LibTiff.Net Tiff image = Tiff.Open(fileName, "r") always return null

Question

My C# application has to handle TIFF files, but LibTiff.Net always returns null by this code.

using BitMiracle.LibTiff.Classic;
...
using (Tiff image = Tiff.Open(fileName, "r"))
{
    if (image == null)
    {
        //Always return null.
    }
}

Answer 1

I finally found that I use image.RotateFlip() to rotate image. It changed EXIF (Image metadata) to png, so LibTiff returns null