恩,我想大家都懂的,本页代码源自Mapbar的Api,研究了一下它的绘制地图的算法,其实上篇文章《抓取Mapbar地图切片的一个算法》就是根据Mapbar绘制地图的算法得来的,那么今天就分享一下Mapbar绘制地图的算法。在这之前,大家可以先看一下我制作的一个Demo:mapbar.html。
下面就是给力的源代码了,可能用到了一小点的jQuery。
var divId = 'map';
var imgWidth = 300;
var imgHeight = 300;
var imgExt = 'png';
var centerpoint = '120.15689,35.96333';
var point = centerpoint.split(',');
var _centerLon = point[0];
var _centerLat = point[1];
var zoomlevel = 8;
var $map = $('#'+divId);
//每层地图切片的文件夹名称
var levelFolder = new Array('W','0','1','2','3','4','5','6','7','8','9','10','11','12','13','16');
//每层地图切片所跨的经度数
var cutImgLonRange = new Array(90,40,20,10,5,2,1,0.5,0.2,0.1,0.05,0.02,0.01,0.005,0.002,0.001);
//每层地图切片所跨的维度数
var cutImgLatRange = new Array(90*0.8,40*0.8,20*0.8,10*0.8,5*0.8,2*0.8,0.8,0.5*0.8,0.2*0.8,0.1*0.8,0.05*0.8,0.02*0.8,0.01*0.8,0.005*0.8,0.002*0.8,0.001*0.8);
//地图区块大小 将不同区块的放在不同的文件夹下面进行管理
var blockSize = new Array(10,10,10,10,10,10,10,10,10,10,50,50,50,50,50,50);
//纬度的偏移
var latOffset = new Array(0,0,0,0,0,0,0,0,75,0,0,-150,0,0,0,0);
function drawMap(){
var LatLon = coordOffsetDecrypt(_centerLon,_centerLat);//解密Mapbar坐标
centerLon = LatLon[0];
centerLat = LatLon[1];
var mapwidth = $map.width();
var mapheight = $map.height();
var halfNum5clipX = Math.ceil(mapwidth/imgWidth/2);
var halfNum5clipY = Math.ceil(mapheight/imgHeight/2);
var _blockSize = blockSize[zoomlevel];
var clipLonRange = cutImgLonRange[zoomlevel];
var clipLatRange = cutImgLatRange[zoomlevel];
var multiple = 100000;
clipNo5X=Math.floor((centerLon)/clipLonRange);
clipNo5Y=Math.floor((centerLat)/clipLatRange);
if(clipNo5X<0)clipNo5X+=1;
var mapX=mapwidth/2-Math.round(((centerLon*multiple)%(clipLonRange*multiple))*imgWidth/(clipLonRange*multiple));
if(centerLat>=0) {
mapY=mapheight/2-imgHeight+Math.round(((centerLat*multiple)%(clipLatRange*multiple))*imgHeight/(clipLatRange*multiple));
}else {
mapY=mapheight/2+Math.round(((centerLat*multiple)%(clipLatRange*multiple))*imgHeight/(clipLatRange*multiple));
}
var clipXNum=(360/clipLonRange);
rotationCosVal=1.0;
rotationSinVal=0.0;
var Clip = [];
clipNo5X=Math.floor((centerLon)/clipLonRange);
clipNo5Y=Math.floor((centerLat)/clipLatRange);
if(clipNo5X<0)clipNo5X+=1;
var mapX=mapwidth/2-Math.round(((centerLon*multiple)%(clipLonRange*multiple))*imgWidth/(clipLonRange*multiple));
if(centerLat>=0) {
mapY=mapheight/2-imgHeight+Math.round(((centerLat*multiple)%(clipLatRange*multiple))*imgHeight/(clipLatRange*multiple));
}else {
mapY=mapheight/2+Math.round(((centerLat*multiple)%(clipLatRange*multiple))*imgHeight/(clipLatRange*multiple));
}
$map.html('');
// -- 真正给力的开始
for (var _clipXNo = -halfNum5clipX - 1; _clipXNo <= halfNum5clipX; _clipXNo++) {
for (var _clipYNo = -halfNum5clipY - 1; _clipYNo <= halfNum5clipY; _clipYNo++) {
try {
var clipXNo = parseInt(clipNo5X + _clipXNo);//地图横向切片序列号
var clipYNo = parseInt(clipNo5Y + _clipYNo);
clipXNo = (clipXNo) % clipXNum
if (clipXNo >= (clipXNum / 2))
clipXNo -= clipXNum;
if (clipXNo < (-clipXNum / 2))
clipXNo += clipXNum;
var folderX = parseInt(Math.floor((clipXNo) / _blockSize));
var folderY = parseInt(Math.floor((clipYNo) / _blockSize));
if (folderX < 0)
folderX += 1;
if (folderY < 0)
folderY += 1;
var fileXNo = (clipXNo) - folderX * _blockSize;
var fileYNo = (clipYNo) - folderY * _blockSize;
var _strImgUrl = 'http://img.mapbar.com/maplite/mapbank/mapbar/' + levelFolder[zoomlevel] + '/';
if (zoomlevel >= 14)
_strImgUrl += folderX + "/";
_strImgUrl += folderX + "_" + folderY + "/";
_strImgUrl += fileXNo + "_" + fileYNo + "." + imgExt;
var clipLeft = (_clipXNo * imgWidth) + parseInt(mapX);
var clipTop = (-(_clipYNo * imgHeight) + parseInt(mapY));
clipTop = clipTop + latOffset[zoomlevel];
var isClearImgUrl = false;
if ((clipLeft < -imgWidth || clipLeft > mapwidth || clipTop > mapheight || clipTop < -imgHeight))
isClearImgUrl = true;
if (isClearImgUrl)
continue;
var clipId = ((zoomlevel).toString(16) + (clipNo5X + _clipXNo).toString(16) + 'l' + (clipNo5Y + _clipYNo).toString(16)).toLowerCase();
if (_strImgUrl && _strImgUrl.indexOf("NaN") < 0) {
if (Clip[clipId] == null) {
Clip[clipId] = new Image();
Clip[clipId].id = clipId;
Clip[clipId].name = clipId;
Clip[clipId].unselectable = "on";
Clip[clipId].style.position = "absolute";
Clip[clipId].style.MozUserSelect = "none";
Clip[clipId].src = _strImgUrl;
}
var p2 = (clipLeft + imgWidth / 2 - mapwidth / 2) * rotationCosVal - (clipTop + imgHeight / 2 - mapheight / 2) * rotationSinVal + mapwidth / 2;
var p5 = (clipLeft + imgWidth / 2 - mapwidth / 2) * rotationSinVal + (clipTop + imgHeight / 2 - mapheight / 2) * rotationCosVal + mapheight / 2;
Clip[clipId].style.top = parseInt(p5 - imgHeight / 2) + "px";
Clip[clipId].style.left = parseInt(p2 - imgWidth / 2) + "px";
//var interval = parseInt($('#interval').val());
$map.append(Clip[clipId]);
}
_strImgUrl = null;
}
catch (e) {
throw (e);
}
}
}
}
// The follow is two helper functions
/**
* 将真实地理坐标加密为Mapbar经纬度坐标
*
* @param x 经度值
* @param y 维度值
* @returns [x,y]
*/
function coordOffsetEncrypt(x,y){
x = parseFloat(x)*100000%36000000;
y = parseFloat(y)*100000%36000000;
_X = parseInt(((Math.cos(y/100000))*(x/18000))+((Math.sin(x/100000))*(y/9000))+x);
_Y = parseInt(((Math.sin(y/100000))*(x/18000))+((Math.cos(x/100000))*(y/9000))+y);
return [_X/100000.0,_Y/100000.0];
}
/**
* 将Mapbar经纬坐标解密为真实地理坐标
*
* @param x 经度值
* @param y 维度值
* @returns [x,y]
*/
function coordOffsetDecrypt(x,y){
x = parseFloat(x)*100000%36000000;
y = parseFloat(y)*100000%36000000;
x1 = parseInt(-(((Math.cos(y/100000))*(x/18000))+((Math.sin(x/100000))*(y/9000)))+x);
y1 = parseInt(-(((Math.sin(y/100000))*(x/18000))+((Math.cos(x/100000))*(y/9000)))+y);
x2 = parseInt(-(((Math.cos(y1/100000))*(x1/18000))+((Math.sin(x1/100000))*(y1/9000)))+x+((x>0)?1:-1));
y2 = parseInt(-(((Math.sin(y1/100000))*(x1/18000))+((Math.cos(x1/100000))*(y1/9000)))+y+((y>0)?1:-1));
return [x2/100000.0,y2/100000.0];
}
本代码不到200行,可谓是言简意赅,童叟无欺,欢迎拍砖。
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学习了
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