beforeUpload(file) {
      // 文件上传前钩子
      var result = _g.checkUploadImg(file, this.rules);
      if (result !== true) {
        _g.message(result, "error");
        return false;
      }
      const isJpgOrPng =
        file.type === "image/jpeg" ||
        file.type === "image/png" ||
        file.type === "image/jpg"; //图片格式是否为png或jpg
      const isLt5M = file.size / 1024 / 1024 < 5; //判断图片大小是否超过5MB
      if (isJpgOrPng) {
        if (!isLt5M) {
          this.$message.error("文件过大！");
          return false;
        }
        const _this = this;
        return new Promise(resolve => {
          const reader = new FileReader();
          const image = new Image();
          image.onload = async imageEvent => {
            const originWidth = image.width;
            const originHeight = image.height;
            const canvas = document.createElement("canvas");
            const context = canvas.getContext("2d");
            // 最大尺寸限制，可通过设置宽高来实现图片压缩程度
            let maxWidth = 800,
              maxHeight = 800;
            // 目标尺寸
            let targetWidth = originWidth,
              targetHeight = originHeight;
            // 图片尺寸超过800x800的限制
            if (originWidth > maxWidth || originHeight > maxHeight) {
              if (originWidth / originHeight > maxWidth / maxHeight) {
                // 更宽，按照宽度限定尺寸
                targetWidth = maxWidth;
                targetHeight = Math.round(
                  maxWidth * (originHeight / originWidth)
                );
              } else {
                targetHeight = maxHeight;
                targetWidth = Math.round(
                  maxHeight * (originWidth / originHeight)
                );
              }
            }
            canvas.width = targetWidth;
            canvas.height = targetHeight;
            context.clearRect(0, 0, targetWidth, targetHeight);
            context.fillRect(0, 0, canvas.width, canvas.height);
            context.save();
            context.drawImage(image, 0, 0, targetWidth, targetHeight);
            try {
              const res = await axios({
                method: "post", // 请求方式
                url: "/shrink", // 请求接口
                baseURL: "", // 运维配置的请求地址
                headers: {
                  Authorization:"" // 请求头参数，可以在登录后tiny上获取
                }, 
                data: file // 数据
              });
              let str = res.data.output.url.substring(22);
              const res2 = await axios({
                method: "get", // 请求方式
                url: str, // 请求接口
                baseURL: "", // 运维配置的请求地址
                responseType: "arraybuffer"
              });
              let url =
                "data:image/png;base64," +
                btoa(
                  new Uint8Array(res2.data).reduce(
                    (data, byte) => data + String.fromCharCode(byte),
                    ""
                  )
                );
              const blobData = _this.dataURItoBlob(url);
              resolve(blobData);
            } catch (error) {
              resolve();
              console.log(error);
            }
          };
          reader.onload = e => {
            image.src = e.target.result;
          };
          reader.readAsDataURL(file);
        });
      }
      return true;
    },