[Gimp-user] How undo image dithering that resulted when millions colors image converted to 256?

[AppStoreWannabe <forums gimpusers com>]

Hi everyone,

I have very old (circa 1995) computer art that is 256 colors. It is all cartoons
(you can see http://www.beachware.com/images/peter2.jpg for an example).

The original high resolution art is not available. So I want to take the 256
color computer screen art and change it to millions of colors (24 bit) art.

But the original reduction to 256 colors resulted in dithering. In that example
URL I just mentioned, you can see the alternating pixel colors used to fake the
appearance of colors not in the 256 palette.

What's the best way to take that 256 art and make the areas look smooth and not
dithered? I'm a part-time software developer, not an artist, so I'm hoping for
an easy solution.

When I first tried fixing it, I couldn't find a good way using GIMP on Mac OS X.
The Despeckle filter on a very old version of Adobe Photoshop worked okay, but
that computer is no longer available.

Thank you very much for sharing your knowledge.

-- 
AppStoreWannabe (via www.gimpusers.com/forums)