this.$axios.post('/fishweb/agent/downLoad',this.stringify({filename:'qrCode.jpg'}), {
 responseType: 'arraybuffer' //指定返回数据的格式为blob
 }).then((res) => {
 var src='data:image/jpg;base64,'+ btoa(new Uint8Array(res).reduce((data, byte) => data + String.fromCharCode(byte), ''));
 this.srcImg = src; //图片回显
 var link = document.createElement('a');
 link.href = src;
 link.download = "qrCode.jpg";
 link.click();
 })

axios({
  method: "get",
  url,
  params: xxx,
  responseType:"blob"
 }).then(response => {
  this.picUrl = window.URL.createObjectURL(response);
});