使用turf.js进行面拆分

turfjs是一个地理空间分析库，用于处理各种空间计算

在工作中有需要对图形进行拆分需求，网上也查了一些资料，都不是很好用，所以自己实现了一下，在实现过程中也遇到了点问题。特此分享一下，供大家参考

/*** 拆分多边形* @param feature 待拆分的openlayers feature* @param lineFeature 绘制的分割线段feature* @returns {*[]|*}*/function splitFeature(feature, lineFeature) {let geoJson = new ol.format.GeoJSON();let geojsonFeature = geoJson.writeFeatureObject(feature);//获取由孔生成的featurelet holeFeature = this.getHoleFeature(geojsonFeature);if (geojsonFeature.geometry.type == 'Polygon') {//去掉孔,后面统一处理geojsonFeature.geometry.coordinates = [geojsonFeature.geometry.coordinates[0]]} else {//multipolygon 去掉带孔,后面统一处理geojsonFeature.geometry.coordinates = geojsonFeature.geometry.coordinates.map(c => [c[0]]);}let geojsonSplitFeature = geoJson.writeFeatureObject(lineFeature);let outerLine = turf.polygonToLine(geojsonFeature);outerLine = turf.truncate(outerLine, {precision: 7});let truncatedSplitter = turf.truncate(geojsonSplitFeature, {precision: 7});let intersectCollection = turf.lineIntersect(outerLine, truncatedSplitter);if (intersectCollection.features.length < 2) {return [];}let intersectCombined = turf.combine(intersectCollection).features[0];// split lines with pointslet outerPieceCollection = null;if (outerLine.features) {outerLine.features.forEach(f => {let r = turf.lineSplit(f, intersectCombined);if (!outerPieceCollection) {outerPieceCollection = r;} else {outerPieceCollection.features.push(r);}})} else {//polygonouterPieceCollection = turf.lineSplit(outerLine, intersectCombined);}let splitterPieceCollection = turf.lineSplit(truncatedSplitter, intersectCombined);// polygonize pieceslet pieceCollection = turf.featureCollection(outerPieceCollection.features.concat(splitterPieceCollection.features));let polygonCollection = turf.polygonize(pieceCollection);// 过滤落在外面的feautrelet innerPolygons = this.filterOuterFeatures(feature, polygonCollection.features);// 带孔多边形的处理if (holeFeature) {innerPolygons = innerPolygons.map(p => {return turf.difference(p, holeFeature);})}let innerPolygonCollection = turf.featureCollection(innerPolygons);//转成ol featurelet features = geoJson.readFeatures(innerPolygonCollection);return features;}/*** 获取由geojsonFeature中的孔生成的feature* @param geojsonFeature*/function getHoleFeature(geojsonFeature) {let coordinates;if (geojsonFeature.geometry.type == 'Polygon') {//去掉带孔的,后面统一处理if (geojsonFeature.geometry.coordinates.length > 1) {coordinates = geojsonFeature.geometry.coordinates.slice(1);}} else {coordinates = [];geojsonFeature.geometry.coordinates.forEach(c => {if (c.length > 1) {coordinates = coordinates.concat(c.slice(1));}});}if (!coordinates || coordinates.length == 0) {return null;}return {geometry: {coordinates: coordinates,type: 'MultiPolygon'},type: 'Feature'}}/*** 过滤落在外面的feature* @param orgFeature* @param resultFeatures* @returns {*}*/function filterOuterFeatures(orgFeature, resultFeatures) {let geoJson = new ol.format.GeoJSON();let orgFeatures;if (orgFeature.getGeometry().getType() == 'MultiPolygon') {//multipolygon转多个polygonlet polygons = orgFeature.getGeometry().getPolygons();orgFeatures = polygons.map(polygon => {let feature = new ol.Feature({geometry: polygon});return geoJson.writeFeatureObject(feature);});} else {orgFeatures = [geoJson.writeFeatureObject(orgFeature)];}let innerPolygons = resultFeatures.filter(polygon => {//生成缓冲区let bufferP = turf.buffer(polygon, -0.00000006, {units: 'degrees'});bufferP = turf.truncate(bufferP, {precision: 7});let find = orgFeatures.find(org => {//判断拆分后的面是否落在原始多边形内return turf.booleanContains(org, bufferP);})if (find) {return true;}return false;});return innerPolygons;},

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