[置顶] Mapbar地图切片的抓取和拼接算法

1.MapBar 地图瓦片抓取算法

此地图瓦片抓取算法是根据Mapbarapi里的绘图算法写出来的，使用PHP编写，将代码保存为一个PHP文件后，然后使用命令行运行: $ php -f filename.php。

注：cmd>cd "x:\...\php.exe"。

<?php
/**
 * 抓取mapbar切片的算法 by CrossYou at 2011/01/22
 *
 * @version 1.0.0
 * @link	http://crossyou.cn/
 */
$mapbarImgRoot = './mapbar/';

//每层地图切片的文件夹名称
$levelFolder = 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
$cutImgLonRange=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
$cutImgLatRange=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);

$blockSize=array(10,10,10,10,10,10,10,10,10,10,50,50,50,50,50,50);

for($zoomLevel=0;$zoomLevel<16;$zoomLevel++){

	$clipXNum=ceil(360/$cutImgLonRange[$zoomLevel]);
	$clipYNum=ceil(90/$cutImgLatRange[$zoomLevel]);

	$clipLonRange = $cutImgLonRange[$zoomLevel];
	$clipLatRange = $cutImgLatRange[$zoomLevel];

	$clipXGap = -180-$clipLonRange/2;

	//从缩放级别5开始，只抓取中国范围内的地图，因为此级别以后的，非国内的都是背景图，抓了无意义。
	if($zoomLevel>3){

		//--------中国范围的地图
		$west = 73;
		$east = 136;
		$north = 54;
		$south = 3;

		$chinaLonRange = 63;//中国经度跨度
		$chinaLatRange = 51;//中国维度跨度

		$chinaClipXNum = ceil($chinaLonRange/$clipLonRange);
		$chinaClipYNum = ceil($chinaLatRange/$clipLatRange);

		for($i=0;$i<$chinaClipXNum;$i++){
			$lon = $west+$clipLonRange*$i;

			for($j=0;$j<$chinaClipYNum;$j++){
				$lat = $south+$clipLatRange*$j;

				$clipXNo =  floor($lon/$cutImgLonRange[$zoomLevel]);
				$clipYNo =  floor($lat/$cutImgLatRange[$zoomLevel]);

				$clipXNo=($clipXNo)%$clipXNum;
				if($clipXNo>=$clipXNum/2)$clipXNo-=$clipXNum;
				if($clipXNo<-$clipXNum/2)$clipXNo+=$clipXNum;

				echo "\n新的切片... => \n";
				echo '经纬度：'.$lon.' , '.$lat."\n";
				echo "-------------------------------\n";
				echo '切片序号：'.$clipXNo.' , '.$clipYNo."\n";
				echo "-------------------------------\n";

				//切片分文件夹存放位置
				$folderXNo = (int)floor($clipXNo/$blockSize[$zoomLevel]);
				//切片分文件夹存放位置
				$folderYNo = (int)floor($clipYNo/$blockSize[$zoomLevel]);

				if($folderXNo<0){
					$folderXNo+=1;
				}

				if($folderYNo<0){
					$folderYNo+=1;
				}

				$fileXNo =($clipXNo)-$folderXNo*$blockSize[$zoomLevel];
				$fileYNo =($clipYNo)-$folderYNo*$blockSize[$zoomLevel]; 

				$imgPre = 'http://img.mapbar.com/maplite/mapbank/mapbar/';

				$imgDir = $levelFolder[$zoomLevel].'/'.$folderXNo.'_'.$folderYNo.'/';
				$imgName = $fileXNo.'_'.$fileYNo.'.png';
				$imgUrl = $imgPre.$imgDir.$imgName;
				$localImgDir = $mapbarImgRoot.$imgDir;

				$localImgName = $localImgDir.$imgName;
				if (!is_file($localImgName)){
					createdir($localImgDir);
					if(copy($imgUrl,$localImgName)){
						echo '图片:=> '.$imgDir.$imgName." 成功下载到本地\n\n";
					}
				}
			}
		}
	}else{
		for($i= -$clipXNum/2;$i<=$clipXNum/2;$i++){
			$lon = $clipLonRange*$i;
			if($i<0)$lon+=$clipLonRange/2;
			if($i==0)continue;
			if($i>0)$lon-=$clipLonRange/2;

			for($j=-$clipYNum;$j<=$clipYNum;$j++){

				$lat = $clipLatRange*$j;

				if($j<0)$lat+=$clipLatRange/2;
				if($j==0)continue;
				if($j>0)$lat-=$clipLatRange/2;

				$clipXNo =  floor($lon/$cutImgLonRange[$zoomLevel]);
				$clipYNo =  floor($lat/$cutImgLatRange[$zoomLevel]);

				$clipXNo=($clipXNo)%$clipXNum;
				if($clipXNo>=$clipXNum/2)$clipXNo-=$clipXNum;
				if($clipXNo<-$clipXNum/2)$clipXNo+=$clipXNum;

				echo "\n新的切片... => \n";
				echo '经纬度：'.$lon.' , '.$lat."\n";
				echo "-------------------------------\n";
				echo '切片序号：'.$clipXNo.' , '.$clipYNo."\n";
				echo "-------------------------------\n";

				//切片分文件夹存放位置
				$folderXNo = (int)floor($clipXNo/$blockSize[$zoomLevel]);
				//切片分文件夹存放位置
				$folderYNo = (int)floor($clipYNo/$blockSize[$zoomLevel]);

				if($folderXNo<0){
					$folderXNo+=1;
				}

				if($folderYNo<0){
					$folderYNo+=1;
				}

				$fileXNo =($clipXNo)-$folderXNo*$blockSize[$zoomLevel];
				$fileYNo =($clipYNo)-$folderYNo*$blockSize[$zoomLevel]; 

				$imgPre = 'http://img.mapbar.com/maplite/mapbank/mapbar/';

				$imgDir = $levelFolder[$zoomLevel].'/'.$folderXNo.'_'.$folderYNo.'/';
				$imgName = $fileXNo.'_'.$fileYNo.'.png';
				$imgUrl = $imgPre.$imgDir.$imgName;
				$localImgDir = $mapbarImgRoot.$imgDir;

				$localImgName = $localImgDir.$imgName;
				if (!is_file($localImgName)){
					createdir($localImgDir);
					if(copy($imgUrl,$localImgName)){
						echo '图片:=> '.$imgDir.$imgName." 成功下载到本地\n\n";
					}
				}

			}
		}
	}
}

/**
 * 创建多级目录 摘自网络
 * 如有好的建议，请到 http://crossyou.cn/给我留言 谢谢！
 *
 * @since 1.0.5
 * @param string $dir
 */
function createdir($dir){

	$array_dir=explode("/",$dir);//把多级目录分别放到数组中

	$depth = count($array_dir);
	$path = '';
	for($i=0;$i<$depth;$i++){

		$path .= $array_dir[$i]."/";

		if(!is_dir($path)){
			mkdir($path);
		}
	}
}
?>

2.MapBar地图瓦片拼接算法

作者制作的一个Demo：http://www.crossyou.cn/attachments/2011/03/mapbar.html。下面的源代码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;

	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];
}

 

原文出自 CrossYou'Blog ：

抓取算法：http://www.crossyou.cn/an-algorithm-to-crawl-mapbar-map.htm 

瓦片拼接算法：http://www.crossyou.cn/a-simple-map-of-the-source-code-mapbar.htm

注：以上内容仅供学习，在此严重感谢作者分享。

后记：经验证，百度使用的MapBar的地图，算法相同，其url前缀为：

 http://img.mapbar.com/maplite/mapbank/baidu/