概述：
在前文中分别讲到了在Arcgis for js、Openlayers2中去加载天地图，同时也讲到了天地图的离线加载方式。在本文，讲述在Openlayers3中实现在线/离线的天地图的加载。
实现：
直接贴代码吧，效果就不贴了：
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>TDT</title>
<link rel="stylesheet" type="text/css" href="../../../../plugin/ol3/css/ol.css"/>
<style type="text/css">
body, #map {
border: 0px;
margin: 0px;
padding: 0px;
100%;
height: 100%;
font-size: 13px;
}
#map{
background: url("../../images/bgImg.gif");
background-repeat: inherit;
}
</style>
<script type="text/javascript" src="../../../../plugin/ol3/build/ol-debug.js"></script>
<script type="text/javascript" src="../../../../plugin/jquery/jquery-1.8.3.js"></script>
<script type="text/javascript">
var map;
function init(){
var bounds = [73.4510046356223, 18.1632471876417,
134.976797646506, 53.5319431522236];
var projection = new ol.proj.Projection({
code: 'EPSG:4326',
units: 'degrees'
});
var vec_c = getTdtLayer("vec_c");
var cva_c = getTdtLayer("cva_c");
var wms = new ol.layer.Image({
source: new ol.source.ImageWMS({
ratio: 1,
url: 'http://localhost:8088/geoserver/lzugis/wms',
params: {
'FORMAT': 'image/png',
'VERSION': '1.1.1',
LAYERS: 'lzugis:capital',
STYLES: ''
}
})
});
var map = new ol.Map({
controls: ol.control.defaults({
attribution: false
}),
target: 'map',
layers: [vec_c,cva_c,wms],
view: new ol.View({
projection: projection,
minZoom:2,
maxZoom:8
})
});
map.getView().fitExtent(bounds, map.getSize());
}
function getTdtLayer(lyr){
var url = "http://localhost:8081/lzugis/tdttile?T="+lyr+"&X={x}&Y={y}&L={z}";
// var url = "http://t0.tianditu.com/DataServer?T="+lyr+"&X={x}&Y={y}&L={z}";在线
var projection = ol.proj.get("EPSG:4326");
var projectionExtent = [ -180, -90, 180, 90 ];
var maxResolution = (ol.extent.getWidth(projectionExtent) / (256 * 2));
var resolutions = new Array(16);
var z;
for (z = 0; z < 16; ++z) {
resolutions[z] = maxResolution / Math.pow(2, z);
}
var tileOrigin = ol.extent.getTopLeft(projectionExtent);
var layer = new ol.layer.Tile({
extent: [ -180, -90, 180, 90 ],
source: new ol.source.TileImage({
tileUrlFunction: function(tileCoord) {
var z = tileCoord[0]+1;
var x = tileCoord[1];
var y = -tileCoord[2]-1;
var n = Math.pow(2, z + 1);
x = x % n;
if (x * n < 0) {
x = x + n;
}
return url.replace('{z}', z.toString())
.replace('{y}', y.toString())
.replace('{x}', x.toString());
},
projection: projection,
tileGrid: new ol.tilegrid.TileGrid({
origin: tileOrigin,
resolutions: resolutions,
tileSize: 256
})
})
});
return layer;
}
</script>
</head>
<body onLoad="init()">
<div id="map">
</div>
</body>
</html>