Bitmap bmp = new Bitmap(filepath);
  MemoryStream ms = new MemoryStream();
  bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
  byte[] arr = new byte[ms.Length];
  ms.Position = 0;
  ms.Read(arr, 0, (int)ms.Length);
  ms.Close();
string   pic = Convert.ToBase64String(arr);

byte[] imageBytes = Convert.FromBase64String(pic);
//读入MemoryStream对象
MemoryStream memoryStream = new MemoryStream(imageBytes, 0, imageBytes.Length);
memoryStream.Write(imageBytes, 0, imageBytes.Length);
//转成图片
Image image = Image.FromStream(memoryStream);