150 lines
4.3 KiB
JavaScript
Executable File
150 lines
4.3 KiB
JavaScript
Executable File
import explode from '@turf/explode';
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import centroid from '@turf/center';
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import nearestPoint from '@turf/nearest-point';
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import booleanPointInPolygon from '@turf/boolean-point-in-polygon';
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import { featureCollection, point, feature } from '@turf/helpers';
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/**
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* Takes a Feature or FeatureCollection and returns a {@link Point} guaranteed to be on the surface of the feature.
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*
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* * Given a {@link Polygon}, the point will be in the area of the polygon
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* * Given a {@link LineString}, the point will be along the string
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* * Given a {@link Point}, the point will the same as the input
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*
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* @name pointOnFeature
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* @param {GeoJSON} geojson any Feature or FeatureCollection
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* @returns {Feature<Point>} a point on the surface of `input`
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* @example
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* var polygon = turf.polygon([[
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* [116, -36],
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* [131, -32],
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* [146, -43],
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* [155, -25],
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* [133, -9],
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* [111, -22],
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* [116, -36]
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* ]]);
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*
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* var pointOnPolygon = turf.pointOnFeature(polygon);
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*
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* //addToMap
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* var addToMap = [polygon, pointOnPolygon];
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*/
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function pointOnFeature(geojson) {
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// normalize
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var fc = normalize(geojson);
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// get centroid
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var cent = centroid(fc);
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// check to see if centroid is on surface
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var onSurface = false;
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var i = 0;
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while (!onSurface && i < fc.features.length) {
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var geom = fc.features[i].geometry;
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var x, y, x1, y1, x2, y2, k;
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var onLine = false;
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if (geom.type === "Point") {
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if (
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cent.geometry.coordinates[0] === geom.coordinates[0] &&
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cent.geometry.coordinates[1] === geom.coordinates[1]
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) {
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onSurface = true;
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}
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} else if (geom.type === "MultiPoint") {
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var onMultiPoint = false;
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k = 0;
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while (!onMultiPoint && k < geom.coordinates.length) {
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if (
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cent.geometry.coordinates[0] === geom.coordinates[k][0] &&
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cent.geometry.coordinates[1] === geom.coordinates[k][1]
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) {
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onSurface = true;
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onMultiPoint = true;
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}
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k++;
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}
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} else if (geom.type === "LineString") {
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k = 0;
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while (!onLine && k < geom.coordinates.length - 1) {
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x = cent.geometry.coordinates[0];
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y = cent.geometry.coordinates[1];
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x1 = geom.coordinates[k][0];
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y1 = geom.coordinates[k][1];
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x2 = geom.coordinates[k + 1][0];
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y2 = geom.coordinates[k + 1][1];
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if (pointOnSegment(x, y, x1, y1, x2, y2)) {
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onLine = true;
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onSurface = true;
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}
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k++;
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}
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} else if (geom.type === "MultiLineString") {
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var j = 0;
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while (j < geom.coordinates.length) {
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onLine = false;
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k = 0;
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var line = geom.coordinates[j];
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while (!onLine && k < line.length - 1) {
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x = cent.geometry.coordinates[0];
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y = cent.geometry.coordinates[1];
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x1 = line[k][0];
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y1 = line[k][1];
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x2 = line[k + 1][0];
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y2 = line[k + 1][1];
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if (pointOnSegment(x, y, x1, y1, x2, y2)) {
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onLine = true;
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onSurface = true;
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}
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k++;
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}
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j++;
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}
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} else if (geom.type === "Polygon" || geom.type === "MultiPolygon") {
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if (booleanPointInPolygon(cent, geom)) {
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onSurface = true;
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}
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}
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i++;
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}
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if (onSurface) {
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return cent;
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} else {
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var vertices = featureCollection([]);
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for (i = 0; i < fc.features.length; i++) {
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vertices.features = vertices.features.concat(
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explode(fc.features[i]).features
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);
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}
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// Remove distanceToPoint properties from nearestPoint()
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return point(nearestPoint(cent, vertices).geometry.coordinates);
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}
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}
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/**
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* Normalizes any GeoJSON to a FeatureCollection
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*
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* @private
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* @name normalize
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* @param {GeoJSON} geojson Any GeoJSON
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* @returns {FeatureCollection} FeatureCollection
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*/
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function normalize(geojson) {
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if (geojson.type !== "FeatureCollection") {
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if (geojson.type !== "Feature") {
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return featureCollection([feature(geojson)]);
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}
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return featureCollection([geojson]);
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}
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return geojson;
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}
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function pointOnSegment(x, y, x1, y1, x2, y2) {
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var ab = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
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var ap = Math.sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
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var pb = Math.sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y));
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return ab === ap + pb;
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}
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export default pointOnFeature;
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