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<!DOCTYPE html>
<style>
    img.tile {
        position:absolute;
    }
    #download {
        position:absolute;
        top:10px;
        left:10px;
    }
</style>
<body>
    <canvas id='map'></canvas>
    <button id='download'>download</button>
    <div style='display:none;' id='loader'></div>
<script src="https://d3js.org/d3.v2.js"></script>
<script>
  var width = 960,
      height = 500,
      projection = d3.geo.mercator().scale(1024).translate([512, 256]),
      path = d3.geo.path().projection(projection);

var container = d3.select("#map")
      .attr("width", width)
      .attr("height", height)
      .call(d3.behavior.zoom()
        .translate(projection.translate())
        .scale(projection.scale())
        .on("zoom", redraw));

function tileUrl(d) {
      return 'https://a.tiles.mapbox.com/v3/landplanner.map-t9b87ncx/' + d[0] + '/' + d[1] + '/' + d[2] + '.png';
  }
  var canvas = d3.select('#map').node();
  var ctx = canvas.getContext('2d');
  d3.select('#download').on('click', function() {
      window.open(canvas.toDataURL(), "image", "width=960, height=500");
  });

function redraw() {
    if (d3.event && d3.event.translate) {
      projection
          .translate(d3.event.translate)
          .scale(d3.event.scale);
    }

var t = projection.translate(),
        s = projection.scale(),
        z = Math.max(Math.log(s) / Math.log(2) - 8, 0);
        rz = Math.floor(z),
        ts = 256 * Math.pow(2, z - rz);

// This is the 0, 0 px of the projection
    var tile_origin = [s / 2 - t[0], s / 2 - t[1]];

var cols = d3.range(Math.max(0, Math.floor(tile_origin[0] / ts)),
        Math.max(0, Math.ceil((tile_origin[0] + width) / ts)));

var rows = d3.range(Math.max(0, Math.floor(tile_origin[1] / ts)),
        Math.max(0, Math.ceil((tile_origin[1] + height) / ts)));

var coords = [];

cols.forEach(function(x) {
        rows.forEach(function(y) {
            coords.push([Math.floor(z), x, y, [Math.floor(z), x, y].join(',')]);
        });
    });

canvas.width = canvas.width;

var tiles = d3.select('#loader').selectAll('img.tile')
        .data(coords, function(d) { return d[3]; });

tiles.enter().append('img')
        .property('crossOrigin', '*')
        .attr('class', 'tile')
        .attr('src', tileUrl)
        .on('load', function(d) {
            redraw();
        });

tiles.each(function(d) {
        if (!this.naturalWidth) return;
        ctx.drawImage(this,
            ((d[1] * ts) - tile_origin[0]), ((d[2] * ts) - tile_origin[1]),
            ts, ts);
    });
}

redraw();
</script>

Modified http://d3js.org/d3.v2.js to a secure url

https://d3js.org/d3.v2.js