Re: [Linux-fbdev-devel] Alpha blending

[Sven L. <lu...@dp...>]

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 ?

> > 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)

Friendly,

Sven Luther