OpenLayers6（8）：引入Turf.js做缓冲区分析_openlayers turf geojson 相交分析

1 版本

• OpenLayers：6.14.1

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2 相关配置

//前端的地理空间分析库，处理各种地图算法
 
npm i @turf/turf

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3 Openlayers图形与图形Turf之间的互相转换

使用策略模式进行实现：

/**
 * 策略模式，不同类型返回不同的Turf几何图形
 */
export const mCoords2TurfGeom = {
    Point: function (coords) {
        return turf.point(coords);
    },
    MultiPoint: function (coords) {
        return turf.multiPoint(coords);
    },
    LineString: function (coords) {
        return turf.lineString(coords);
    },
    MultiLineString: function (coords) {
        return turf.multiLineString(coords);
    },
    Polygon: function (coords) {
        return turf.polygon(coords);
    },
    MultiPolygon: function (coords) {
        return turf.multiPolygon(coords);
    },
}

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4 openlayers的要素点击事件

基于地图的"singleclick"点击事件拾取要素：

/**
 * 选择要素
 * @param {*} map 地图对象
 * @param {*} type 事件类型
 * @param {*} layerFilter 图层山筛选函数
 * @param {*} cb1 选中要素回调
 * @param {*} cb2 未选中要素回调
 * @returns 事件Key
 */
export function mapOnFeature(map, type, layerFilter, cb1, cb2) {
    const key = map.on(type, function (e) {
        map.forEachFeatureAtPixel(e.pixel, function (feature, layer) {
            if (feature && layer) {
                cb1 && cb1(feature);
            } else {
                cb2 && cb2();
            }
        }, {
            layerFilter: layerFilter,
            hitTolerance: 5
        });
    });
    return key;
}

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5 进行缓冲区分析

import * as turf from "@turf/turf";
 
// 图层筛选
lFilter(layer) {
      // return layer;
      return layer.get("title") === "草图图层";
},
 
// 进行缓冲区分析
bufferF(feature) {
      const geometry = feature.getGeometry();
      const type = geometry.getType();
      geometry.transform("EPSG:3857", "EPSG:4326");
      const coords = geometry.getCoordinates();
 
      const tf = mCoords2TurfGeom[type](coords);
      // 缓冲区分析，turf必须使用wgs84经纬度坐标
      const tbf = turf.buffer(tf, this.mBuffer.distance, {
        units: this.mBuffer.unit,
      });
      const obf = new GeoJSON().readFeature(tbf);
 
      obf.getGeometry().transform("EPSG:4326", "EPSG:3857");
      geometry.transform("EPSG:4326", "EPSG:3857");
      this.pDrawLayer.getSource().addFeature(obf);
},
 
mBufferKey = mapOnFeature(this.pMap,"singleclick",this.lFilter,this.bufferF);

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6 实现界面及效果图