在有些业务中，对场景中的广告牌样式要求比较高，需要动态显示一些数据，这个时候，我们可以通过将复杂背景样式制作成图片，通过canvas绘制图片和动态数据，从而达到比较好的显示效果。
1 CanvasMarker 类封装
CanvasMarker.js
/** @Description:* @Author: maizi* @Date: 2022-05-27 11:36:22* @LastEditTime: 2024-07-23 15:34:06* @LastEditors: maizi*/
const merge = require('deepmerge')const defaultStyle = {scale: 0.2,text: '0.0'
}
const monitorPanel = require('@/assets/img/monitorPanel.png')class CanvasMarker {constructor(viewer, coords, options = {}) {this.viewer = viewer;this.coords = coords;this.options = options;this.props = this.options.props;this.baseHeight = this.coords[2] || 10;this.style = merge(defaultStyle, this.options.style || {});this.entity = null;this.canvas = nullthis.init();}init() {let img = new Image();img.src = monitorPanel;img.onload = ()=> {this.picture = img;this.canvas = this.createCanvas()}this.entity = new Cesium.Entity({type: "canvas_point",props: this.props,position:Cesium.Cartesian3.fromDegrees(this.coords[0], this.coords[1], this.baseHeight),billboard: {image: new Cesium.CallbackProperty(() => {return this.canvas.toDataURL("image/png");}),scale:new Cesium.CallbackProperty(() => {return this.style.scale}),color: new Cesium.Color(1, 1, 1),disableDepthTestDistance: Number.POSITIVE_INFINITY,},});}createCanvas() {let canvas = null;if (this.canvas) {canvas = this.canvas} else {canvas = document.createElement("canvas");canvas.width = 512;canvas.height = 329;}let ctx = canvas.getContext("2d");ctx.clearRect(0, 0, canvas.width, canvas.height);ctx.drawImage(this.picture, 0, 0);ctx.fillStyle = "rgb(255, 255, 255)",ctx.font = "80px sans-serif",ctx.textBaseline = "middle",ctx.fillText("温度：", 50, canvas.height / 2);ctx.fillText(this.style.text, 270, canvas.height / 2);ctx.fillText("℃", 380, canvas.height / 2);// // 导出canvas为图片// var dataURL = canvas.toDataURL("image/png");// var link = document.createElement('a');// link.download = 'canvas-image.png';// link.href = dataURL;// link.click();return canvas;}setSelect(enabled) {if (enabled) {this.addPoint()} else {this.removePoint()}}addPoint() {this.point = new Cesium.Entity({position: Cesium.Cartesian3.fromDegrees(this.coords[0], this.coords[1], this.baseHeight),point: {color: Cesium.Color.DARKBLUE.withAlpha(.4),pixelSize: 6,outlineColor: Cesium.Color.YELLOW.withAlpha(.8),outlineWidth: 4,disableDepthTestDistance: Number.POSITIVE_INFINITY} }); this.viewer.entities.add(this.point)}removePoint() {if (this.point) {this.viewer.entities.remove(this.point)this.point = null}}updateStyle(style) {this.style = merge(this.style, style || {});this.createCanvas()}
}export {CanvasMarker
}
2 完整示例代码
MapWorks.js
import GUI from 'lil-gui';
// 初始视图定位在中国
import { CanvasMarker } from './CanvasMarker'Cesium.Camera.DEFAULT_VIEW_RECTANGLE = Cesium.Rectangle.fromDegrees(90, -20, 110, 90);
//天地图key
const key = '39673271636382067f0b0937ab9a9677'let viewer = null;
let eventHandler = null;
let canvasLayer = null
let canvasList = []
let selectGraphic = null
let gui = nullfunction 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 = trueviewer.scene.postProcessStages.fxaa.enabled = trueif (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()// 鼠标事件initClickEvent()//调试window.viewer = viewer
}function initClickEvent() {eventHandler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);initLeftClickEvent()initMouseMoveEvent()
}function initLeftClickEvent() {eventHandler.setInputAction((e) => {if (selectGraphic) {selectGraphic.setSelect(false)selectGraphic = null}if (gui) {gui.destroy()}let pickedObj = viewer.scene.pick(e.position);if (pickedObj && pickedObj.id) {if (pickedObj.id.type === 'canvas_point') {selectGraphic = getGraphicById(pickedObj.id.id)if (selectGraphic) {selectGraphic.setSelect(true)initGui()}}}},Cesium.ScreenSpaceEventType.LEFT_CLICK)
}function initMouseMoveEvent() {eventHandler.setInputAction((e) => {const pickedObj = viewer.scene.pick(e.endPosition);if (pickedObj && pickedObj.id) {if (pickedObj.id.type === 'canvas_point') {// 改变鼠标状态viewer._element.style.cursor = "";document.body.style.cursor = "pointer";} else {viewer._element.style.cursor = "";document.body.style.cursor = "default";}} else {viewer._element.style.cursor = "";document.body.style.cursor = "default";}},Cesium.ScreenSpaceEventType.MOUSE_MOVE)
}function getGraphicById(id) {let graphic = nullfor (let i = 0; i < canvasList.length; i++) {if (canvasList[i].entity.id === id) {graphic = canvasList[i]break} }return graphic
}
function initGui() {let params = {...selectGraphic.style}gui = new GUI()let layerFolder = gui.title('参数设置')layerFolder.add(params, 'scale', 0.1, 2).step(0.1).onChange(function (value) {selectGraphic.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'})canvasLayer = new Cesium.CustomDataSource('canvasMarker')viewer.dataSources.add(canvasLayer)}function loadCanvasMarker(points) {points.forEach(item => {const canvasMarker = new CanvasMarker(viewer, item)canvasList.push(canvasMarker)canvasLayer.entities.add(canvasMarker.entity)});viewer.flyTo(canvasLayer)updateText()
}function updateText() {setInterval(()=>{canvasList.forEach((item) => {const text = Math.floor(30 * Math.random())item.updateStyle({text: text})})}, 2000)
}function removeAll() {viewer.imageryLayers.removeAll();
}function destroy() {viewer.entities.removeAll();viewer.imageryLayers.removeAll();viewer.destroy();
}export {initMap,loadCanvasMarker,destroy
}CanvasMarker.vue
<!--* @Description: * @Author: maizi* @Date: 2023-04-07 17:03:50* @LastEditTime: 2023-04-11 18:07:29* @LastEditors: maizi
--><template><div id="container"></div>
</template><script>
import * as MapWorks from './js/MapWorks'
export default {name: 'CanvasMarker',mounted() {this.init();},methods:{init(){let container = document.getElementById("container");MapWorks.initMap(container)//创建告警点let points = [[104.074822, 30.659807, 60],[104.076822, 30.653807, 60],[104.075822, 30.652807, 60],[104.072822, 30.654807, 60]];MapWorks.loadCanvasMarker(points)}},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);
}</style>3 运行效果
