C#里面用指针浏览图像的每个像素灰度值

IntPtr mbuffer = IntPtr.Zero;
unsafe
{
        GrabDlg.m_Buffers.GetAddress(out mbuffer);  //读取图像数据的句柄
        byte* aa = (byte*)mbuffer.ToPointer();          //把数据句柄转化为byte指针
        for (int i = 0; i < GrabDlg.m_Buffers.Width; i++)    //返回每个像素的灰度值
        {
               int y = Convert.ToInt32(*aa);
               aa++;
        }
}