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87 lines
2.4 KiB
TypeScript
87 lines
2.4 KiB
TypeScript
import { pointsEqual } from "./point";
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import { segment, segmentIncludesPoint, segmentsIntersectAt } from "./segment";
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import type { GenericPoint, Polygon, Segment } from "./types";
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import { PRECISION } from "./utils";
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export function polygon<Point extends GenericPoint>(...points: Point[]) {
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return polygonClose(points) as Polygon<Point>;
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}
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export function polygonFromPoints<Point extends GenericPoint>(points: Point[]) {
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return polygonClose(points) as Polygon<Point>;
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}
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export const polygonIncludesPoint = <Point extends GenericPoint>(
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point: Point,
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polygon: Polygon<Point>,
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) => {
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const x = point[0];
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const y = point[1];
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let inside = false;
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for (let i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
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const xi = polygon[i][0];
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const yi = polygon[i][1];
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const xj = polygon[j][0];
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const yj = polygon[j][1];
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if (
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((yi > y && yj <= y) || (yi <= y && yj > y)) &&
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x < ((xj - xi) * (y - yi)) / (yj - yi) + xi
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) {
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inside = !inside;
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}
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}
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return inside;
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};
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export const pointOnPolygon = <Point extends GenericPoint>(
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p: Point,
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poly: Polygon<Point>,
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threshold = PRECISION,
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) => {
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let on = false;
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for (let i = 0, l = poly.length - 1; i < l; i++) {
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if (segmentIncludesPoint(p, segment(poly[i], poly[i + 1]), threshold)) {
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on = true;
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break;
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}
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}
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return on;
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};
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function polygonClose<Point extends GenericPoint>(polygon: Point[]) {
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return polygonIsClosed(polygon)
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? polygon
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: ([...polygon, polygon[0]] as Polygon<Point>);
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}
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function polygonIsClosed<Point extends GenericPoint>(polygon: Point[]) {
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return pointsEqual(polygon[0], polygon[polygon.length - 1]);
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}
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/**
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* Returns the points of intersection of a line segment, identified by exactly
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* one start pointand one end point, and the polygon identified by a set of
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* ponits representing a set of connected lines.
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*/
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export function polygonSegmentIntersectionPoints<Point extends GenericPoint>(
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polygon: Readonly<Polygon<Point>>,
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segment: Readonly<Segment<Point>>,
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): Point[] {
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return polygon
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.reduce((segments, current, idx, poly) => {
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return idx === 0
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? []
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: ([
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...segments,
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[poly[idx - 1] as Point, current],
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] as Segment<Point>[]);
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}, [] as Segment<Point>[])
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.map((s) => segmentsIntersectAt(s, segment))
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.filter((point) => point !== null) as Point[];
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}
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