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cesium 点聚合

时间：2024-08-02 15:57:48浏览次数：18  
标签：canvas 聚合 ctx num let cesium id size

撒点功能是gis项目中，最常用的功能。如果点位比较密集，就会出现点位图标重叠问题，如果点位过多，会影响绘制的性能，就会导致页面出现卡顿等问题。点聚合是一种比较好的解决方式。本篇对Entity图元的点聚合进行封装，在数据量不是太大的情况下，可以取得比较好的显示效果，如果数据量比较大，使用Entity图元的点聚合仍然会出现性能问题，可以通过对primitive点图元进行封装，支持更大体量的点聚合，后续primitive图元篇重再介绍。

1 EntityCluster 类

前面的篇章介绍过CustomDataSource类，它有一个属性clustering 可以完成改数据源的点聚合的功能。clustering是一个EntityCluster类对象，定义屏幕空间对象（广告牌、点、标签）如何聚集。其参数如下：

通过对EntityCluster类的聚合事件clusterEvent的监听，可以动态的设置聚合后的点样式。clusterEvent回调函数返回一个点位集合和聚合后的entity图元。使用示例如下：

dataSource.clustering.clusterEvent.addEventListener(function(entities, cluster) {
    cluster.label.show = false;
    cluster.billboard.show = true;
    cluster.billboard.image = this.getCluserCanvasImage(entities.length);
});

2 点聚合样式

根据聚合点位集合的大小，可以设置聚合点图标的大小和颜色，这里通过canvas动态绘制聚合点图标的方式，给出两种点聚合样式。如果对聚合样式有更高的要求，可以通过外部传入样式图片的方式，这里不再详细说明。

2.1 点聚合样式1
getCluserCanvasImage(num) {
		if (this.cluserCanvasImages[num]) {
			return this.cluserCanvasImages[num];
		}
		//创建cavas
		let canvas = document.createElement("canvas");
		//canvas大小
		let size = 12 * (num + "").length + 50;
		canvas.width = canvas.height = size;
		//获取canvas 上下文
		let ctx = canvas.getContext("2d");
		//绘制
		ctx.beginPath();
		ctx.globalAlpha = 0.5;
		(ctx.fillStyle = this.getCluseColor(num)),
			ctx.arc(size / 2, size / 2, size / 2 - 5, 0, 2 * Math.PI),
			ctx.fill(),
			ctx.beginPath(),
			(ctx.globalAlpha = 0.8),
			(ctx.fillStyle = this.getCluseColor(num)),
			ctx.arc(size / 2, size / 2, size / 2 - 10, 0, 2 * Math.PI),
			ctx.fill(),
			(ctx.font = "20px alpht"),
			(ctx.globalAlpha = 1),
			(ctx.fillStyle = "rgb(255,255,255)");
		let offset = size / 2 - (12 * num.toString().length) / 2;
		ctx.fillText(num, offset, size / 2 + 7);
		this.cluserCanvasImages[num] = canvas;
		return canvas;
	}
2.2 点聚合样式2
getCluserCanvasImage2(num) {
		if (this.cluserCanvasImages[num]) {
			return this.cluserCanvasImages[num];
		}
		//创建cavas
		let canvas = document.createElement("canvas");
		//canvas大小
		let size = 12 * (num + "").length + 50;
		canvas.width = canvas.height = size;
		//获取canvas 上下文
		let ctx = canvas.getContext("2d");
		//绘制
		ctx.translate(size / 2, size / 2);
		ctx.fillStyle = this.getCluseColor(num);

		const angle = Math.PI / 2;
		const dltAngle = Math.PI / 6;
		let startAngle = 0;
		let endAngle = 0;
		for (let i = 0; i < 3; i++) {
			ctx.beginPath();
			ctx.moveTo(0, 0);
			ctx.globalAlpha = 0.5;
			startAngle = endAngle + dltAngle;
			endAngle = startAngle + angle;
			ctx.arc(0, 0, size / 2 - 5, startAngle, endAngle);
			ctx.closePath();
			ctx.fill();
		}
		ctx.beginPath();
		ctx.moveTo(0, 0);
		ctx.globalAlpha = 1.0;
		ctx.arc(0, 0, size / 4, 0, 2 * Math.PI), ctx.fill();

		ctx.translate(-size / 2, -size / 2);
		ctx.font = "20px alpht";
		ctx.globalAlpha = 1;
		ctx.fillStyle = "rgb(255,255,255)";
		let offset = size / 2 - (12 * num.toString().length) / 2;
		ctx.fillText(num, offset, size / 2 + 7);
		this.cluserCanvasImages[num] = canvas;
		return canvas;
	}

3 ClusterLayer 类封装

ClusterLayer.js

/*
 * @Description:
 * @Author: maizi
 * @Date: 2022-05-27 11:36:22
 * @LastEditTime: 2024-07-23 16:48:10
 * @LastEditors: maizi
 */
const merge = require('deepmerge')
import carIcon from "@/assets/img/car-icon.png";
import selectCarIcon from "@/assets/img/car-s-icon.png";
const defaultStyle = {
	pixelRange: 40,
	minimumClusterSize: 2,
	image: carIcon,
	selectImage: selectCarIcon,
	scale: 0.7,
	type: 0,
	cluserColors: [
		{
			value: 40,
			color: "rgb(255,0,0)"
		},
		{
			value: 30,
			color: "rgb(255,0,255)"
		},
		{
			value: 20,
			color: "rgb(255,255,0)"
		},
		{
			value: 10,
			color: "rgb(0,255,255)"
		},
		{
			value: 1,
			color: "rgb(0,255,0)"
		}
	]
};
class ClusterLayer {
	constructor(options = {}) {
		this.options = options;
		this.style = merge(defaultStyle, this.options.style || {});
		this.layer = null;

		this.cluserCanvasImages = {};
		this.init();
	}
	init() {
		this.layer = new Cesium.CustomDataSource("clusterLayer");
		this.layer.clustering.enabled = true;
		this.layer.clustering.pixelRange = this.style.pixelRange;
		this.layer.clustering.minimumClusterSize = this.style.minimumClusterSize;
		this.setCanvasClusterEvent();
	}

	addDataToLayer(data) {
		data.forEach(item => {
			const entity = new Cesium.Entity({
				id: item.id ? item.id : Math.random().toString(36).substring(2),
				props: item,
				position: Cesium.Cartesian3.fromDegrees(item.coords[0], item.coords[1]),
				billboard: {
					image: this.style.image,
					scale: this.style.scale,
					disableDepthTestDistance: Number.POSITIVE_INFINITY
				}
			});
			entity.layer = this.layer;
			this.layer.entities.add(entity);
		});
	}
	
	setCanvasClusterEvent() {
		this.layer.clustering.clusterEvent.addEventListener((clusteredEntities, feature) => {
			feature.label.show = false;
			feature.layer = this.layer;
			feature.billboard.show = true;
			feature.billboard.id = feature.label.id;
			feature.billboard.verticalOrigin = Cesium.VerticalOrigin.BOTTOM;
			feature.billboard.disableDepthTestDistance = Number.POSITIVE_INFINITY;
			let image = null;
			switch (this.style.type) {
				case 0:
					image = this.getCluserCanvasImage(clusteredEntities.length);
					break;
				case 1:
					image = this.getCluserCanvasImage2(clusteredEntities.length);
					break;
			}
			feature.billboard.image = image;
		});
	}

	getCluserCanvasImage(num) {
		if (this.cluserCanvasImages[num]) {
			return this.cluserCanvasImages[num];
		}
		//创建cavas
		let canvas = document.createElement("canvas");
		//canvas大小
		let size = 12 * (num + "").length + 50;
		canvas.width = canvas.height = size;
		//获取canvas 上下文
		let ctx = canvas.getContext("2d");
		//绘制
		ctx.beginPath();
		ctx.globalAlpha = 0.5;
		(ctx.fillStyle = this.getCluseColor(num)),
			ctx.arc(size / 2, size / 2, size / 2 - 5, 0, 2 * Math.PI),
			ctx.fill(),
			ctx.beginPath(),
			(ctx.globalAlpha = 0.8),
			(ctx.fillStyle = this.getCluseColor(num)),
			ctx.arc(size / 2, size / 2, size / 2 - 10, 0, 2 * Math.PI),
			ctx.fill(),
			(ctx.font = "20px alpht"),
			(ctx.globalAlpha = 1),
			(ctx.fillStyle = "rgb(255,255,255)");
		let offset = size / 2 - (12 * num.toString().length) / 2;
		ctx.fillText(num, offset, size / 2 + 7);
		this.cluserCanvasImages[num] = canvas;
		return canvas;
	}

	getCluserCanvasImage2(num) {
		if (this.cluserCanvasImages[num]) {
			return this.cluserCanvasImages[num];
		}
		//创建cavas
		let canvas = document.createElement("canvas");
		//canvas大小
		let size = 12 * (num + "").length + 50;
		canvas.width = canvas.height = size;
		//获取canvas 上下文
		let ctx = canvas.getContext("2d");
		//绘制
		ctx.translate(size / 2, size / 2);
		ctx.fillStyle = this.getCluseColor(num);

		const angle = Math.PI / 2;
		const dltAngle = Math.PI / 6;
		let startAngle = 0;
		let endAngle = 0;
		for (let i = 0; i < 3; i++) {
			ctx.beginPath();
			ctx.moveTo(0, 0);
			ctx.globalAlpha = 0.5;
			startAngle = endAngle + dltAngle;
			endAngle = startAngle + angle;
			ctx.arc(0, 0, size / 2 - 5, startAngle, endAngle);
			ctx.closePath();
			ctx.fill();
		}
		ctx.beginPath();
		ctx.moveTo(0, 0);
		ctx.globalAlpha = 1.0;
		ctx.arc(0, 0, size / 4, 0, 2 * Math.PI), ctx.fill();

		ctx.translate(-size / 2, -size / 2);
		ctx.font = "20px alpht";
		ctx.globalAlpha = 1;
		ctx.fillStyle = "rgb(255,255,255)";
		let offset = size / 2 - (12 * num.toString().length) / 2;
		ctx.fillText(num, offset, size / 2 + 7);
		this.cluserCanvasImages[num] = canvas;
		return canvas;
	}

	getCluseColor(num) {
		for (let i = 0; i < this.style.cluserColors.length; i++) {
			let item = this.style.cluserColors[i];
			if (num >= item.value) {
				return item.color;
			}
		}
	}

	updateStyle(style) {
		this.style = merge(this.style, style);
		this.layer.clustering.pixelRange = this.style.pixelRange;
		this.layer.clustering.minimumClusterSize = this.style.minimumClusterSize;
	}

	setType(type) {
		this.style.type = type;
	}

	setSelectById(id, enabled) {
		if (this.layer) {
			const entity = this.layer.entities.getById(id);
			entity && (entity.billboard.image = enabled ? this.style.selectImage : this.style.image);
		}
	}

	getEntityById(id) {
		const entity = this.layer.entities.getById(id);
		return entity;
	}

	clear() {
		this.cluserCanvasImages = {};
		if (this.layer) {
			this.layer.entities.removeAll();
		}
	}
}

export { ClusterLayer };

4 完整示例代码

MapWorks.js

import GUI from 'lil-gui'; 
// 初始视图定位在中国
import { ClusterLayer } from './ClusterLayer'

Cesium.Camera.DEFAULT_VIEW_RECTANGLE = Cesium.Rectangle.fromDegrees(90, -20, 110, 90);

//天地图key
const key = '39673271636382067f0b0937ab9a9677'
const gui = new GUI();
const params = {
  pixelRange: 40,
  minimumClusterSize: 2
}

let viewer = null;
let clusterLayer = null
let eventHandler = null
let selectGraphic = null

function initMap(container) {
  viewer = new Cesium.Viewer(container, {
    animation: false,
    baseLayerPicker: false,
    fullscreenButton: false,
    geocoder: false,
    homeButton: false,
    infoBox: false,
    sceneModePicker: false,
    selectionIndicator: false,
    timeline: false,
    navigationHelpButton: false, 
    scene3DOnly: true,
    orderIndependentTranslucency: false,
    contextOptions: {
      webgl: {
        alpha: true
      }
    }
  })
  viewer._cesiumWidget._creditContainer.style.display = 'none'
  viewer.scene.fxaa = true
  viewer.scene.postProcessStages.fxaa.enabled = true
  if (Cesium.FeatureDetection.supportsImageRenderingPixelated()) {
    // 判断是否支持图像渲染像素化处理
    viewer.resolutionScale = window.devicePixelRatio
  }
  // 移除默认影像
  removeAll()
  // 地形深度测试
  viewer.scene.globe.depthTestAgainstTerrain = true
  // 背景色
  viewer.scene.globe.baseColor = new Cesium.Color(0.0, 0.0, 0.0, 0)
  // 太阳光照
  viewer.scene.globe.enableLighting = true;

  // 初始化图层
  initLayer()
  // 初始化鼠标事件
  initClickEvent()

   //gui面板
  initGui()

  //调试
  window.viewer = viewer
}

function initGui() {
  let layerFolder = gui.title('样式设置')
  layerFolder.add(params, 'pixelRange', 20, 200).step(1).onChange(function (value) {
    clusterLayer.updateStyle(params)
  })
  layerFolder.add(params, 'minimumClusterSize', 2, 10).step(1).onChange(function (value) {
    clusterLayer.updateStyle(params)
  })
}

function addTdtLayer(options) {
  let url = `https://t{s}.tianditu.gov.cn/DataServer?T=${options.type}&x={x}&y={y}&l={z}&tk=${key}`
  const layerProvider = new Cesium.UrlTemplateImageryProvider({
    url: url,
    subdomains: ['0','1','2','3','4','5','6','7'],
    tilingScheme: new Cesium.WebMercatorTilingScheme(),
    maximumLevel: 18
  });
  viewer.imageryLayers.addImageryProvider(layerProvider);
}

function initLayer() {
  addTdtLayer({
    type: 'img_w'
  })
  addTdtLayer({
    type: 'cia_w'
  })
  clusterLayer = new ClusterLayer()
  viewer.dataSources.add(clusterLayer.layer);
} 

function loadClusterData(data, options) {
  clusterLayer.clear()
  clusterLayer.setType(options.type)
  clusterLayer.addDataToLayer(data)
  viewer.flyTo(clusterLayer.layer);
}


function initClickEvent() {
  eventHandler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
  initLeftClickEvent()
  initMouseMoveEvent()
}

function initLeftClickEvent() {
  eventHandler.setInputAction((e) => {
    const pickedObj = viewer.scene.pick(e.position);
    if (selectGraphic) {
			clusterLayer.setSelectById(selectGraphic.id, false);
			selectGraphic = null;
		}
    if (pickedObj && pickedObj.id) {
			if (pickedObj.id instanceof Cesium.Entity) {
				//选中单个
				if (pickedObj.id.layer && pickedObj.id.layer.name === "clusterLayer") {
					selectGraphic = pickedObj.id;
					clusterLayer.setSelectById(selectGraphic.id, true);
				}
			} else if (pickedObj.id instanceof Array) {
				// 选中聚合
				if (pickedObj.id[0].layer && pickedObj.id[0].layer.name === "clusterLayer") {
					console.log("聚合点位信息=>", pickedObj.id);
				}
			}
		}
  },Cesium.ScreenSpaceEventType.LEFT_CLICK)
}

function initMouseMoveEvent() {
  eventHandler.setInputAction((e) => {
    const pickedObj = viewer.scene.pick(e.endPosition);
    if (pickedObj && pickedObj.id) {
      if (pickedObj.id instanceof Cesium.Entity || pickedObj.id instanceof Array) {
          // 改变鼠标状态
        viewer.enableCursorStyle = false;
        viewer._element.style.cursor = "";
        document.body.style.cursor = "pointer";
      }
    } else {
      // 改变鼠标状态
      viewer.enableCursorStyle = true;
      viewer._element.style.cursor = "";
      document.body.style.cursor = "default";
    }
  }, Cesium.ScreenSpaceEventType.MOUSE_MOVE);
}


function removeAll() {
  viewer.imageryLayers.removeAll();
}

function destroy() {
  viewer.entities.removeAll();
  viewer.imageryLayers.removeAll();
  viewer.destroy();
}

export {
  initMap,
  loadClusterData,
  destroy
}

ClusterLayer.vue

<!--
 * @Description: 
 * @Author: maizi
 * @Date: 2023-04-07 17:03:50
 * @LastEditTime: 2023-04-14 09:47:03
 * @LastEditors: maizi
-->

<template>
  <div id="container">
    <div class="pane_container">
      <el-button size="small" @click="changeType(0)">聚合样式1</el-button>
      <el-button size="small" @click="changeType(1)">聚合样式2</el-button>
    </div>
  </div>
</template>

<script>
import * as MapWorks from './js/MapWorks'
export default {
  name: 'ClusterLayer',
  mounted() {
    this.init();
  },
  methods:{
    init(){
      let container = document.getElementById("container");
      MapWorks.initMap(container)
    },
    changeType(type) {
      const data = [
      {
				coords: [104.06791968990645, 30.639931966652405],
				id: "ulqg4wpkado1",
			},
			{
				coords: [104.08286762001791, 30.651738427212116],
				id: "ulqg4wpkado2",
			},
			{
				coords: [104.05749321027527, 30.65012469539701],
				id: "ulqg4wpkado3",
			},
			{
				coords: [104.08726215231565, 30.64326919178345],
				id: "ulqg4wpkado4",

			},
			{
				coords: [104.05035209594628, 30.63767262782807],
				id: "ulqg4wpkado5",
			},
			{
				coords: [104.06333112463464, 30.65974843756529],
				id: "ulqg4wpkado6",
			},
			{
				coords: [104.05830951574102, 30.67804353001073],
				id: "ulqg4wpkado7",
			},
			{
				coords: [104.05817218349625, 30.669883306472084],
				id: "ulqg4wpkado8",
			},
			{
				coords: [104.05049441213879, 30.66347415161995],
				id: "ulqg4wpkado9",
			},
			{
				coords: [104.04463502177197, 30.676841811429426],
				id: "ulqg4wpkado10",
			},
			{
				coords: [104.03804322070602, 30.66933394719844],
				id: "ulqg4wpkado11",
			},
			{
				coords: [104.09535525896746, 30.657248119145248],
				id: "ulqg4wpkado12",
			},
			{
				coords: [104.08702274136078, 30.671537092255143],
				id: "ulqg4wpkado13",
			},
			{
				coords: [104.07828569455882, 30.65974271388589],
				id: "ulqg4wpkado14",
			},
			{
				coords: [104.07607075284544, 30.677677293114513],
				id: "ulqg4wpkado15",
			},
			{
				coords: [104.07594606111917, 30.670615773715657],
				id: "ulqg4wpkado16",
			}
      ]
      MapWorks.loadClusterData(data, {
        type: type
      })
    }
  },

  beforeDestroy(){
    //实例被销毁前调用，页面关闭、路由跳转、v-if和改变key值
    MapWorks.destroy();
  }
}
</script>

<style lang="scss" scoped>
#container{
  width: 100%;
  height: 100%;
  background: rgba(7, 12, 19, 1);
  overflow: hidden;
  background-size: 40px 40px, 40px 40px;
  background-image: linear-gradient(hsla(0, 0%, 100%, 0.05) 1px, transparent 0), linear-gradient(90deg, hsla(0, 0%, 100%, 0.05) 1px, transparent 0);
  .pane_container{
    position: absolute;
    left: 10px;
    top: 50px;
    padding: 10px 15px;
    border-radius: 4px;
    border: 1px solid rgba(128, 128, 128, 0.5);
    color: #ffffff;
    background: rgba(0, 0, 0, 0.4);
    box-shadow: 0 3px 14px rgb(128 128 128 / 50%);
    z-index: 2;
  }
}


</style>

5 运行结果

标签：canvas,聚合,ctx,num,let,cesium,id,size
From： https://blog.csdn.net/hongxianqiang/article/details/140872536

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