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Last active December 21, 2015 18:19
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Map Zooming (Doin’ It Right)

For best viewing experience, please play “Doin’ It Right (feat. Panda Bear)” off the latest Daft Punk album while watching this animation.

<iframe width="560" height="315" src="//www.youtube.com/embed/RA5PRj7KPkE" frameborder="0" allowfullscreen></iframe>
<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="http://d3js.org/topojson.v1.min.js"></script>
<script>
var width = 960,
height = 500;
var sf = [-122.417, 37.775],
ny = [-74.0064, 40.7142];
var scale,
translate,
visibleArea, // minimum area threshold for points inside viewport
invisibleArea; // minimum area threshold for points outside viewport
var simplify = d3.geo.transform({
point: function(x, y, z) {
if (z < visibleArea) return;
x = x * scale + translate[0];
y = y * scale + translate[1];
if (x >= -10 && x <= width + 10 && y >= -10 && y <= height + 10 || z >= invisibleArea) this.stream.point(x, y);
}
});
var zoom = d3.behavior.zoom()
.size([width, height])
.on("zoom", zoomed);
// This projection is baked into the TopoJSON file,
// but is used here to compute the desired zoom translate.
var projection = d3.geo.mercator()
.translate([0, 0])
.scale(4000);
var canvas = d3.select("body").append("canvas")
.attr("width", width)
.attr("height", height);
var context = canvas.node().getContext("2d");
var path = d3.geo.path()
.projection(simplify)
.context(context);
d3.json("us-states.json", function(error, json) {
canvas
.datum(topojson.mesh(topojson.presimplify(json)))
.call(zoomTo(sf, 4).event)
.transition()
.duration(60 * 1000 / 89 * 2)
.each(jump);
});
function zoomTo(location, scale) {
var point = projection(location);
return zoom
.translate([width / 2 - point[0] * scale, height / 2 - point[1] * scale])
.scale(scale);
}
function zoomed(d) {
translate = zoom.translate();
scale = zoom.scale();
visibleArea = 1 / scale / scale;
invisibleArea = 200 * visibleArea;
context.clearRect(0, 0, width, height);
context.beginPath();
path(d);
context.stroke();
}
function jump() {
var t = d3.select(this);
(function repeat() {
t = t.transition()
.call(zoomTo(ny, 6).event)
.transition()
.call(zoomTo(sf, 4).event)
.each("end", repeat);
})();
}
</script>
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