84 lines
3.1 KiB
JavaScript
Executable File
84 lines
3.1 KiB
JavaScript
Executable File
import distance from "@turf/distance";
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import { feature, featureCollection } from "@turf/helpers";
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import { featureEach } from "@turf/meta";
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import tin from "@turf/tin";
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import dissolve from "./lib/turf-dissolve.js";
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/**
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* Takes a set of {@link Point|points} and returns a concave hull Polygon or MultiPolygon.
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* Internally, this uses [turf-tin](https://github.com/Turfjs/turf-tin) to generate geometries.
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*
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* @name concave
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* @param {FeatureCollection<Point>} points input points
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* @param {Object} [options={}] Optional parameters
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* @param {number} [options.maxEdge=Infinity] the length (in 'units') of an edge necessary for part of the
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* hull to become concave.
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* @param {string} [options.units='kilometers'] can be degrees, radians, miles, or kilometers
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* @returns {Feature<(Polygon|MultiPolygon)>|null} a concave hull (null value is returned if unable to compute hull)
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* @example
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* var points = turf.featureCollection([
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* turf.point([-63.601226, 44.642643]),
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* turf.point([-63.591442, 44.651436]),
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* turf.point([-63.580799, 44.648749]),
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* turf.point([-63.573589, 44.641788]),
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* turf.point([-63.587665, 44.64533]),
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* turf.point([-63.595218, 44.64765])
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* ]);
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* var options = {units: 'miles', maxEdge: 1};
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*
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* var hull = turf.concave(points, options);
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*
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* //addToMap
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* var addToMap = [points, hull]
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*/
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function concave(points, options) {
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if (options === void 0) { options = {}; }
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var maxEdge = options.maxEdge || Infinity;
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var cleaned = removeDuplicates(points);
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var tinPolys = tin(cleaned);
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// calculate length of all edges and area of all triangles
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// and remove triangles that fail the max length test
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tinPolys.features = tinPolys.features.filter(function (triangle) {
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var pt1 = triangle.geometry.coordinates[0][0];
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var pt2 = triangle.geometry.coordinates[0][1];
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var pt3 = triangle.geometry.coordinates[0][2];
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var dist1 = distance(pt1, pt2, options);
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var dist2 = distance(pt2, pt3, options);
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var dist3 = distance(pt1, pt3, options);
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return dist1 <= maxEdge && dist2 <= maxEdge && dist3 <= maxEdge;
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});
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if (tinPolys.features.length < 1) {
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return null;
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}
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// merge the adjacent triangles
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var dissolved = dissolve(tinPolys);
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// geojson-dissolve always returns a MultiPolygon
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if (dissolved.coordinates.length === 1) {
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dissolved.coordinates = dissolved.coordinates[0];
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dissolved.type = "Polygon";
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}
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return feature(dissolved);
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}
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/**
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* Removes duplicated points in a collection returning a new collection
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*
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* @private
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* @param {FeatureCollection<Point>} points to be cleaned
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* @returns {FeatureCollection<Point>} cleaned set of points
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*/
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function removeDuplicates(points) {
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var cleaned = [];
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var existing = {};
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featureEach(points, function (pt) {
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if (!pt.geometry) {
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return;
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}
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var key = pt.geometry.coordinates.join("-");
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if (!Object.prototype.hasOwnProperty.call(existing, key)) {
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cleaned.push(pt);
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existing[key] = true;
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}
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});
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return featureCollection(cleaned);
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}
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export default concave;
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