Layer's globalCompositeOperation
index.html
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<html>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Layer - Layer&#x27;s globalCompositeOperation</title>
  <style type="text/css">
    html,body{margin:0px;height:100%;width:100%}
    .container{width:100%;height:100%}
  </style>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/maptalks.css">
  <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/[email protected]/dist/maptalks.min.js"></script>
  <body>

    <div id="map" class="container"></div>

    <script>
      var map = new maptalks.Map('map', {
        center: [-0.113049,51.498568],
        zoom: 14,
        baseLayer: new maptalks.TileLayer('base', {
          urlTemplate: 'http://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png',
          subdomains: ['a','b','c','d'],
          attribution: '&copy; <a href="http://osm.org">OpenStreetMap</a> contributors, &copy; <a href="https://carto.com/">CARTO</a>'
        })
      });

      //globalCompositeOperation on MDN:
      //https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/globalCompositeOperation
      var layer = new maptalks.VectorLayer('v', { globalCompositeOperation : 'difference' }).addTo(map);

      //prepare data
      var center = map.getCenter(), width = 0.055, height = 0.03,
        markers = [],
        colors = ['#f00', '#0f0', '#00f'];
      for (var i = 0; i <= 50; i++) {
        var x = center.x + (Math.random() - 0.5) * width * 0.5;
        var y = center.y + (Math.random() - 0.5) * height * 0.5;
        var color = colors[Math.floor(Math.random() * 3)];
        markers.push(new maptalks.Marker([x, y], {
          'symbol' : {
            'markerType' : 'ellipse',
            'markerFill' : color,
            'markerFillOpacity' : 1,
            'markerLineWidth' : 1,
            'markerLineColor' : color,
            'markerWidth' : 70,
            'markerHeight' : 70
          }
        }));
      }
      layer.addGeometry(markers);

    </script>
  </body>
</html>
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