Re: [GD-General] software for artwork

[Lionel F. <li...@mi...>]

Hello,

I have currently exactly this kind of stuff to write : something to convert
32bits pictures into 8bits with palette ARGB for the PlayStation 2. I never
really though to this question, so I though it would be easy to do (simple
octree in 4D space, or something like that).

Could you give me more details about the alpha channel multiplication ?
A quick search with Google shows me a lot of answers about the Kohonon nets.
But is there somewhere a not-too-bad free lib with source that could help me
? (in fact, I didn't give a lot of time in my schedule to do that task :))

Thank you for any advice,

Lionel.

----- Original Message -----
From: "Tom Forsyth" <to...@mu...>
To: <gam...@li...>
Sent: Wednesday, November 13, 2002 3:30 PM
Subject: RE: [GD-General] software for artwork


> Yep - we premultiply, palettise, and then un-premultiply again. Works
well.
> We've also spent quite a lot of effort finding good palettisers.
> Kohonon-network based ones are good, and weused that for the last project.
> The new one is a mad mix of various perceptual techniques and stuff (we
have
> a chap fascinated by this stuff), works in an arbitrary number of
> dimensions, but is very very slow. We plan to use the old kohonen one for
> quick previews, and then overnight crunch away at the textures with the
> slow-but-superb one.
>
> But we never found any decent out-of-the-box ones.
>
>
> Tom Forsyth - Muckyfoot bloke and Microsoft MVP.
>
> This email is the product of your deranged imagination,
> and does not in any way imply existence of the author.
>
> > -----Original Message-----
> > From: Javier Arevalo [mailto:ja...@py...]
> > Sent: 13 November 2002 09:11
> > To: gam...@li...
> > Subject: Re: [GD-General] software for artwork
> >
> >
> > Mickael Pointier <mpo...@ed...> wrote:
> >
> > > Standard quantization algorithms create artefacts, but thats not
> > > visually to disturbing when applied to color components,
> > surprisingly
> > > if you extend these algorithm to 4d, the final result is really,
> > > really crappy...
> > >
> > > I think the reasons are multiples, the first beeing that when A tend
> > > toward 0, you do not really care about the true values of RGB
> > > components (they are almost invisible at this point), so a lot of
> > > colors are used in semi translucent tints, that could have been used
> > > in nearly opaque areas.
> >
> > Yeah that's one of the places where premultiplied alpha
> > textures help...
> >
> >   Javier Arevalo
> >   Pyro Studios
>
>
>
>
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