Vue+Openlayers实现遮罩效果

参考:
openlayers实现四周遮罩，特定区域透明效果_openlayers掩膜效果_月影星云的博客-CSDN博客

<template>
	<div id="Map" class="Map"></div>
</template>
<script>
import "ol/ol.css";
import { Map, View, Feature } from "ol";
import { XYZ, Vector as VectorSource } from "ol/source";
import { Tile as TileLayer, Vector as VectorLayer } from "ol/layer"; 
import { GeoJSON } from "ol/format";
import LinearRing from 'ol/geom/LinearRing.js';
import { fromExtent } from "ol/geom/Polygon";
import { Style, Stroke, Fill } from "ol/style";
import axios from 'axios'

export default {
    name: "MaskMap",
    data() {
        return {
            map: null,
        }
    },
    mounted(){
        this.initMap();
    },
    methods: {
        //初始化地图
        initMap(){
            var layers = [
                new TileLayer({
                    source: new XYZ({
                       // 灰色底图 wgs84
                        url: "http://map.geoq.cn/arcgis/rest/services/ChinaOnlineStreetGray/MapServer/tile/{z}/{y}/{x}"
                    })
                })
            ];
            //地图对象
            this.map = new Map({
                target: "Map",
                view: new View({
                    projection: "EPSG:4326",
                    center: [113.688548,34.761685],
                    zoom: 7,
                }),
                layers: layers,
                overlays: [],
            });
            //创建蒙层，凸显河南区域
            this.showHenanArea();
        },
        //创建蒙层，凸显河南区域
        showHenanArea(){ 
            let initLayer = new VectorLayer({
                zIndex: 3,
                source: new VectorSource(),
                style: new Style({
                    fill: new Fill({
                        color:"rgba( 255, 255, 255, 0.7)",
                    }),
                    stroke: new Stroke({
                        color:"#f4b49f",
                        width:3
                    })
                })
            });
            this.map.addLayer(initLayer);
            axios.get('https://geo.datav.aliyun.com/areas_v3/bound/geojson?code=410000').then(({ data }) => {
                this.addConver(initLayer, data);
            });
        },
        //添加遮罩
        addConver(converLayer, data) {
            const fts = new GeoJSON().readFeatures(data);
            const ft = fts[0];
            const converGeom = this.erase(ft.getGeometry());
            const convertFt = new Feature({
                geometry: converGeom,
            });
            converLayer.getSource().addFeature(convertFt);
        },
        //擦除操作，生产遮罩范围
        erase(geom) {
            const extent = [-180, -90, 180, 90];
            const polygonRing = fromExtent(extent);
            const coords = geom.getCoordinates();
            coords.forEach(coord => {
                const linearRing = new LinearRing(coord[0]);
                polygonRing.appendLinearRing(linearRing);
            });
            return polygonRing;
        }
    }
}
</script>
<style>
    html, body, #app, .Map{
        width: 100%;
        height: 100%;
    }
</style>