本篇介紹一下使用 vue3-openlayers marker 光暈擴散（光環擴散）（postrender 事件和 render 方法）

1 需求

• marker 光暈擴散（光環擴散）

2 分析

marker 光暈擴散（光環擴散）使用 postrender 事件和 render 方法
關于即時渲染的知識點請看上篇《openlayers marker 光暈擴散（光環擴散）（postrender 事件和 render 方法）》

3 實現

3.1 實現一(光環)

<template><ol-map:loadTilesWhileAnimating="true":loadTilesWhileInteracting="true"style="width: 100%; height: 100%"ref="mapRef"><ol-view ref="view" :center="center" :zoom="zoom" :projection="projection" /><ol-tile-layer><ol-source-tianditulayerType="img":projection="projection":tk="key":hidpi="true"ref="sourceRef"></ol-source-tianditu></ol-tile-layer><ol-tile-layer><ol-source-tianditu:isLabel="true"layerType="img":projection="projection":tk="key":hidpi="true"></ol-source-tianditu></ol-tile-layer><ol-vector-layer ref="vectorLayerRef" @postrender="handlePostRender"><ol-source-vector><ol-feature><ol-geom-point :coordinates="[110, 30]"></ol-geom-point><ol-style><ol-style-icon :src="iconSrc" :scale="0.05"></ol-style-icon></ol-style></ol-feature><ol-feature><ol-geom-point :coordinates="[112, 31]"></ol-geom-point><ol-style><ol-style-icon :src="iconSrc" :scale="0.05"></ol-style-icon></ol-style></ol-feature></ol-source-vector></ol-vector-layer></ol-map><div class="toolbar"><el-button type="primary" @click="handleClick">{{ animationFlag ? '停止' : '開始' }}</el-button></div>
</template><script setup lang="ts">
import iconSrc from '@/assets/image/truck.png';
import { getVectorContext } from 'ol/render.js';
import { easeOut } from 'ol/easing.js';
import { Circle, Stroke, Style } from 'ol/style';const center = ref([121, 31]);
const projection = ref('EPSG:4326');
const zoom = ref(5);
const mapRef = ref();
const key = '替換為天地圖key';
const sourceRef = ref(null);
const vectorLayerRef = ref(null);
const animationFlag = ref(false);
const duration = ref([3000, 1000]);
const start = ref([0, 0]);const handleClick = () => {if (!animationFlag.value) {start.value = start.value.map(i => Date.now());vectorLayerRef.value.vectorLayer.changed();}animationFlag.value = !animationFlag.value;
};const handlePostRender = e => {if (animationFlag.value) {const time = e.frameState.time;vectorLayerRef.value.vectorLayer.getSource().getFeatures().forEach((f, idx) => {// 時間戳差（毫秒）let elapsedTime = time - start.value[idx];if (elapsedTime >= duration.value[idx]) {start.value[idx] = Date.now();elapsedTime = duration.value[idx];}// 獲取矢量上下文const vectorContext = getVectorContext(e);// elapsedRatio值0到1之間const elapsedRatio = elapsedTime / duration.value[idx];const radius = easeOut(elapsedRatio) * 25 + 5;const opacity = easeOut(1 - elapsedRatio);const style = new Style({image: new Circle({radius: radius,stroke: new Stroke({color: 'rgba(255, 0, 0, ' + opacity + ')',width: 1 + opacity})})});// 將feature渲染到畫布中。vectorContext.drawFeature(f.clone(), style);});mapRef.value.map.render();}
};
</script>
<style scoped lang="scss">
.toolbar {position: absolute;top: 20px;left: 100px;display: flex;justify-content: center;align-items: center;
}
</style>

3.2 實現二(光暈)

<template><ol-map:loadTilesWhileAnimating="true":loadTilesWhileInteracting="true"style="width: 100%; height: 100%"ref="mapRef"><ol-view ref="view" :center="center" :zoom="zoom" :projection="projection" /><ol-tile-layer><ol-source-tianditulayerType="img":projection="projection":tk="key":hidpi="true"ref="sourceRef"></ol-source-tianditu></ol-tile-layer><ol-tile-layer><ol-source-tianditu:isLabel="true"layerType="img":projection="projection":tk="key":hidpi="true"></ol-source-tianditu></ol-tile-layer><ol-vector-layer ref="vectorLayerRef" @postrender="handlePostRender"><ol-source-vector><ol-feature><ol-geom-point :coordinates="[110, 30]"></ol-geom-point></ol-feature><ol-feature><ol-geom-point :coordinates="[112, 31]"></ol-geom-point></ol-feature></ol-source-vector></ol-vector-layer><ol-vector-layer ><ol-source-vector><ol-feature><ol-geom-point :coordinates="[110, 30]"></ol-geom-point><ol-style><ol-style-icon :src="iconSrc" :scale="0.05"></ol-style-icon></ol-style></ol-feature><ol-feature><ol-geom-point :coordinates="[112, 31]"></ol-geom-point><ol-style><ol-style-icon :src="iconSrc" :scale="0.05"></ol-style-icon></ol-style></ol-feature></ol-source-vector></ol-vector-layer></ol-map><div class="toolbar"><el-button type="primary" @click="handleClick">{{ animationFlag ? '停止' : '開始' }}</el-button></div>
</template><script setup lang="ts">
import iconSrc from '@/assets/image/truck.png';
import { getVectorContext } from 'ol/render.js';
import { easeOut } from 'ol/easing.js';
import { Circle, Fill, Stroke, Style } from 'ol/style';const center = ref([121, 31]);
const projection = ref('EPSG:4326');
const zoom = ref(5);
const mapRef = ref();
const key = '替換為天地圖key';
const sourceRef = ref(null);
const vectorLayerRef = ref(null);
const animationFlag = ref(false);
const duration = ref([3000, 1000]);
const start = ref([0, 0]);const handleClick = () => {if (!animationFlag.value) {start.value = start.value.map(i => Date.now());vectorLayerRef.value.vectorLayer.changed();}animationFlag.value = !animationFlag.value;
};const handlePostRender = e => {if (animationFlag.value) {const time = e.frameState.time;vectorLayerRef.value.vectorLayer.getSource().getFeatures().forEach((f, idx) => {// 時間戳差（毫秒）let elapsedTime = time - start.value[idx];if (elapsedTime >= duration.value[idx]) {start.value[idx] = Date.now();elapsedTime = duration.value[idx];}// 獲取矢量上下文const vectorContext = getVectorContext(e);// elapsedRatio值0到1之間const elapsedRatio = elapsedTime / duration.value[idx];const radius = easeOut(elapsedRatio) * 25 + 5;const opacity = easeOut(1 - elapsedRatio);const style = new Style({image: new Circle({radius: radius,fill: new Fill({color: 'rgba(228, 147, 87, ' + opacity + ')'}),stroke: new Stroke({color: 'rgba(255, 0, 0, ' + opacity + ')',width: 1 + opacity})})});// 將feature渲染到畫布中。vectorContext.drawFeature(f.clone(), style);});mapRef.value.map.render();}
};
</script>
<style scoped lang="scss">
.toolbar {position: absolute;top: 20px;left: 100px;display: flex;justify-content: center;align-items: center;
}
</style>