Okay, I understand.... My problem is that libTIFF can be used two ways.... you can open TIFF image files the recommended way - using TIFFOpen() - or you can open them with open() / fopen() etc and then manipulate the files by supplying the relevant file handle. The *nix and Apple interfaces utilise POSIX style file handles but for some bizarre reason, the Win32 interface uses WinOS handles - even though POSIX style handles would have worked perfectly well..! I've raised the issue with the libTIFF maintainers but it would be nice to find some elegant solution in the meantime.