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@mbostock
Last active Jul 20, 2019
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Clipped Map Tiles
license: gpl-3.0
redirect: https://observablehq.com/@d3/clipped-map-tiles
d3.geo.tile=function(){function t(){var t=Math.max(Math.log(n)/Math.LN2-8,0),h=Math.round(t+e),o=Math.pow(2,t-h+8),u=[(r[0]-n/2)/o,(r[1]-n/2)/o],l=[],c=d3.range(Math.max(0,Math.floor(-u[0])),Math.max(0,Math.ceil(a[0]/o-u[0]))),M=d3.range(Math.max(0,Math.floor(-u[1])),Math.max(0,Math.ceil(a[1]/o-u[1])));return M.forEach(function(t){c.forEach(function(a){l.push([a,t,h])})}),l.translate=u,l.scale=o,l}var a=[960,500],n=256,r=[a[0]/2,a[1]/2],e=0;return t.size=function(n){return arguments.length?(a=n,t):a},t.scale=function(a){return arguments.length?(n=a,t):n},t.translate=function(a){return arguments.length?(r=a,t):r},t.zoomDelta=function(a){return arguments.length?(e=+a,t):e},t};
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.stroke {
fill: none;
stroke: #000;
stroke-width: .5;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script src="d3.geo.tile.min.js"></script>
<script>
var width = 960,
height = 500;
var projection = d3.geo.mercator()
.center([-96, 38.3])
.scale(890);
var path = d3.geo.path()
.projection(projection);
var tile = d3.geo.tile()
.scale(projection.scale() * 2 * Math.PI)
.translate(projection([0, 0]))
.zoomDelta((window.devicePixelRatio || 1) - .5);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
d3.json("/mbostock/raw/4090846/us.json", function(error, topology) {
if (error) throw error;
var tiles = tile();
var defs = svg.append("defs");
defs.append("path")
.attr("id", "land")
.datum(topojson.feature(topology, topology.objects.land))
.attr("d", path);
defs.append("clipPath")
.attr("id", "clip")
.append("use")
.attr("xlink:href", "#land");
svg.append("g")
.attr("clip-path", "url(#clip)")
.selectAll("image")
.data(tiles)
.enter().append("image")
.attr("xlink:href", function(d) { return "http://" + ["a", "b", "c", "d"][Math.random() * 4 | 0] + ".tiles.mapbox.com/v3/mapbox.natural-earth-2/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
.attr("width", Math.round(tiles.scale))
.attr("height", Math.round(tiles.scale))
.attr("x", function(d) { return Math.round((d[0] + tiles.translate[0]) * tiles.scale); })
.attr("y", function(d) { return Math.round((d[1] + tiles.translate[1]) * tiles.scale); });
svg.append("use")
.attr("xlink:href", "#land")
.attr("class", "stroke");
});
</script>
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