WWSD #15: Mapbox-gl + d3 canvas overlay

Working with spatial data

Example #15

Rendering to a Canvas overlay with d3.js on top of Mapbox-gl

Built with blockbuilder.org

forked from enjalot's block: dots on a map: setup-gl

forked from enjalot's block: WWSD #11: Mapbox-gl + d3 overlay

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
  <script src="//d3js.org/topojson.v1.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js'></script>
  <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.css' rel='stylesheet' />

<body>
  <div id="map"></div>
  <script>
  
    mapboxgl.accessToken = 'pk.eyJ1IjoiZW5qYWxvdCIsImEiOiJjaWhtdmxhNTIwb25zdHBsejk0NGdhODJhIn0.2-F2hS_oTZenAWc0BMf_uw'
    
    //Setup mapbox-gl map
    var map = new mapboxgl.Map({
      container: 'map', // container id
      style: 'mapbox://styles/enjalot/cihmvv7kg004v91kn22zjptsc',
      center: [-0.1,51.5119112],
      zoom: 10.5,
      
    })
    map.scrollZoom.disable()
    map.addControl(new mapboxgl.Navigation());

var bbox = document.body.getBoundingClientRect();
    var width = bbox.width;
    var height = bbox.height
    // Setup our svg layer that we can manipulate with d3
    var container = map.getCanvasContainer()
    
    var canvas = d3.select(container).append("canvas").node()
    canvas.width = width;
    canvas.height = height
    var ctx = canvas.getContext('2d')
    // we calculate the scale given mapbox state (derived from viewport-mercator-project's code)
    // to define a d3 projection
    function getD3() {
      var bbox = document.body.getBoundingClientRect();
      var center = map.getCenter();
      var zoom = map.getZoom();
      // 512 is hardcoded tile size, might need to be 256 or changed to suit your map config
      var scale = (512) * 0.5 / Math.PI * Math.pow(2, zoom);

var d3projection = d3.geo.mercator()
        .center([center.lng, center.lat])
        .translate([bbox.width/2, bbox.height/2])
        .scale(scale);

return d3projection;
    }
    // calculate the original d3 projection
    var d3Projection = getD3();
    
    var path = d3.geo.path()
  
    var url = "https://enjalot.github.io/wwsd/data/UK/london_stations.topojson";
    d3.json(url, function(err, data) {
      var points = topojson.feature(data, data.objects.london_stations)
      //console.log(data[0], getLL(data[0]), project(data[0]))
      
      
      
      function render() {
        d3Projection = getD3();
        path.projection(d3Projection)
        ctx.clearRect(0, 0, width, height)
        
        ctx.fillStyle = "#0082a3";
        ctx.strokeStyle = "#004d60"
        points.features.forEach(function(d) {
          var p = d3Projection(d.geometry.coordinates)
          ctx.beginPath()
          ctx.arc(p[0], p[1], 6, 0, Math.PI*2)
          ctx.fill()
          ctx.stroke()
        })
        
      }

// re-render our visualization whenever the view changes
      map.on("viewreset", function() {
        render()
      })
      map.on("move", function() {
        render()
      })

// render our initial visualization
      render()
    })

</script>
</body>

https://d3js.org/topojson.v1.min.js

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js

https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js