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How undo image dithering that resulted when millions colors image converted to 256?

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2015-11-01 03:56:31 UTC (over 8 years ago)
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1

How undo image dithering that resulted when millions colors image converted to 256?

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.

Alain Daumail
2015-11-02 19:59:43 UTC (over 8 years ago)

How undo image dithering that resulted when millions colors image converted to 256?

May be you would try
- Change image scale & size to 400% to make room for smoothing - Then use a G'MIC filter
Filter/GMIC/Repair/Recursive median ( seems to work well on your sample)
Fiiter/GMIC/Repair/Smooth[Anisotropic] or [Median], [Thinbrush], [Upscale]... (are other options)
- Then reduce scale & size as needed

-----------------------------------------

Le 01/11/2015 04:56, AppStoreWannabe a crit :

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.