点聚合

在Cesium相关项目开发过程中，当加载大量的点位后对底图有遮挡，需要使用点聚合功能，因此在聚合时需要动态更新聚合图标上被聚合的点位的数量。

实现效果

效果不是太理想，我用来测试的POI数据密度太大了。

https://blog.csdn.net/weixin_45782925/article/details/123054390

实现代码

最开始图片显示不完全修改combineIconAndLabel(url, label, size)中传入size的大小总算是显示出来了，也可能是自定义的图片有问题。参考文章在上面，记录一下。

<template>
  <div class="point-gather">
    <Map />
    <div class="gather">
      <div class="gather-con">
        <div class="box">
          <div class="txt">POI 点的聚合</div>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
import Map from "@/components/cesiumCommon/DTGlobeDark.vue";
import { DTGlobe } from "@/components/cesiumCommon/globe";

export default {
  components: { Map },
  data() {
    return {};
  },
  mounted() {
    this.Initial();
  },
  methods: {
    Initial() {
      let viewer = DTGlobe.viewer;
      viewer.camera.flyTo({
        destination: Cesium.Cartesian3.fromDegrees(
          114.32536,
          30.569676,
          5000.0
        ),
      });
      this.initCluster(viewer);
      //开启深度检测
      viewer.scene.globe.depthTestAgainstTerrain = true;
    },
    initCluster(viewer) {
      let that = this;
      new Cesium.GeoJsonDataSource.load("./data/人口岗位_质心.geojson").then(
        (dataSource) => {
          viewer.dataSources.add(dataSource);

          // 设置聚合参数
          dataSource.clustering.enabled = true;
          dataSource.clustering.pixelRange = 30;
          dataSource.clustering.minimumClusterSize = 2;

          // foreach用于调用数组的每个元素，并将元素传递给回调函数。
          dataSource.entities.values.forEach((entity) => {
            // 将点拉伸一定高度，防止被地形压盖
            entity.position._value.z += 50.0;
            // 使用大小为64*64的icon，缩小展示poi
            entity.billboard = {
              image: require("@/assets/imgs/point/报亭.png"),
              width: 32,
              height: 32,
            };
            // entity.label = {
            //   // text: "POI",
            //   font: "bold 15px Microsoft YaHei",
            //   // 竖直对齐方式
            //   verticalOrigin: Cesium.VerticalOrigin.CENTER,
            //   // 水平对齐方式
            //   horizontalOrigin: Cesium.HorizontalOrigin.LEFT,
            //   // 偏移量
            //   pixelOffset: new Cesium.Cartesian2(15, 0),
            // };
          });

          // 添加监听函数
          dataSource.clustering.clusterEvent.addEventListener(function (
            clusteredEntities,
            cluster
          ) {
            // 关闭自带的显示聚合数量的标签
            cluster.label.show = false;
            cluster.billboard.show = true;
            cluster.billboard.id = cluster.label.id;
            cluster.billboard.verticalOrigin = Cesium.VerticalOrigin.BOTTOM;
            // console.log("-----", cluster);
            // 根据聚合数量的多少设置不同层级的图片以及大小
            if (clusteredEntities.length >= 50) {
              cluster.billboard.image = that.combineIconAndLabel(
                require("@/assets/imgs/point/circ1.png"),
                clusteredEntities.length,
                192
              );
              cluster.billboard.width = 72;
              cluster.billboard.height = 72;
            } else if (clusteredEntities.length >= 40) {
              cluster.billboard.image = that.combineIconAndLabel(
                require("@/assets/imgs/point/circ2.png"),
                clusteredEntities.length,
                192
              );
              cluster.billboard.width = 56;
              cluster.billboard.height = 56;
            } else if (clusteredEntities.length >= 20) {
              cluster.billboard.image = that.combineIconAndLabel(
                require("@/assets/imgs/point/circ3.png"),
                clusteredEntities.length,
                192
              );
              cluster.billboard.width = 48;
              cluster.billboard.height = 48;
            } else {
              cluster.billboard.image = that.combineIconAndLabel(
                require("@/assets/imgs/point/circ4.png"),
                clusteredEntities.length,
                192
              );
              cluster.billboard.width = 40;
              cluster.billboard.height = 40;
            }
          });
        }
      );
    },
    /**
     * @description: 将图片和文字合成新图标使用
     * @param {*} url：图片地址
     * @param {*} label：文字
     * @param {*} size：画布大小
     * @return {*} 返回canvas
     */
    combineIconAndLabel(url, label, size) {
      // 创建画布对象
      let canvas = document.createElement("canvas");
      canvas.width = size;
      canvas.height = size;

      let ctx = canvas.getContext("2d");
      let promise = new Cesium.Resource.fetchImage(url).then((image) => {
        // 异常判断
        try {
          ctx.drawImage(image, -5, -5);
        } catch (e) {
          console.log(e);
        }
        // console.log("-----", ctx);
        // 渲染字体
        ctx.fillStyle = Cesium.Color.WHITE.toCssColorString();
        ctx.font = "bold 50px Microsoft YaHei";
        ctx.textAlign = "center";
        ctx.textBaseline = "middle";
        ctx.fillText(label, size / 2, size / 2);

        return canvas;
      });
      return promise;
    },
  },
};
</script>

<style lang="scss" scoped>
.point-gather {
  width: 100%;
  height: 100%;
  .gather {
    position: absolute;
    z-index: 99;
    &-con {
      padding: 5px;
      .box {
        border-radius: 6px;
        background: #304156b3;
        .txt {
          padding: 10px;
        }
      }
    }
  }
}
</style>