First, you need libjpeg installed. See How to Install Libjpeg on Mac.
Find out where libjpeg was installed
$ find /opt -name "libjpeg.dylib"
Compile and install
$ sudo CFLAGS='-arch x86_64' CPPFLAGS='-arch x86_64' \ LDFLAGS='-arch x86_64' python setup.py install
$ sudo python setup.py install