Synthetic Points

This example uses OpenLayers v4.0.1. The latest is v.

#### Synthetic Points

Synthetic points example.

Related API documentation:

- ol.Feature
,
- ol.Map
,
- ol.View
,
- ol.geom.LineString
,
- ol.geom.Point
,
- ol.layer.Vector
,
- ol.source.Vector
,
- ol.style.Circle
,
- ol.style.Fill
,
- ol.style.Stroke
,
- ol.style.Style

Copy Edit
Synthetic Points Synthetic points example. 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 = ''; } }); <div id="map" class="map"></div>

    <!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>