82 lines
2.6 KiB
JavaScript
Executable File
82 lines
2.6 KiB
JavaScript
Executable File
import { isObject, multiPolygon, featureCollection } from '@turf/helpers';
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import { collectionOf } from '@turf/invariant';
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import { featureEach } from '@turf/meta';
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import flatten from '@turf/flatten';
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import polygonClipping from 'polygon-clipping';
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/**
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* Dissolves a FeatureCollection of {@link polygon} features, filtered by an optional property name:value.
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* Note that {@link mulitpolygon} features within the collection are not supported
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*
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* @name dissolve
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* @param {FeatureCollection<Polygon>} featureCollection input feature collection to be dissolved
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* @param {Object} [options={}] Optional parameters
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* @param {string} [options.propertyName] features with the same `propertyName` value will be dissolved.
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* @returns {FeatureCollection<Polygon>} a FeatureCollection containing the dissolved polygons
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* @example
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* var features = turf.featureCollection([
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* turf.polygon([[[0, 0], [0, 1], [1, 1], [1, 0], [0, 0]]], {combine: 'yes'}),
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* turf.polygon([[[0, -1], [0, 0], [1, 0], [1, -1], [0,-1]]], {combine: 'yes'}),
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* turf.polygon([[[1,-1],[1, 0], [2, 0], [2, -1], [1, -1]]], {combine: 'no'}),
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* ]);
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*
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* var dissolved = turf.dissolve(features, {propertyName: 'combine'});
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*
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* //addToMap
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* var addToMap = [features, dissolved]
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*/
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function dissolve(fc, options) {
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// Optional parameters
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options = options || {};
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if (!isObject(options)) throw new Error("options is invalid");
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var propertyName = options.propertyName;
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// Input validation
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collectionOf(fc, "Polygon", "dissolve");
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// Main
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var outFeatures = [];
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if (!options.propertyName) {
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return flatten(
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multiPolygon(
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polygonClipping.union.apply(
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null,
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fc.features.map(function (f) {
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return f.geometry.coordinates;
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})
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)
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)
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);
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} else {
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var uniquePropertyVals = {};
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featureEach(fc, function (feature) {
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if (
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!Object.prototype.hasOwnProperty.call(
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uniquePropertyVals,
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feature.properties[propertyName]
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)
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) {
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uniquePropertyVals[feature.properties[propertyName]] = [];
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}
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uniquePropertyVals[feature.properties[propertyName]].push(feature);
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});
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var vals = Object.keys(uniquePropertyVals);
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for (var i = 0; i < vals.length; i++) {
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var mp = multiPolygon(
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polygonClipping.union.apply(
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null,
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uniquePropertyVals[vals[i]].map(function (f) {
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return f.geometry.coordinates;
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})
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)
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);
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mp.properties[propertyName] = vals[i];
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outFeatures.push(mp);
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}
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}
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return flatten(featureCollection(outFeatures));
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}
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export default dissolve;
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