Duotone map tiles w/ an SVG transform by wboykinm

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  margin: 0;
}

path {
  fill: none;
  stroke: red;
  stroke-linejoin: round;
  stroke-width: 1.5px;
}

</style>
<svg>
  <defs>
    <filter id="duotone" color-interpolation-filters="sRGB">
      <feColorMatrix type="saturate" values="0" />
      <feColorMatrix type="matrix" />
    </filter>
  </defs>
</svg>
<script src="//d3js.org/d3.v4.0.0-rc.1.min.js"></script>
<script src="//d3js.org/d3-tile.v0.0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var pi = Math.PI,
    tau = 2 * pi;

var width = Math.max(960, window.innerWidth),
    height = Math.max(500, window.innerHeight);

// Initialize the projection to fit the world in a 1×1 square centered at the origin.
var projection = d3.geoMercator()
    .scale(1 / tau)
    .translate([0, 0]);

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

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

var zoom = d3.zoom()
    .scaleExtent([1 << 11, 1 << 14])
    .on("zoom", zoomed);

var svg = d3.select("svg")
    .attr("width", width)
    .attr("height", height);

var raster = svg.append("g");

// Compute the projected initial center.
var center = projection([-77.03687,38.8919]);

// Apply a zoom transform equivalent to projection.{scale,translate,center}.
svg
  .call(zoom)
  .call(zoom.transform, d3.zoomIdentity
      .translate(width / 2, height / 2)
      .scale(1 << 22)
      .translate(-center[0], -center[1]));

function zoomed() {
  var transform = d3.event.transform;

  var tiles = tile
      .scale(transform.k)
      .translate([transform.x, transform.y])
      ();

  projection
      .scale(transform.k / tau)
      .translate([transform.x, transform.y]);

  var image = raster
      .attr("transform", stringify(tiles.scale, tiles.translate))
    .selectAll("image")
    .data(tiles, function(d) { return d; });

  image.exit().remove();

  image.enter().append("image")
      .attr("xlink:href", function(d) { return "//" + "abc"[d[1] % 3] + ".tile.stamen.com/toner/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
      .attr("x", function(d) { return d[0] * 256; })
      .attr("y", function(d) { return d[1] * 256; })
      .attr("width", 256)
      .attr("height", 256)
      .attr("filter","url(#duotone)");
}

function type(d) {
  return {
    type: "Feature",
    properties: {name: d.description, state: d.name},
    geometry: {type: "Point", coordinates: [+d.longitude, +d.latitude]}
  };
}

function stringify(scale, translate) {
  var k = scale / 256, r = scale % 1 ? Number : Math.round;
  return "translate(" + r(translate[0] * scale) + "," + r(translate[1] * scale) + ") scale(" + k + ")";
}

var filter = d3.select("feColorMatrix:last-child"),
      matrix = [
        [ 0,  0,  0,  0,  0 ],
        [ 0,  0,  0,  0,  0 ],
        [ 0,  0,  0,  0,  0 ],
        [ 0,  0,  0,  1,  0 ],
      ];

  d3.timer(function(t){

    var bg,
        fg;

    t = t % 7500 / 7500;
    if (t > 0.5) t = 1 - t;

    fg = d3.rgb(d3.interpolateWarm(t)).darker(0.75);
    bg = d3.rgb(d3.interpolateCool(1 - t)).brighter(0.1);

    ["r", "g", "b"].forEach(function(d, i){
      matrix[i][i] = (bg[d] - fg[d]) / 256;
      matrix[i][4] = fg[d] / 256;
    });

    filter.attr("values", matrix.join(" "));

  });
  
</script>