Re: [Linux-fbdev-devel] Alpha blending

[Geert U. <ge...@li...>]

On Tue, 3 Apr 2001, Sven LUTHER wrote:
> On Tue, Apr 03, 2001 at 08:17:41AM +0200, Geert Uytterhoeven wrote:
> > On Mon, 2 Apr 2001, Scott A McConnell wrote:
> > > I assume the Transp is for Alpha blending.
> > > It appears that the  API can support Alpha blending at the pixel level.
> > > 
> > > What about support at the rectangular level?
> > > 
> > > Not that they are an authority.... ;-)
> > > 
> > > http://www.pcwebopedia.com/TERM/a/alpha_channel.html
> > > 
> > > "Typically, you wouldn't define the alpha channel on a pixel-by-pixel
> > > basis, but rather per object. Different parts of the object would have
> > > different levels of transparency depending on how much you wanted the
> > > background to show through. This allows you to
> > > create rectangular objects that appear as if they are irregular in shape
> > > -- you define the rectangular edges as transparent so that the
> > > background shows through. This is especially important for animation,
> > > where the background changes from one frame to the next. "
> > 
> > That's something different. `transp' in fbdev is about transparency of the
> > screen (for a video underlay or so), not about transparency of objects to be
> > blended together on the screen.
> 
> What about anti-aliasing ?

Anti-aliasing has nothing to do with transparency on non-transparent text
consoles.

> > > Wouldn't we want an Alpha/Transp value to be passed to the three
> > > accelerated functions?
> > 
> > No, we don't want transparant text consoles :-)
> 
> Why not, it could be fun, with a big pengouin display behind ?
> 
> Alternatively, we could have a framework for userland set themable display
> engines, or something such.
> 
> (not really serious here, so don't take it so)

Sure! And use the YUV-layer on ATI RAGE 3D for a transparent image of `big
brother^H^H^H^H^H^H^Hpenguin Linus' watching you work from the right top corner
of the screen :-)

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@li...

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds