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- // https://d3js.org/d3-polygon/ v3.0.1 Copyright 2010-2021 Mike Bostock
- (function (global, factory) {
- typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
- typeof define === 'function' && define.amd ? define(['exports'], factory) :
- (global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.d3 = global.d3 || {}));
- }(this, (function (exports) { 'use strict';
-
- function area(polygon) {
- var i = -1,
- n = polygon.length,
- a,
- b = polygon[n - 1],
- area = 0;
-
- while (++i < n) {
- a = b;
- b = polygon[i];
- area += a[1] * b[0] - a[0] * b[1];
- }
-
- return area / 2;
- }
-
- function centroid(polygon) {
- var i = -1,
- n = polygon.length,
- x = 0,
- y = 0,
- a,
- b = polygon[n - 1],
- c,
- k = 0;
-
- while (++i < n) {
- a = b;
- b = polygon[i];
- k += c = a[0] * b[1] - b[0] * a[1];
- x += (a[0] + b[0]) * c;
- y += (a[1] + b[1]) * c;
- }
-
- return k *= 3, [x / k, y / k];
- }
-
- // Returns the 2D cross product of AB and AC vectors, i.e., the z-component of
- // the 3D cross product in a quadrant I Cartesian coordinate system (+x is
- // right, +y is up). Returns a positive value if ABC is counter-clockwise,
- // negative if clockwise, and zero if the points are collinear.
- function cross(a, b, c) {
- return (b[0] - a[0]) * (c[1] - a[1]) - (b[1] - a[1]) * (c[0] - a[0]);
- }
-
- function lexicographicOrder(a, b) {
- return a[0] - b[0] || a[1] - b[1];
- }
-
- // Computes the upper convex hull per the monotone chain algorithm.
- // Assumes points.length >= 3, is sorted by x, unique in y.
- // Returns an array of indices into points in left-to-right order.
- function computeUpperHullIndexes(points) {
- const n = points.length,
- indexes = [0, 1];
- let size = 2, i;
-
- for (i = 2; i < n; ++i) {
- while (size > 1 && cross(points[indexes[size - 2]], points[indexes[size - 1]], points[i]) <= 0) --size;
- indexes[size++] = i;
- }
-
- return indexes.slice(0, size); // remove popped points
- }
-
- function hull(points) {
- if ((n = points.length) < 3) return null;
-
- var i,
- n,
- sortedPoints = new Array(n),
- flippedPoints = new Array(n);
-
- for (i = 0; i < n; ++i) sortedPoints[i] = [+points[i][0], +points[i][1], i];
- sortedPoints.sort(lexicographicOrder);
- for (i = 0; i < n; ++i) flippedPoints[i] = [sortedPoints[i][0], -sortedPoints[i][1]];
-
- var upperIndexes = computeUpperHullIndexes(sortedPoints),
- lowerIndexes = computeUpperHullIndexes(flippedPoints);
-
- // Construct the hull polygon, removing possible duplicate endpoints.
- var skipLeft = lowerIndexes[0] === upperIndexes[0],
- skipRight = lowerIndexes[lowerIndexes.length - 1] === upperIndexes[upperIndexes.length - 1],
- hull = [];
-
- // Add upper hull in right-to-l order.
- // Then add lower hull in left-to-right order.
- for (i = upperIndexes.length - 1; i >= 0; --i) hull.push(points[sortedPoints[upperIndexes[i]][2]]);
- for (i = +skipLeft; i < lowerIndexes.length - skipRight; ++i) hull.push(points[sortedPoints[lowerIndexes[i]][2]]);
-
- return hull;
- }
-
- function contains(polygon, point) {
- var n = polygon.length,
- p = polygon[n - 1],
- x = point[0], y = point[1],
- x0 = p[0], y0 = p[1],
- x1, y1,
- inside = false;
-
- for (var i = 0; i < n; ++i) {
- p = polygon[i], x1 = p[0], y1 = p[1];
- if (((y1 > y) !== (y0 > y)) && (x < (x0 - x1) * (y - y1) / (y0 - y1) + x1)) inside = !inside;
- x0 = x1, y0 = y1;
- }
-
- return inside;
- }
-
- function length(polygon) {
- var i = -1,
- n = polygon.length,
- b = polygon[n - 1],
- xa,
- ya,
- xb = b[0],
- yb = b[1],
- perimeter = 0;
-
- while (++i < n) {
- xa = xb;
- ya = yb;
- b = polygon[i];
- xb = b[0];
- yb = b[1];
- xa -= xb;
- ya -= yb;
- perimeter += Math.hypot(xa, ya);
- }
-
- return perimeter;
- }
-
- exports.polygonArea = area;
- exports.polygonCentroid = centroid;
- exports.polygonContains = contains;
- exports.polygonHull = hull;
- exports.polygonLength = length;
-
- Object.defineProperty(exports, '__esModule', { value: true });
-
- })));
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