Andrew’s monotone chain algorithm computes the convex hull of a set of two-dimensional points.
Convex Hull
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license: gpl-3.0 |
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<!DOCTYPE html> | |
<meta charset="utf-8"> | |
<canvas width="960" height="500"></canvas> | |
<script src="//d3js.org/d3-random.v0.1.min.js"></script> | |
<script src="//d3js.org/d3-polygon.v0.1.min.js"></script> | |
<script> | |
var canvas = document.querySelector("canvas"), | |
context = canvas.getContext("2d"); | |
var width = canvas.width, | |
height = canvas.height; | |
var randomX = d3_random.normal(width / 2, 60), | |
randomY = d3_random.normal(height / 2, 60), | |
points = new Array(100); | |
for (var i = 0, n = points.length; i < n; ++i) points[i] = [randomX(), randomY()]; | |
render(); | |
window.addEventListener("mousemove", function(event) { | |
var rect = canvas.getBoundingClientRect(), | |
x = event.clientX - rect.left - canvas.clientLeft, | |
y = event.clientY - rect.top - canvas.clientTop; | |
points[0][0] = x; | |
points[0][1] = y; | |
render(); | |
}); | |
function render() { | |
context.clearRect(0, 0, width, height); | |
var hull = d3_polygon.hull(points); | |
context.beginPath(); | |
context.moveTo(hull[0][0], hull[0][1]); | |
for (var i = 1, n = hull.length; i < n; ++i) { | |
context.lineTo(hull[i][0], hull[i][1]); | |
} | |
context.closePath(); | |
context.fillStyle = "steelblue"; | |
context.fill(); | |
context.lineWidth = 15; | |
context.lineJoin = "round"; | |
context.strokeStyle = "steelblue"; | |
context.stroke(); | |
context.beginPath(); | |
for (var i = 0, n = points.length; i < n; ++i) { | |
context.moveTo(points[i][0] + 2.5, points[i][1]); | |
context.arc(points[i][0], points[i][1], 2.5, 0, 2 * Math.PI); | |
} | |
context.fillStyle = "white"; | |
context.fill(); | |
context.lineWidth = 1.5; | |
context.strokeStyle = "black"; | |
context.stroke(); | |
} | |
</script> |
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