37 lines
1.4 KiB
JavaScript
Executable File
37 lines
1.4 KiB
JavaScript
Executable File
import clone from "@turf/clone";
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import { geometryCollection } from "@turf/helpers";
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import { getType } from "@turf/invariant";
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import { flattenEach } from "@turf/meta";
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import { merge } from "topojson-client";
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import { topology } from "topojson-server";
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/**
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* Dissolves all overlapping (Multi)Polygon
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*
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* @param {FeatureCollection<Polygon|MultiPolygon>} geojson Polygons to dissolve
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* @param {Object} [options={}] Optional parameters
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* @param {boolean} [options.mutate=false] Prevent input mutation
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* @returns {Feature<Polygon|MultiPolygon>} Dissolved Polygons
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*/
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export default function polygonDissolve(geojson, options) {
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if (options === void 0) { options = {}; }
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// Validation
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if (getType(geojson) !== "FeatureCollection") {
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throw new Error("geojson must be a FeatureCollection");
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}
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if (!geojson.features.length) {
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throw new Error("geojson is empty");
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}
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// Clone geojson to avoid side effects
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// Topojson modifies in place, so we need to deep clone first
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if (options.mutate === false || options.mutate === undefined) {
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geojson = clone(geojson);
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}
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var geoms = [];
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flattenEach(geojson, function (feature) {
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geoms.push(feature.geometry);
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});
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var topo = topology({ geoms: geometryCollection(geoms).geometry });
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var merged = merge(topo, topo.objects.geoms.geometries);
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return merged;
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}
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