I used GIMP.
Unfortunately, my GIMP is not working right now. I upgraded to the latest Mac OSX (Leopard), and there is some glitch that requires an update to GIMP and/or X11. So, I wait.
I tried finding another program for Mac that is either free or not very expensive, and I did not have a lot of luck. The other programs just did not do all the stuff that GIMP will do.
I am sure the GIMP will work again in a few weeks.
Pasha