georaster-layer-for-leaflet-example/examples/wind-direction-arrows.html at master · GeoTIFF/georaster-layer-for-leaflet-example · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css"/>
    <style>
      #map {
        bottom: 0;
        left: 0;
        position: absolute;
        right: 0;
        top: 0;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script src="https://unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>
    <script src="https://unpkg.com/georaster"></script>
    <script src="https://unpkg.com/georaster-layer-for-leaflet"></script>
    <script>
      // initalize leaflet map
      var map = L.map('map').setView([0, 0], 5);

      // add OpenStreetMap basemap
      L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
          attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
      }).addTo(map);

      var url_to_geotiff_file = "https://georaster-layer-for-leaflet.s3.amazonaws.com/wind_direction.tif";

      fetch(url_to_geotiff_file)
        .then(response => response.arrayBuffer())
        .then(arrayBuffer => {
          parseGeoraster(arrayBuffer).then(georaster => {
            var layer = new GeoRasterLayer({
              georaster,
              customDrawFunction: function({ context, x, y, width, height, values }) {
                // from https://github.com/stuartmatthews/leaflet-geotiff/blob/master/leaflet-geotiff-vector-arrows.js
                var value = values[0];
                var arrowSize = width / 2.5;
                context.save();
                context.translate(x, y);
      					context.rotate((90+value)*Math.PI/180);
      					context.beginPath();
      					context.moveTo(-arrowSize/2, 0);
      					context.lineTo(+arrowSize/2, 0);
      					context.moveTo(arrowSize*0.25, -arrowSize*0.25);
      					context.lineTo(+arrowSize/2, 0);
      					context.lineTo(arrowSize*0.25, arrowSize*0.25);
      					context.stroke();
      					context.restore();
              }
            });
            layer.addTo(map);
            map.fitBounds(layer.getBounds());
        });
      });
    </script>
  </body>
</html>