How to posterize JPEG?

[Tumbleweed666]

I have a couple of pictures I'd like to posterize, eg reduce to maybe between 4-16 colors only. Can this be done with iPhoto and if so how, or if not, what else could I use that's free ? (for an experiment with 2 photos buying something seems over the top) . I took a look at the iPhoto help but couldn't find anything.

[telecomm]

No, iPhoto doesn't do this. I'd use the GIMP (http://gimp.lisanet.de/Website/Overview.html).

If you're on Leopard, you'll also need to install X11 before the GIMP. You can get it here (http://xquartz.macosforge.org/trac/wiki).