[unlisted] Tile by Bounding Box (wrap update)

A demo of d3-tile when projecting to fit a bounding box.

Tiles copyright OpenStreetMap contributors.

forked from mbostock's block: Tile by Bounding Box (wrap update)

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

svg,
#tiles {
  position: absolute;
  width: 960px;
  height: 600px;
  overflow: hidden;
}

</style>
<div id="tiles"></div>
<svg width="960" height="600"></svg>
<script src="//d3js.org/d3.v4.0.0-alpha.50.min.js"></script>
<script src="d3-tile.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

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

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

// 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]);

// Compute the projected bounding box given a geographic bounding box (here, California).
// This assumes parallels are horizontal and meridians are vertical…
// but you could use path.bounds to handle arbitrary shapes.
// Note that the y-dimension is flipped relative to latitude!
var bounds = [[-124.408585, 32.534291], [-114.138271, 42.007768]],
    p0 = projection([bounds[0][0], bounds[1][1]]),
    p1 = projection([bounds[1][0], bounds[0][1]]);

// Convert this to a scale k and translate tx, ty for the projection.
// For crisp image tiles, clamp to the nearest power of two.
var k = floor(0.95 / Math.max((p1[0] - p0[0]) / width, (p1[1] - p0[1]) / height)),
    tx = (width - k * (p1[0] + p0[0])) / 2,
    ty = (height - k * (p1[1] + p0[1])) / 2;

projection
    .scale(k / tau)
    .translate([tx, ty]);

// Lastly convert this to the corresponding tile.scale and tile.translate;
// see https://bl.ocks.org/mbostock/4150951 for a related example.
var tiles = d3.tile()
    .size([width, height])
    .scale(k)
    .translate([tx, ty])
    ();

d3.select("#tiles")
  .selectAll("img").data(tiles).enter().append("img")
    .style("position", "absolute")
    .attr("src", function(d, i) { return "https://" + "abc"[d[1] % 3] + ".tile.openstreetmap.org/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
    .style("left", function(d) { return (d.x / tiles.scale + tiles.translate[0]) * tiles.scale + "px"; })
    .style("top", function(d) { return (d.y / tiles.scale + tiles.translate[1]) * tiles.scale + "px"; })
    .attr("width", tiles.scale)
    .attr("height", tiles.scale);

d3.json("https://gist.githubusercontent.com/mbostock/4090846/raw/d534aba169207548a8a3d670c9c2cc719ff05c47/us.json", function(error, us) {
  if (error) throw error;

svg.append("path")
      .datum(topojson.mesh(us, us.objects.states))
      .attr("d", d3.geoPath().projection(projection))
      .attr("fill", "none")
      .attr("stroke", "#000");
});

function floor(k) {
  return Math.pow(2, Math.floor(Math.log(k) / Math.LN2));
}

</script>

https://d3js.org/d3.v4.0.0-alpha.50.min.js

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