抓取Mapbar地图切片的一个算法

抓取Mapbar地图切片的一个算法

发表于 2011/03/26

这个算法去年的时候就写了，自己就是抓着玩，也算是验证了这个算法的可行性，今天特向大家分享一下，主要是根据Mapbarapi里的绘图算法写出来的，实在没什么技术含量。

有想玩的同学可以试试，不过因此引起的后果本人概不负责，请慎重啊！

算法使用PHP写的，将下面代码保存为一个PHP文件后在终端运行: $ php -f filename.php一下就可以了。

代码如下：

/**
* 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);
}
}
}

《全文完》