title: Open Babel can't convert from mol2 to png because Cairo library is not loaded
body: <p>I first installed Open Babel through brew. When I tried to run the command: "obabel -:"CC(=O)Cl" -opng -O mymol.png", I got this error message: " Open Babel Error  in PNG Format
    PNG2Format not found. Probably the Cairo library is not loaded." I then proceeded to use brew to uninstall Open Babel. Then, I installed Cairo with brew and then installed Open Babel with brew again. Still though, I try to create a PNG output and it gives me the same error message. I just do not know what's going on??</p>