Ch. 7, Fig. 2 - D3.js in Action

This is the code for Chapter 7, Figure 2 from D3.js in Action showing a hand-crafted GeoJSON object representing the bounding box of Manhatten on a D3 tile map.

The purpose of this figure is to better understand the GeoJSON format, not tile mapping, which is explained in detail later in the chapter.

<html>
<head>
  <title>D3 in Action Chapter 7 - Example 11</title>
  <meta charset="utf-8" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script src="tile.js" type="text/JavaScript"></script>
</head>
<style>
  svg {
    height: 500px;
    width: 500px;
    border: 1px solid gray;
  }
  
  .countries {
    fill: red;
    fill-opacity: .5;
    stroke: black;
    stroke-width: 1px;
  }

</style>
<body>

<div id="viz">
  <svg>
  </svg>
</div>
<div id="controls" />
</body>
  <footer>
    
<script>
  
  var manhattenBoundingBox = {geometry: {coordinates: [[[-74.0479, 40.8820], [-73.9067, 40.8820], [-73.9067, 40.6829], [-74.0479, 40.6829], [-74.0479, 40.8820]]], type: "Polygon"}, id: 999999, properties:{}, type: "Feature"};

var width = 500,
    height = 500;
    
  d3.select("svg").append("g").attr("id", "tiles");
  d3.select("svg").append("g").attr("id", "vectors");

var tile = d3.geo.tile()
    .size([width, height]);

var projection = d3.geo.mercator()
    .scale((1 << 18) / 2 / Math.PI)
    .translate([width / 2, height / 2]);

var center = projection([-73.95, 40.7]);

var path = d3.geo.path()
    .projection(projection);

var zoom = d3.behavior.zoom()
    .scale(projection.scale() * 2 * Math.PI)
    .translate([width - center[0], height - center[1]])
    .on("zoom", redraw);

d3.select("svg").call(zoom);
projection
    .scale(1 / 2 / Math.PI)
    .translate([0, 0]);
    
    geoPath = d3.geo.path().projection(projection);
    
    d3.select("#vectors").selectAll("path.countries").data([manhattenBoundingBox])
    .enter()
    .append("path")
    .attr("d", geoPath)
    .attr("class", "countries")
    .style("fill", "red")
    .style("stroke-width", 3)
    .style("stroke", "black")
    .style("fill-opacity", .25)

redraw();

function redraw() {
      var tiles = tile
      .scale(zoom.scale())
      .translate(zoom.translate())
      ();
      
      var image = d3.select("#tiles").attr("transform", "scale(" + tiles.scale + ")translate(" + tiles.translate + ")")
    .selectAll("image")
      .data(tiles, function(d) { return d; });

image.exit()
      .remove();

image.enter().append("image")
      .attr("xlink:href", function(d) { return "https://" + ["a", "b", "c", "d"][Math.random() * 4 | 0] + ".tiles.mapbox.com/v3/examples.map-zgrqqx0w/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
      .attr("width", 1)
      .attr("height", 1)
      .attr("x", function(d) { return d[0]; })
      .attr("y", function(d) { return d[1]; });
      
      projection
      .scale(zoom.scale() / 2 / Math.PI)
      .translate(zoom.translate());

d3.selectAll("path")
      .attr("d", geoPath);
  }
</script>
  </footer>

</html>

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