D3 Examples - Overhead Voronoi

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<!DOCTYPE html>
​
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/skeleton/2.0.4/skeleton.css" />
  <style>
    body {
      width: 100%;
      margin: 0;
    }
​
    .container {
      margin: 0 auto 6px;
      position: relative;
      width: 960px;
    }
​
    svg {
      position: absolute;
      left: 0;
      top: 0;
    }
​
    .voronoi {
      fill: none;
      stroke: rgba(255, 255, 255, 0.4);
      stroke-width: 4;
    }
​
    .actions-bar {
      opacity: 0.8;
      background-color: white;
      padding: 12px;
      position: absolute;
      top: 0;
      right: 0;
      left: 0;
      z-index: 2;
      text-align: right;
    }
​
    .actions-bar button {
      margin-bottom: 0;
    }
​
    .actions {
      margin: 12px;
    }
​
    .points {
      fill: none;
      stroke: rgba(248, 231, 28, 0.95);
      stroke-width: 3;
    }
  </style>
</head>
​
<body>
  <div class="container">
​
  </div>
  <div class="actions-bar">
    <button onClick='reset()'>Reset</button>
    <button onClick='undo()'>Undo</button>
    <button onClick='togglePoints()'>Toggle Points</button>
  </div>
  <div class="actions row">
    <div class="six columns">
      <label for="exampleEmailInput">Replace image</label>
      <input class="u-full-width" type="url" id="src_url" placeholder="Image URL">
      <button onClick='changeBg()'>Change</button>
    </div>
  </div>
  <script>
    var SRC_IMAGE = "https://gist.githubusercontent.com/samhogg/ddec8105ac38c24b69a120596c9b41d9/raw/74c7e598e84838fa7acda331ceef37554fee5a77/overhead.jpg",
​
      width = 960,
      height = 500,
      pointsOn = false,
      points = [[532, 386], [621, 445], [706, 384], [589, 278], [483, 200], [501, 297], [278, 294], [278, 246], [293, 139], [152, 229], [443, 406], [446, 473], [580, 20], [750, 145], [805, 31]],
​
      canvas = d3.select(".container")
        .append('canvas')
        .attr('width', width)
        .attr('height', height)
        .node(),
​
      context = canvas.getContext("2d"),
      voronoi = d3.voronoi().extent([[0, 0], [width, height]]),
​
      img = new Image();
​
    function draw() {
      context.drawImage(img, 0, 0, width, height);
​
      d3.select('svg').remove();
​
      svg = d3.select('.container')
        .append('svg')
        .attr('width', width)
        .attr('height', height)
        .on('click', svgClick);
​
      // Draw Polygons
      svg.append("g")
        .attr("class", "voronoi")
        .selectAll("path")
        .data(voronoi.polygons(points))
        .enter().append("path")
        .call(drawVoronoi);
​
      // Draw points
      if (pointsOn) {
        svg.append("g")
          .attr("class", "points")
          .selectAll("circle")
          .data(points)
          .enter().append("circle")
          .attr("r", 2.5)
          .call(drawPoint);
      }
    };
​
    function reset() {
      points = [];
      draw();
    };
​
    function undo() {
      points.pop();
      draw();
    };
​
    function togglePoints() {
      pointsOn = !pointsOn;
      draw();
    };
​
    function drawPoint(p) {
      p.attr("cx", function (d) { return d[0]; })
        .attr("cy", function (d) { return d[1]; });
    }
​
    function drawVoronoi(p) {
      p
        .attr("d", function (d) { return d ? "M" + d.join("L") + "Z" : null; });
    }
​
    function svgClick() {
      points.push(d3.mouse(this));
      draw();
    };
​
    function changeBg() {
      var src = document.getElementById('src_url').value
      src.length > 0 ? img.src = src : null;
      points = [];
    };
​
    img.onload = draw;
    img.src = SRC_IMAGE;
  </script>
</body>
    