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Copy pathpolygon.js
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105 lines (90 loc) · 2.42 KB
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import "../core/subclass";
import "geom";
d3.geom.polygon = function(coordinates) {
d3_subclass(coordinates, d3_geom_polygonPrototype);
return coordinates;
};
var d3_geom_polygonPrototype = d3.geom.polygon.prototype = [];
d3_geom_polygonPrototype.area = function() {
var i = -1,
n = this.length,
a,
b = this[n - 1],
area = 0;
while (++i < n) {
a = b;
b = this[i];
area += a[1] * b[0] - a[0] * b[1];
}
return area * .5;
};
d3_geom_polygonPrototype.centroid = function(k) {
var i = -1,
n = this.length,
x = 0,
y = 0,
a,
b = this[n - 1],
c;
if (!arguments.length) k = -1 / (6 * this.area());
while (++i < n) {
a = b;
b = this[i];
c = a[0] * b[1] - b[0] * a[1];
x += (a[0] + b[0]) * c;
y += (a[1] + b[1]) * c;
}
return [x * k, y * k];
};
// The Sutherland-Hodgman clipping algorithm.
// Note: requires the clip polygon to be counterclockwise and convex.
d3_geom_polygonPrototype.clip = function(subject) {
var input,
closed = d3_geom_polygonClosed(subject),
i = -1,
n = this.length - d3_geom_polygonClosed(this),
j,
m,
a = this[n - 1],
b,
c,
d;
while (++i < n) {
input = subject.slice();
subject.length = 0;
b = this[i];
c = input[(m = input.length - closed) - 1];
j = -1;
while (++j < m) {
d = input[j];
if (d3_geom_polygonInside(d, a, b)) {
if (!d3_geom_polygonInside(c, a, b)) {
subject.push(d3_geom_polygonIntersect(c, d, a, b));
}
subject.push(d);
} else if (d3_geom_polygonInside(c, a, b)) {
subject.push(d3_geom_polygonIntersect(c, d, a, b));
}
c = d;
}
if (closed) subject.push(subject[0]);
a = b;
}
return subject;
};
function d3_geom_polygonInside(p, a, b) {
return (b[0] - a[0]) * (p[1] - a[1]) < (b[1] - a[1]) * (p[0] - a[0]);
}
// Intersect two infinite lines cd and ab.
function d3_geom_polygonIntersect(c, d, a, b) {
var x1 = c[0], x3 = a[0], x21 = d[0] - x1, x43 = b[0] - x3,
y1 = c[1], y3 = a[1], y21 = d[1] - y1, y43 = b[1] - y3,
ua = (x43 * (y1 - y3) - y43 * (x1 - x3)) / (y43 * x21 - x43 * y21);
return [x1 + ua * x21, y1 + ua * y21];
}
// Returns true if the polygon is closed.
function d3_geom_polygonClosed(coordinates) {
var a = coordinates[0],
b = coordinates[coordinates.length - 1];
return !(a[0] - b[0] || a[1] - b[1]);
}