Re: Is there a way...?

"Paul Geisler" <paul.geisler@[EMAIL PROTECTED]
> wrote in message 
news:6cip1dF3h7nbvU3@[EMAIL PROTECTED]
>
> I think there is no operation for RGB data doing that. But there is
> GLSL, which allow you to code a little program that is executed for
> every pixel drawn ("FragmentProgram"). With this you could do any keying
> operation you like. Quite complicated way, though.
>
>
> Judie schrieb:
>> Hi,
>>
>> Lets say I have two images in memory. The first image is black and
>> white (single channel - no alpha), the second one is RGB (no alpha)
>> and has a black background.
>>
>> My goal is to draw the first BW image to the color buffer in its
>> entirety. And then to draw the second one over it making the second's
>> black background transparent without having to modify the image i.e.
>> add an alpha channel. That way the first image will show through where
>> the second image was black. If I could use a 2D Blit operation I could
>> specify that the color black was transparent. Is there an equivalent
>> type of operation in OpenGL?
>>
>> Thanks,
>>
>> Judie

A pixel shader would be simple enough.
If you are stuck with fixed pipeline, how about one multitexture with a 
GL_ADD texture environment ? Not quite right but ...
Maybe you can rig it coorectly with a tricky texture environment

jbw