Equirectangular Fisheye by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 480;

var projection = equirectangularFisheye()
    .scale(153)
    .translate([width / 2, height / 2])
    .precision(0);

var canvas = d3.select("body").append("canvas")
    .attr("width", width)
    .attr("height", height);

var context = canvas.node().getContext("2d");

context.lineWidth = .5;

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

d3.json("/mbostock/raw/4090846/world-110m.json", function(error, world) {
  if (error) throw error;

  var graticule = d3.geo.graticule()(),
      land = topojson.feature(world, world.objects.land),
      boundary = topojson.mesh(world, world.objects.countries, function(a, b) { return a !== b; });

  canvas
      .on("ontouchmove" in window ? "touchmove" : "mousemove", moved);

  render();

  function moved() {
    var m = d3.mouse(this);

    // After changing the focus, ensure the focus is centered at the mouse.
    projection
        .focus([(m[0] / width - .5) * 360, (.5 - m[1] / height) * 180])
        .center(projection.focus())
        .translate(m);

    render();

    d3.event.preventDefault();
  }

  function render() {
    context.clearRect(0, 0, width, height);

    context.beginPath();
    path(land);
    context.globalAlpha = 1;
    context.fillStyle = "#222";
    context.fill();

    context.beginPath();
    path(boundary);
    context.strokeStyle = "#fff";
    context.stroke();

    context.beginPath();
    path(graticule);
    context.globalAlpha = .5;
    context.strokeStyle = "#777";
    context.stroke();
  }
});

d3.select(self.frameElement).style("height", height + "px");

function equirectangularFisheye() {
  var distortion = 3,
      focus = [0, 0],
      π = Math.PI,
      m = d3.geo.projectionMutator(raw),
      p = m(distortion, focus);

  function raw(distortion, focus) {
    var fx = fisheye(distortion, focus[0], -π, +π),
        fy = fisheye(distortion, focus[1], -π / 2, +π / 2);
    return function(x, y) {
      return [fx(x), fy(y)];
    };
  }

  p.distortion = function(_) {
    return arguments.length
        ? m(distortion = +_, focus)
        : distortion;
  };

  p.focus = function(_) {
    return arguments.length
        ? m(distortion, focus = [_[0] * π / 180, _[1] * π / 180])
        : [focus[0] * 180 / π, focus[1] * 180 / π];
  };

  return p;
}

function fisheye(distortion, focus, min, max) {
  return function(x) {
    var offset = (x < focus ? focus - min : max - focus) || (max - min);
    return (x < focus ? -1 : +1) * offset * (distortion + 1) / (distortion + (offset / Math.abs(x - focus))) + focus;
  };
}

</script>