我也遇到相同问题

wxml
<canvas id="rafCanvas" type="2d" style="display:none;"></canvas>
ts
onLoad(options) {
    const eventChannel = this.getOpenerEventChannel();
    // 监听acceptDataFromOpenerPage事件，获取上一页面通过eventChannel传送到当前页面的数据
    eventChannel.on('acceptDataFromOpenerPage', (data: { path: string; size: number }) => {
      // 通过 SelectorQuery 获取 Canvas 节点
      wx.createSelectorQuery()
        .select('#rafCanvas')
        .fields({
          node: true,
        })
        .exec(res => {
          canvas = res[0].node;
          wx.getSystemInfo({
            success: res => {
              this.setData({
                windowHeight: res.windowHeight,
                windowWidth: res.windowWidth,
                pixelRatio: res.pixelRatio,
              });
              this.analysis(data);
            },
            fail: err => {
              console.log(err);
            },
          });
        });
    });
  },