Map Pan & Zoom IV

This example uses d3.behavior.zoom with pre-projected geometry for map panning and zooming, in conjunction with dynamic simplification and viewport clipping. This approach is quite fast, but more work to implement than an SVG transform.

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

canvas {
  background: #eee;
}

</style>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<body>
<script>

var width = 960,
    height = 960;

var scale,
    translate,
    area; // minimum area threshold for simplification

var clip = d3.geo.clipExtent()
    .extent([[0, 0], [width, height]]);

var simplify = d3.geo.transform({
  point: function(x, y, z) {
    if (z >= area) this.stream.point(x * scale + translate[0], y * scale + translate[1]);
  }
});

var zoom = d3.behavior.zoom()
    .translate([0, 0])
    .scale(1)
    .scaleExtent([1, 8]);

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

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

context.lineJoin = "round";
context.lineCap = "round";

var path = d3.geo.path()
    .projection({stream: function(s) { return simplify.stream(clip.stream(s)); }})
    .context(context);

d3.json("world.json", function(error, world) {
  if (error) throw error;

topojson.presimplify(world);

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

canvas
      .call(zoom.on("zoom", zoomed))
      .call(zoom.event);

function zoomed() {
    translate = zoom.translate();
    scale = zoom.scale();
    area = 1 / scale / scale;

context.clearRect(0, 0, width, height);

context.save();

context.beginPath();
    path(sphere);
    context.fillStyle = "#fff";
    context.fill();

context.beginPath();
    path(land);
    context.fillStyle = "#000";
    context.fill();

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

context.restore();
  }
});

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

</script>

https://d3js.org/d3.v3.min.js

https://d3js.org/topojson.v1.min.js