OpenLayers示例代码：合成点
OpenLayers示例代码：合成点
<!DOCTYPE html>
<html>
<head>
<title>Synthetic Points</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>
</head>
<body>
<div id="map" class="map"></div>
<script>
var count = 20000;
var features = new Array(count);
var e = 18000000;
for (var i = 0; i < count; ++i) {
features[i] = new ol.Feature({
'geometry': new ol.geom.Point(
[2 * e * Math.random() - e, 2 * e * Math.random() - e]),
'i': i,
'size': i % 2 ? 10 : 20
});
}
var styles = {
'10': new ol.style.Style({
image: new ol.style.Circle({
radius: 5,
fill: new ol.style.Fill({color: '#666666'}),
stroke: new ol.style.Stroke({color: '#bada55', width: 1})
})
}),
'20': new ol.style.Style({
image: new ol.style.Circle({
radius: 10,
fill: new ol.style.Fill({color: '#666666'}),
stroke: new ol.style.Stroke({color: '#bada55', width: 1})
})
})
};
var vectorSource = new ol.source.Vector({
features: features,
wrapX: false
});
var vector = new ol.layer.Vector({
source: vectorSource,
style: function(feature) {
return styles[feature.get('size')];
}
});
var map = new ol.Map({
layers: [vector],
target: document.getElementById('map'),
view: new ol.View({
center: [0, 0],
zoom: 2
})
});
var point = null;
var line = null;
var displaySnap = function(coordinate) {
var closestFeature = vectorSource.getClosestFeatureToCoordinate(coordinate);
if (closestFeature === null) {
point = null;
line = null;
} else {
var geometry = closestFeature.getGeometry();
var closestPoint = geometry.getClosestPoint(coordinate);
if (point === null) {
point = new ol.geom.Point(closestPoint);
} else {
point.setCoordinates(closestPoint);
}
if (line === null) {
line = new ol.geom.LineString([coordinate, closestPoint]);
} else {
line.setCoordinates([coordinate, closestPoint]);
}
}
map.render();
};
map.on('pointermove', function(evt) {
if (evt.dragging) {
return;
}
var coordinate = map.getEventCoordinate(evt.originalEvent);
displaySnap(coordinate);
});
map.on('click', function(evt) {
displaySnap(evt.coordinate);
});
var stroke = new ol.style.Stroke({
color: 'rgba(255,255,0,0.9)',
width: 3
});
var style = new ol.style.Style({
stroke: stroke,
image: new ol.style.Circle({
radius: 10,
stroke: stroke
})
});
map.on('postcompose', function(evt) {
var vectorContext = evt.vectorContext;
vectorContext.setStyle(style);
if (point !== null) {
vectorContext.drawGeometry(point);
}
if (line !== null) {
vectorContext.drawGeometry(line);
}
});
map.on('pointermove', function(evt) {
if (evt.dragging) {
return;
}
var pixel = map.getEventPixel(evt.originalEvent);
var hit = map.hasFeatureAtPixel(pixel);
if (hit) {
map.getTarget().style.cursor = 'pointer';
} else {
map.getTarget().style.cursor = '';
}
});
</script>
</body>
</html>
说明：
OpenLayers示例代码：合成点
