Brian Furtaw (brian++at++sgi.com)
Wed, 22 Jan 1997 12:53:28 -0500
Someone mentioned to me that the Impact use 4D textures to map one color space
into another, but I never got the details of how to do it. That was primarily
concerning video and doing RGBA to CMYK conversions. Their is an extension that
will read textures as ABGR instead of RGBA. So I suspect what you want to do is
possible. In imagevision library this is an easy task you just switch the
channels as you copy them.
Hold on I found what I was looking for what you want is glPixelTexGenSGIX (3G)
the man page states this extension can be used as a very accurate colorspace
converter.
Brian
On Jan 22, 4:40pm, Graham Jones wrote:
> Subject: Re: Infinite Reality, Colour matrix and pfTexEnv Component
> Angus Dorbie wrote:
> >
> > On Jan 22, 10:02am, Graham Jones wrote:
> > > So I wouldn't be able to render the same object three times with
> > > three different colour matrices without downloading the texture
> > > three times (I'm trying to avoid all that data flying around the
> > > place).
> >
> > You want to use glColorTableSGI for this kind of thing.
>
> Angus,
>
> I could be barking up the wrong billboard but from a read of the manual
> and book on the colour table extension it would appear that I wouldn't
> be able to map Green to Red (for example), as I would if the colour
> matrix worked for texturing operations, but only remap, say, Green to a
> different Green.
>
> Useful as the extension may be I don't think I quite does what I need -
> please correct me if I'm wrong.
>
> Presumably if I can get the QUAD_TEXTURE_SELECT extension working for me
> and it extracts a component as an intensity texture, the extracted
> texture will render in to R, G and B.
>
> Graham.
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>-- End of excerpt from Graham Jones
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