Here is a more canonical patch for the Windows port:

When emacs is configured with --with-gdiplus and it is built on Mingw,
--with-jpeg, --with-png, --with-tiff and --with-gif are disabled and
those image formats are implemented using Windows' GDI+ library.

-- 
Juan José García Ripoll
http://juanjose.garciaripoll.com
http://quinfog.hbar.es