根据地理坐标计算瓦片行列号

##http://jsfiddle.net/84P9r/

$(document).ready(function(){
    url = "http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
    var map = L.map('map').setView([0, 0], 0);

    if (typeof(Number.prototype.toRad) === "undefined") {
      Number.prototype.toRad = function() {
        return this * Math.PI / 180;
      }
    }


    function getTileURL(lat, lon, zoom) {
        var xtile = parseInt(Math.floor( (lon + 180) / 360 * (1<<zoom) ));
        var ytile = parseInt(Math.floor( (1 - Math.log(Math.tan(lat.toRad()) + 1 / Math.cos(lat.toRad())) / Math.PI) / 2 * (1<<zoom) ));
        return "" + zoom + "/" + xtile + "/" + ytile;
    }
    


    L.tileLayer(url, {
        maxZoom: 18
    }).addTo(map);

    map.on('click', function (e) {
        url = getTileURL(e.latlng.lat, e.latlng.lng, map.getZoom())
        console.log(url);
        alert(url);
    });