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Peirce Quincuncial Projection
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<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
padding: 51px 281px;
}
.background {
fill: #a4bac7;
}
.foreground {
fill: none;
stroke: #333;
stroke-width: 1.5px;
}
.graticule {
fill: none;
stroke: #fff;
stroke-width: .5px;
}
.graticule:nth-child(2n) {
stroke-dasharray: 2,2;
}
.land {
fill: #d7c7ad;
stroke: #766951;
}
.boundary {
fill: none;
stroke: #a5967e;
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="https://raw.github.com/d3/d3-plugins/master/geo/projection/projection.js"></script>
<script>
var width = 397,
height = 397,
π = Math.PI;
var front = [90, 0],
back = [270, 0];
function sgn(x) {
return x > 0 ? 1 : x < 0 ? -1 : 0;
}
var guyou = d3.geo.guyou().translate([0, 0]).scale(1);
var projection = d3.geo.projection(function(λ, φ) {
var t = Math.abs(λ) < π / 2,
coordinates = guyou([(t ? λ : -sgn(λ) * (π - Math.abs(λ))) * 180 / π, φ * 180 / π]),
x = coordinates[0] / Math.SQRT2 - coordinates[1] / Math.SQRT2,
y = coordinates[1] / Math.SQRT2 + coordinates[0] / Math.SQRT2;
if (t) return [x, y];
var d = 2 * 1.311028777082283, // TODO unobfuscate
s = (x > 0) ^ (y > 0) ? -1 : 1;
return [s * x - sgn(y) * d, s * y - sgn(x) * d];
})
.scale(75)
.rotate([0, -90, 45])
.translate([width / 2 - .5, height / 2 - .5])
.clipAngle(180 - 1e-6);
var path = d3.geo.path()
.projection(projection);
var center = projection([0, 90]),
w = Math.abs(projection([90, 0])[0] - projection([-90, 0])[0]);
center[0] -= w / 2;
center[1] -= w / 2;
var graticule = d3.geo.graticule()
.step([15, 15]);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height)
.append("g")
.attr("transform", "translate(1.5,1.5)");
svg.append("rect")
.attr("class", "background")
.attr("x", center[0])
.attr("y", center[1])
.attr("width", w)
.attr("height", w);
svg.selectAll(".graticule")
.data(graticule.lines)
.enter().append("path")
.attr("class", "graticule")
.attr("d", path);
svg.append("rect")
.attr("class", "foreground")
.attr("x", center[0])
.attr("y", center[1])
.attr("width", w)
.attr("height", w);
d3.json("readme-boundaries.json", function(err, collection) {
svg.insert("g", ".graticule")
.attr("class", "boundary")
.selectAll("path")
.data(collection.geometries)
.enter().append("path")
.attr("d", path);
});
d3.json("readme-land.json", function(err, collection) {
svg.insert("g", ".graticule,.boundary")
.attr("class", "land")
.selectAll("path")
.data(collection.geometries)
.enter().append("path")
.attr("d", path);
});
</script>
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