Re: [Algorithms] Alpha Channel

[Pai-Hung C. <pa...@ac...>]

Thanks for the help.  Actually I am looking for a graphics package that
allow me to pre-process (e.g. color-keying) the alpha info into the bitmap,
so that I can use it directly as alpha-translucent billboard in my program.

Pai-Hung Chen

----- Original Message -----
From: gl <gl...@nt...>
To: <gda...@li...>
Sent: Saturday, August 26, 2000 2:48 PM
Subject: Re: [Algorithms] Alpha Channel


>
> Take a look at the 'D3DFrame' texture loader code (part of the SDK) - it
> does exactly that from alpha files.
>
> If you can use 16bit, choose the 5551 format if available, as 1 bit of
alpha
> is all you need.  BTW, you are really describing colour keying, but don't
> use it, as it's legacy and can cause all kinds of problems when combined
> with alpha blending (search the archives for details).
> --
> gl
>
> ----- Original Message -----
> From: "Pai-Hung Chen" <pa...@ac...>
> To: <gda...@li...>
> Sent: Saturday, August 26, 2000 9:08 PM
> Subject: [Algorithms] Alpha Channel
>
>
> > Hi,
> >
> > I want to use billboard in my program but cannot find a good way to
create
> > 32-bit bitmap with alpha channel of appropriate values.  Basically I
want
> to
> > create a bitmap of tree with leaves in various green colors (with alpha
=
> > 255) and all non-green colors transparent (alpha = 0) so that I can use
it
> > as the texture for my billboarded trees.  It would be nice if I can
> specify
> > a non-green color C and make the alpha of all the pixels of color C in
the
> > bitmap to 0.  Is there any program capable of doing that with 32-bit
> bitmap
> > with alpha channel?  This may be off-topic and you could send your
advise
> to
> > me off-line.
> >
> > Thanks in advance,
> >
> > Pai-Hung Chen
> >
> >
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> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
>
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