on a mac?
Answers: Photoshop for sure.
They enjoy a trial on their website, merely Google it.
Should be what you have need of. If you can't digit out what to do, try pixel2life.com they enjoy lots of tutorials for you to follow and I', sure one of them will hold retouching photos.
uhh.i jus use lunapic.com.
its free.
and outstandingly flowing.
=).
Well gimp is pretty obedient plus its free, lot of relatives similar to it better than photoshop.
http://www.gimp.org/macintosh/