downloadImage(imgsrc, name) {
        //下载图片地址和图片名
        var image = new Image();
        // 解决跨域 Canvas 污染问题
        image.setAttribute("crossOrigin", "anonymous");
        image.onload = function() {
          var canvas = document.createElement("canvas");
          canvas.width = image.width;
          canvas.height = image.height;
          var context = canvas.getContext("2d");
          context.drawImage(image, 0, 0, image.width, image.height);
          var url = canvas.toDataURL("image/png"); //得到图片的base64编码数据
  
          var a = document.createElement("a"); // 生成一个a元素
          var event = new MouseEvent("click"); // 创建一个单击事件
          a.download = name || "photo"; // 设置图片名称
          a.href = url; // 将生成的URL设置为a.href属性
          a.dispatchEvent(event); // 触发a的单击事件
        };
        image.src = imgsrc;
      },
      downs() {
        this.downloadImage(this.imageUrl, "couponqrcode");
      },

转自：https://blog.csdn.net/bamboozjy/article/details/81631487