el-upload---上传/下载图片

          <el-upload
            ref="upload"
            :file-list="fileList"
            action="#"
            :auto-upload="false"
            :on-change="handleChange"
            :on-remove="handleRemove"
            :limit="2"
            list-type="picture-card"
          >
            <i
              class="el-icon-plus"
              :style="{ display: fileList.length ? 'none' : 'inline-block' }"
            ></i>
            <span
              :style="{ display: fileList.length ? 'inline-block' : 'none' }"
              >点击重新选择</span
            >
          </el-upload>

// 上传照片

methods:{
     async addData() {
      let condition = new FormData();
      condition.append("fileId", this.info.fileId);
      condition.append("id", this.info.id);
      condition.append("comment", this.comment);
      condition.append("files", this.fileList[0]?.raw || await this.Base64ToFile(this.fileList[0]?.url, this.fileList[0]?.name));
      uploadFile(condition)
        .then((res) => {
          if (res.data.code === 200) {
            this.$message.success("上传成功！");
            this.$emit("successHandle")
          } else {
            this.$message.error(res.data.message);
          }
        })
        .catch((error) => {
          this.$message.error({
            message: failResponse(error).message,
          });
        });
    },

// 将base64转换为file
    Base64ToFile(dataurl, fileName) {
      const arr = dataurl.split(","),
        mime = arr[0].match(/:(.*?);/)[1],
        bstr = atob(arr[1]);
      let n = bstr.length,
        u8arr = new Uint8Array(n);
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
      }
      return new File([u8arr], fileName, { type: mime });
    },

}

// 查看照片
    getData() {
      getFile({
        fileId: this.info.fileId,
      })
        .then((res) => {
          this.comment = res.data.data.comment;
          this.fileList = [{name: res.data.data.fileName, url: 'data:image/png;base64,'+this.ArrayBufferToBase64(res.data.data.files)}]
        })
        .catch((error) => {
          this.$message.error({
            message: failResponse(error).message,
          });
        });
    },

// byte数组转字符串
    ArrayBufferToBase64(buffer) {
      // 第一步：将arrayBuffer转为二进制字符串
      let binary = '';
      let bytes = new Uint8Array(buffer);
      for (let len = bytes.byteLength, i =0; i<len;i++) {
        binary += String.fromCharCode(bytes[i]);
      }
      // 将二进制字符串转为base64字符串
      return window.btoa(binary);
    },