in the file gifti_io.h, just before #include , could the following lines be included:

#ifdef Darwin
#define __MACTYPES__
#define Byte unsigned char
#endif


i ran into a build problem on the mac, where adding this became necessary. (i had to do the same thing some time ago when building the MNI tools.)

zlib.h uses the keywork 'Byte', but it is not defined anywhere on the mac, hence this fix.

This is a zlib bug, so it does not seem appropriate to deal with in GIfTI.