Download libpng 1.5.1.
Extract the archive, then rename the created libpng-1.5.1 directory to
libpng-1.5.1-x86.
Extract the archive again, then rename the libpng-1.5.1 directory to
libpng-1.5.1-x64.
Extract the archive again, then rename the libpng-1.5.1 directory to
libpng-1.5.1-ppc.
Go into the libpng-1.5.1-x86 directory, then run ./configure.
Edit the Makefile.
Add " -arch i386" (without the quotes) to the end of the CFLAGS = line.
Do the same thing to the LDFLAGS = line.
Save the Makefile, then run make.
Repeat in the libpng-1.5.1-x64 directory, but use "-arch x86_64".
Repeat in the libpng-1.5.1-ppc directory, but use "-arch ppc".
Go back into the directory above all three libpng-1.5.1 directories and run the
following command:
libtool -o libpng15u.a libpng-1.5.1-x86/.libs/libpng15.a libpng-1.5.1-x64/.libs/libpng15.a libpng-1.5.1-ppc/.libs/libpng15.a
Use sudo to copy libpng15u.a into /usr/local/lib/.
