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Map Pan & Zoom III
license: gpl-3.0
.DS_Store
build
node_modules

This example uses d3.behavior.zoom with a canvas transform and pre-projected geometry for map panning and zooming. This approach is faster than reprojecting, but still slower than an SVG transform. A faster variation of this approach is to use dynamic simplification and viewport clipping.

<!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 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";
context.strokeStyle = "#fff";
var path = d3.geo.path()
.projection(null)
.context(context);
d3.json("world.json", function(error, world) {
if (error) throw error;
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() {
var t = zoom.translate(),
s = zoom.scale();
context.clearRect(0, 0, width, height);
context.save();
context.translate(t[0], t[1]);
context.scale(s, s);
context.lineWidth = 1 / s;
context.beginPath();
path(sphere);
context.fillStyle = "#fff";
context.fill();
context.beginPath();
path(land);
context.fillStyle = "#000";
context.fill();
context.beginPath();
path(boundary);
context.stroke();
context.restore();
}
});
d3.select(self.frameElement).style("height", height + "px");
</script>
GENERATED_FILES = \
world.json
all: $(GENERATED_FILES)
clean:
rm -rf -- %(GENERATED_FILES)
.PHONY: all clean
build/ne_50m_admin_0_countries.zip:
mkdir -p $(dir $@)
curl -o $@ 'http://www.nacis.org/naturalearth/50m/cultural/$(notdir $@)'
build/ne_50m_admin_0_countries.shp: build/ne_50m_admin_0_countries.zip
unzip -d $(dir $@) $<
touch $@
world.json: build/ne_50m_admin_0_countries.shp sphere.json
node_modules/.bin/topojson \
-q 1e5 \
--projection='width = 960, height = 960, d3.geo.mercator() \
.translate([width / 2, height / 2]) \
.scale((width - 1) / 2 / Math.PI)' \
-- \
countries=build/ne_50m_admin_0_countries.shp \
sphere=sphere.json | \
node_modules/.bin/topojson-merge \
-o $@ \
--io=countries \
--oo=land
{
"name": "anonymous",
"version": "0.0.1",
"private": true,
"dependencies": {
"topojson": "1"
}
}
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@Stonelinks
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Quick question: what is that sphere.json Makefile target? I'm trying to adapt this to work with the 10m map and it seems to be missing.

Also the URL for the naturalearth data is 404ing. Looks like this works though: http://naciscdn.org/naturalearth/50m/cultural/ne_50m_admin_0_countries.zip

Thanks!

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