030883460898826e-8, 0.00000898305509983578,
0.30071316287616, 59.74293618442277,
7.357984074871, -25.38371002664745,
13.45380521110908, -3.29883767235584,
0.32710905363475, 6856817.37 ],
[ -1.981981304930552e-8, 0.000008983055099779535,
0.03278182852591, 40.31678527705744,
0.65659298677277, -4.44255534477492,
0.85341911805263, 0.12923347998204,
-0.04625736007561, 4482777.06 ],
[ 3.09191371068437e-9, 0.000008983055096812155,
0.00006995724062, 23.10934304144901,
-0.00023663490511, -0.6321817810242,
-0.00663494467273, 0.03430082397953,
-0.00466043876332, 2555164.4 ],
[ 2.890871144776878e-9, 0.000008983055095805407,
-3.068298e-8, 7.47137025468032,
-0.00000353937994, -0.02145144861037,
-0.00001234426596, 0.00010322952773,
-0.00000323890364, 826088.5 ] ];
var LL2MC = [
[ -0.0015702102444, 111320.7020616939,
1704480524535203, -10338987376042340,
26112667856603880, -35149669176653700,
26595700718403920, -10725012454188240,
1800819912950474, 82.5 ],
[ 0.0008277824516172526, 111320.7020463578,
647795574.6671607, -4082003173.641316,
10774905663.51142, -15171875531.51559,
12053065338.62167, -5124939663.577472,
913311935.9512032, 67.5 ],
[ 0.00337398766765, 111320.7020202162,
4481351.045890365, -23393751.19931662,
79682215.47186455, -115964993.2797253,
97236711.15602145, -43661946.33752821,
8477230.501135234, 52.5 ],
[ 0.00220636496208, 111320.7020209128,
51751.86112841131, 3796837.749470245,
992013.7397791013, -1221952.21711287,
1340652.697009075, -620943.6990984312,
144416.9293806241, 37.5 ],
[ -0.0003441963504368392, 111320.7020576856,
278.2353980772752, 2485758.690035394,
6070.750963243378, 54821.18345352118,
9540.606633304236, -2710.55326746645,
1405.483844121726, 22.5 ],
[ -0.0003218135878613132, 111320.7020701615,
0.00369383431289, 823725.6402795718,
0.46104986909093, 2351.343141331292,
1.58060784298199, 8.77738589078284,
0.37238884252424, 7.45 ] ];
function Point(lng, lat){
this.lng = lng;
this.lat = lat;
}
function convertor (point, ll2mc) {
if (!point || !ll2mc) {
return
}
// 经度的转换比较简单，一个简单的线性转换就可以了。
// 0、1的数量级别是这样的-0.0015702102444, 111320.7020616939
var x = ll2mc[0] + ll2mc[1] * Math.abs(point.lng);
// 先计算一个线性关系，其中9的数量级是这样的：67.5，a的估值大约是一个个位数
var a = Math.abs(point.lat) / ll2mc[9];
// 维度的转换相对比较复杂，y=b+ca+da^2+ea^3+fa^4+ga^5+ha^6
// 其中，a是维度的线性转换，而最终值则是一个六次方的多项式，2、3、4、5、6、7、8的数值大约是这样的：
// 278.2353980772752, 2485758.690035394,
// 6070.750963243378, 54821.18345352118,
// 9540.606633304236, -2710.55326746645,
// 1405.483844121726,
// 这意味着维度会变成一个很大的数，大到多少很难说
var y = ll2mc[2] + ll2mc[3] * a + ll2mc[4] * a * a + ll2mc[5] * a
* a * a + ll2mc[6] * a * a * a * a + ll2mc[7] * a
* a * a * a * a + ll2mc[8] * a * a * a * a
* a * a;
// 整个计算是基于绝对值的，符号位最后补回去就行了
x *= (point.lng < 0 ? -1 : 1);
y *= (point.lat < 0 ? -1 : 1);
// 产生一个新的点坐标。果然不一样了啊
return new Point(x, y)
}
function lngLatToMercator(T) {
return convertLL2MC(T);
}
function getLoop(value, min, max) {
while (value > max) {
value -= max - min
}
while (value < min) {
value += max - min
}
return value
}
function convertLL2MC (point) {
var point1;
var ll2mc;
point.lng = getLoop(point.lng, -180, 180);// 标准化到区间内
point.lat = getRange(point.lat, -74, 74);// 标准化到区间内
point1 = new Point(point.lng, point.lat);
// 查找LLBAND的维度字典，字典由大到小排序，找到则停止
for (var i = 0; i < LLBAND.length; i++) {
if (point1.lat >= LLBAND[i]) {
ll2mc = LL2MC[i];
break;
}
}
// 如果没有找到，则反过来找。找到即停止。
if (!ll2mc) {
for (var i = LLBAND.length - 1; i >= 0; i--) {
if (point1.lat <= -LLBAND[i]) {
ll2mc = LL2MC[i];
break;
}
}
}
var newPoint = convertor(point, ll2mc);
var point = new Point(newPoint.lng.toFixed(2), newPoint.lat.toFixed(2));
return point;
}
function findAllTiles(map, callback){
var mapType = map.getMapType();// 地图类型
var zoomLevel = map.zoomLevel;// 放大倍数
var center = map.mercatorCenter;// 中心坐标
this.mapCenterPoint = center;
var cV = mapType.getZoomUnits(zoomLevel);// zoomLevel相关的一个指数，=2^(18-zoomLevel)
var unitSize = mapType.getZoomFactor(zoomLevel);// 一个系数，=cV*256
var longitudeUnits = Math.ceil(center.lng / unitSize);// center.lng是一个很大的数
var latitudeUnits = Math.ceil(center.lat / unitSize);
var tileSize = mapType.getTileSize();
var cP = [ longitudeUnits, latitudeUnits, (center.lng - longitudeUnits * unitSize) / unitSize * tileSize,
(center.lat - latitudeUnits * unitSize) / unitSize * tileSize ];
var width0 = cP[0] - Math.ceil((map.width / 2 - cP[2]) / tileSize);
var height0 = cP[1] - Math.ceil((map.height / 2 - cP[3]) / tileSize);
var width = cP[0] + Math.ceil((map.width / 2 + cP[2]) / tileSize);
var c0 = 0;
if (mapType === BMAP_PERSPECTIVE_MAP && map.getZoom() == 15) {
c0 = 1
}
var height = cP[1] + Math.ceil((map.height / 2 + cP[3]) / tileSize) + c0;
var xydata = [];
for (var i = width0; i < width; i++) {
for (var j = height0; j < height; j++) {
xydata.push([ i, j ])
}
}
var zoom = map.getZoom();
//var win = window.open();
for (var i = 0, len = xydata.length; i < len; i++) {
showTile([ xydata[i][0], xydata[i][1], zoom ], callback)
}
}
function showTile(xyz, callback){
console.log(xyz[2]+"/"+xyz[0]+"/"+xyz[1]);
if(!!callback){
callback(xyz, getTilesUrl({x:xyz[0],y:xyz[1]}, xyz[2]));
}
}
var j = [ "http://online0.map.bdimg.com/tile/",
"http://online1.map.bdimg.com/tile/",
"http://online2.map.bdimg.com/tile/",
"http://online3.map.bdimg.com/tile/",
"http://online4.map.bdimg.com/tile/" ];
function getTilesUrl(xy, z) {
var x = xy.x;
var y = xy.y;
var udt = "20150518";
var style = "pl";
// if (this.map.highResolutionEnabled()) {
//style = "ph"
// }
var cM = j[Math.abs(x + y) % j.length] + "?qt=tile&x="
+ (x + "").replace(/-/gi, "M") + "&y="
+ (y + "").replace(/-/gi, "M") + "&z=" + z + "&styles=" + style
+ "&udt=" + udt;
// 这个地方废弃了上面的计算结果，直接采用本地图片
//cM = "maptile/" + z + "/" + x + "/" + y + ".jpg";
return cM.replace(/-(\d+)/gi, "M$1")
}
return function(map, callback){findAllTiles(map, callback);};
}然后引入这个js文件，再写个按钮，不断的移动窗口，添加新的下载连接吧。
<script type="text/javascript" src="js/findtiles.js"></script>
<input type="button" value="findtiles" onclick="findtiles();">
<script>
function findtiles(){
var findAllTiles = downloadBaiduTiles();
findAllTiles(map, addUrls);
}
function addUrls(xyz, url){
var div = document.getElementById("list");
var anchor = document.createElement("a");
anchor.href = url;
anchor.innerHTML = xyz[2]+"/"+xyz[0]+"/"+xyz[1];
div.appendChild(anchor);
var br = document.createElement("br");
div.appendChild(br);
}
</script>效果图：
这个方式有个优点，可以随时缩放地图，然后点击按钮，这样就可以不断的获取新的瓦片地址了。不过代码没有优化，移动地图的时候可能产生重复的瓦片，然后下载程序还没有写。最后根据xyz来安排文件放置位置就可以了。