通过经纬度获取中心点,以及绑定的缩放级别

//根据经纬度的距离获取地图的缩放级
function getRoom(diff){
	var room =    new Array(0,  1,  2, 3, 4, 5, 6,7,8,  9,   10,  11,  12,  13, 14);
	var diffArr = new Array(360,180,90,45,22,11,5,2.5,1.25,0.6,0.3,0.15,0.07,0.03,0);
	for(var i = 0; i < diffArr.length; i ++){
		if((diff - diffArr[i]) >= 0){
			return room[i];
		}
	}	
	return 14;
}


function getCenterPoint(maxJ,minJ,maxW,minW){//通过经纬度获取中心位置和缩放级别
	if(maxJ==minJ&&maxW==minW)return [maxJ,maxW,0];
	var diff = maxJ - minJ;
	if(diff < (maxW - minW))diff = maxW - minW;
	diff = parseInt(10000 * diff)/10000;	
	var centerJ = minJ*1000000+1000000*(maxJ - minJ)/2;
	var centerW = minW*1000000+1000000*(maxW - minW)/2;
         var zoom = getRoom(diff);
	return [centerJ/1000000,centerW/1000000,zoom];
}