cesium 图层构建的那些事 （四）

我们通过构建百度地图容器类

```javascript

import {ImageryLayer} from "../ImageryLayer";

const urls:any = {

digital:"http://online{s}.map.bdimg.com/onlinelabel/?qt=tile&x={x}&y={y}&z={z}&styles=pl&scaler=1&p=1",//电子地图

image:"http://shangetu{s}.map.bdimg.com/it/u=x={x};y={y};z={z};v=009;type=sate&fm=46",//影像地图

mark:"http://online{s}.map.bdimg.com/tile/?qt=tile&x={x}&y={y}&z={z}&styles=sl&v=020",//注记

xxx:'http://api{s}.map.bdimg.com/customimage/tile?&x={x}&y={y}&z={z}&scale=1&customid={style}'

}

//百度地图

export class BDImageryLayer extends ImageryLayer{

public imageryProvider:any;//影像提供者

constructor(option:any={}){

super(option.name);

const url:string = urls[option.mold] || urls.digital;

option = {url,...option};

this.type = "BDImageryLayer";//重写类型

this.imageryProvider = new BaiduImageryProvider(option);

this.cesiumLayer = new Cesium.ImageryLayer(this.imageryProvider);

}

}

class BaiduImageryProvider{

public _errorEvent:any;

public _tileWidth:any;

public _tileHeight:any;

public _maximumLevel:any;

public _minimumLevel:any;

public _tilingScheme:any;

public _rectangle:any;

public _tileDiscardPolicy:any;

public _resource:any;

public _credit:any;

public _readyPromise:any;

constructor(options:any){

this._errorEvent = new Cesium.Event();

this._tileWidth = 256;

this._tileHeight = 256;

this._maximumLevel = 18;

this._minimumLevel = 1;

var southwestInMeters = new Cesium.Cartesian2(-33554054, -33746824);

var northeastInMeters = new Cesium.Cartesian2(33554054, 33746824);

this._tilingScheme = new Cesium.WebMercatorTilingScheme({

rectangleSouthwestInMeters: southwestInMeters,

rectangleNortheastInMeters: northeastInMeters

});

this._rectangle = this._tilingScheme.rectangle;

var resource = Cesium.Resource.createIfNeeded(options.url);

this._resource = resource;

this._tileDiscardPolicy = undefined;

 更多参考 https://xiaozhuanlan.com/topic/7254138609