var img = res.currentTarget.dataset.url;
if(img){
  wx.getImageInfo({
    src: img,
    success: function (res) {
      console.log(res);
      wx.getSetting({
        success: (res) => {
          if (!res.authSetting['scope.writePhotosAlbum']) {
            wx.authorize({
              scope: 'scope.writePhotosAlbum',
              success:()=> {
                console.log('刚授权');
                wx.saveImageToPhotosAlbum({
                  filePath : img
                });
              },
              fail: (res) =>{
                console.log(res);
              }
            })
          }else{
            console.log('已授权');
            wx.saveImageToPhotosAlbum({
              filePath : img
            })
          }
        },
        fail: (res) =>{
          console.log(res);
        }
      })

    }
  }) ;
}

图片域名已添加downloadfile，真机调试错误，以上测试代码，问题出在哪？