//展示视频封面vue
videoLoad(o) {
    //获取video标签
    let video_dom = document.getElementById("player-video");
    //定义缩放比例
    let scale = 1;
    //创建canvas画布
    let canvas = document.createElement("canvas");
    //canvas宽高为video宽高*缩放比例
    canvas.width = video_dom.videoWidth * scale;
    canvas.height = video_dom.videoHeight * scale;
    this.width=canvas.width;
    //canvas画出视频封面
    canvas
        .getContext("2d")
        .drawImage(video_dom, 0, 0, canvas.width, canvas.height);
    //canvas转base64
    let src = canvas.toDataURL("image/png");
    console.log(canvas.width,22,canvas.height);
    //赋值到playerOptions.poster
    // this.poster = src;
  },