https://developers.weixin.qq.com/miniprogram/dev/component/canvas.html

  toggleScreenShotMode() {
    console.log("点击截屏")
    const videoContext = wx.createVideoContext('ulVideo', this);
    const query = wx.createSelectorQuery();
    query.select('#videoCanvas')
      .fields({
        node: true,
        size: true
      })
      .exec((res) => {
        console.log(res);
        const canvas = res[0].node;
        const canvasContext = canvas.getContext('2d');
        const width = res[0].width;
        const height = res[0].height;
        canvas.width = width;
        canvas.height = height;
        videoContext.pause();
  
        console.log('currentTime =', this.data.currentTime);
        videoContext.seek(this.data.currentTime);
        setTimeout(() => {
          wx.createSelectorQuery().select('#ulVideo').context().exec((res) => {
            console.log(res);
            const video = res[0].context;
            canvasContext.clearRect(0, 0, width, height);
            canvasContext.drawImage(video, 0, 0, width, height);
  
            wx.canvasToTempFilePath({
              canvas: canvas,
              fileType: 'jpg',
              success: (res) => {
                console.log('截屏成功', res.tempFilePath);
                // 获取图像数据
                wx.getFileSystemManager().readFile({
                  filePath: res.tempFilePath,
                  encoding: 'base64',
                  success: (fileRes) => {
                    const base64Image = 'data:image/png;base64,' + fileRes.data;
                    this.addImageToReport(res.tempFilePath, base64Image);
                  },
                  fail: (err) => {
                    console.error('读取图像数据失败：', err);
                  },
                });
              },
              fail: (err) => {
                console.error('截屏失败', err);
              }
            });
          });
        }, 500);
      });
  },