RE: [Algorithms] 256 colour palette

[Sasha P. <sa...@pr...>]

Hi everybody,

I thought maybe somebody can clarify the terms "quantization" and
"dithering", I often see them used as synonyms, while I always understood
them as quite different things. I want to know what other people think...

For me, quantization is just a replacement of one color (N-bit, e.g. 16 or
24-bit) with another color, from a smaller set (e.g. from 256 colors).
Dithering is a much more complex process, which, in addition to replacing a
pixel with nearest color, also performs _modifications_ of nearby pixels, to
give you smooth image.

For example, if you take the same 6-6-6 palette and do a quantization and,
say, error diffusion dithering, you will get different images, in first
image you will see the bad results of decreased number of colors, while the
dithered image will look much, much better.

Comments on these two terms, anyone?

Sasha.

> -----Original Message-----
> From: Tom Nettleship [mailto:to...@ar...]
> Sent: Wednesday, August 30, 2000 11:47 AM
> To: 'gda...@li...'
> Subject: RE: [Algorithms] 256 colour palette
> 
> 
> The problem you're referring to is commonly called quantization. Doing
> a web search on that might glean some results.
> 
> The two main algorithms people often use are called 'Median Cut' and
> 'Octree Quantization'. Both of these are efficient, and produce good
> results.
> 
> Get hold of a copy of Graphics Gems 1... this has a paper describing
> how to implement Octree Quantization, and also (i think) source code,
> though there may be some bugs in it.
> 
> Tom Nettleship
> 
> P.S. I turned this mail into plain text from the HTML you 
> sent... please
> don't
> send HTML posts to mailing lists; people using some mail readers can't
> decipher
> them.
> 
> > From: Matthew Davies [mailto:MD...@ac...]
> > 
> > Hi,
> > 
> > Can any of you guys give me some hints on choosing a decent 
> 256 colour
> > palette so that I can get a nice > spread of colours.  I 
> need it for a
> simple
> > 3d game so basically I need to cover common colours and 
> shades thereof.  
> >  
> > Do any of you have experience in this area.  I've had it so 
> easy with
> 24-bit graphics up until now!  :-)
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