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@mbostock
Forked from mbostock/.block
Last active Aug 30, 2017
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Canvas Semantic Zooming
license: gpl-3.0
<!DOCTYPE html>
<meta charset="utf-8">
<canvas width="960" height="500"></canvas>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
var canvas = d3.select("canvas").call(d3.zoom().scaleExtent([1, 8]).on("zoom", zoom)),
context = canvas.node().getContext("2d"),
width = canvas.property("width"),
height = canvas.property("height");
var randomX = d3.randomNormal(width / 2, 80),
randomY = d3.randomNormal(height / 2, 80),
data = d3.range(2000).map(function() { return [randomX(), randomY()]; });
draw(d3.zoomIdentity);
function zoom() {
context.clearRect(0, 0, width, height);
draw(d3.event.transform);
}
function draw(transform) {
var i = -1, n = data.length, d;
context.beginPath();
while (++i < n) {
d = transform.apply(data[i]);
context.moveTo(d[0], d[1]);
context.arc(d[0], d[1], 2.5, 0, 2 * Math.PI);
}
context.fill();
}
</script>
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