前端处理后端返回的图片乱码

this.$axios.get('api',{responseType: 'arraybuffer'})
.then(res=>{
    this.formData.imgUrl =  'data:image/png;base64,' + btoa(
    new Uint8Array(res.data).reduce((data, byte) => data + String.fromCharCode(byte), ''))
})