一份最简单的Mapbar地图源代码 | Sobird

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：http://bcs./word-press/2011/03/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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