Re: [Algorithms] Alpha Channel

[gl <gl...@nt...>]

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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