OpenLayers示例代码：geojson-vt集成
OpenLayers示例代码：geojson-vt集成
<!DOCTYPE html>
<html>
<head>
<title>geojson-vt integration</title>
<link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css">
<!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
<script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script>
<script src="https://mapbox.github.io/geojson-vt/geojson-vt-dev.js"></script>
</head>
<body>
<div id="map" class="map"></div>
<script>
var replacer = function(key, value) {
if (value.geometry) {
var type;
var rawType = value.type;
var geometry = value.geometry;
if (rawType === 1) {
type = geometry.length === 1 ? 'Point' : 'MultiPoint';
} else if (rawType === 2) {
type = geometry.length === 1 ? 'LineString' : 'MultiLineString';
} else if (rawType === 3) {
type = geometry.length === 1 ? 'Polygon' : 'MultiPolygon';
}
return {
'type': 'Feature',
'geometry': {
'type': type,
'coordinates': geometry.length == 1 ? geometry : [geometry]
},
'properties': value.tags
};
} else {
return value;
}
};
var tilePixels = new ol.proj.Projection({
code: 'TILE_PIXELS',
units: 'tile-pixels'
});
var map = new ol.Map({
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
target: 'map',
view: new ol.View({
center: [0, 0],
zoom: 2
})
});
var url = 'https://openlayers.org/en/v4.0.1/examples/data/geojson/countries.geojson';
fetch(url).then(function(response) {
return response.json();
}).then(function(json) {
var tileIndex = geojsonvt(json, {
extent: 4096,
debug: 1
});
var vectorSource = new ol.source.VectorTile({
format: new ol.format.GeoJSON(),
tileGrid: ol.tilegrid.createXYZ(),
tilePixelRatio: 16,
tileLoadFunction: function(tile) {
var format = tile.getFormat();
var tileCoord = tile.getTileCoord();
var data = tileIndex.getTile(tileCoord[0], tileCoord[1], -tileCoord[2] - 1);
var features = format.readFeatures(
JSON.stringify({
type: 'FeatureCollection',
features: data ? data.features : []
}, replacer));
tile.setLoader(function() {
tile.setFeatures(features);
tile.setProjection(tilePixels);
});
},
url: 'data:' // arbitrary url, we don't use it in the tileLoadFunction
});
var vectorLayer = new ol.layer.VectorTile({
source: vectorSource
});
map.addLayer(vectorLayer);
});
</script>
</body>
</html>
说明：
OpenLayers示例代码：geojson-vt集成
