Does netpbm compile for you on Mac OS X? I do have problems compiling  
it:

gcc -pipe -c -I/Users/schwarz/pkgsrc/graphics/netpbm/work/ 
netpbm-10.32/converter/ppm/ppmtompeg/headers  -I/include -I/Users/ 
schwarz/pkgsrc/graphics/netpbm/work/netpbm-10.32/converter/ppm/ 
ppmtompeg -I. -I importinc -DNDEBUG \
     -no-cpp-precomp -I/Users/schwarz/pkg/include -I/usr/include -O3 - 
fgcse-sm -funroll-loops -fstrict-aliasing -fsched-interblock -falign- 
loops=16 -falign-jumps=16 -falign-functions=16 -falign-jumps-max- 
skip=15 -falign-loops-max-skip=15 -malign-natural -ffast-math - 
freorder-blocks -freorder-blocks-and-partition -finline-floor - 
mpowerpc-gpopt -force_cpusubtype_ALL -fstrict-aliasing -mtune=G5 - 
mcpu=G5 -mpowerpc64 -I/Users/schwarz/pkg/include -I/usr/include   -o  
frame.o frame.c
frame.c: In function 'Frame_AllocBlocks':
frame.c:643: internal compiler error: in compare_and_jump_seq, at  
loop-unswitch.c:122
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://developer.apple.com/bugreporter> for instructions.
{standard input}:757:FATAL:.abort  detected.  Assembly stopping.
gnumake[3]: *** [frame.o] Error 1
gnumake[2]: *** [ppmtompeg/all] Error 2
gnumake[1]: *** [ppm/all] Error 2
gnumake: *** [converter/all] Error 2
*** Error code 2

Stop.
bmake: stopped in /Users/schwarz/pkgsrc/graphics/netpbm


-- 
Georg Schwarz    http://home.pages.de/~schwarz/
georg.schwarz@freenet.de  +49 178 8545053