Where is the antialiasing?

Carl Worth cworth at cworth.org
Mon Apr 30 09:44:11 PDT 2007

On Mon, 30 Apr 2007 10:16:04 +0530, "Konrad Merz" wrote:
> I'm interested where I can find the algorithm for the anti-aliasing in
> Xorg? So I don't mean the font antialaising.  For example when the
> Xclock is drawn antialiased. I hope I ask the right list.

It's inside the X server's implementation of what you get when you
call XRenderCompositeTrapezoids from the client. For an all-software
case ends up being in xserver/fb/ . Look at the fbRasterizeTrapezoid
function in fbtrap.c and then notice that the heavier lifting happens
inside various fbRasterizeEdges functions in fbedge.c.

The algorithm involves simple point sampling with a uniformly-spaced
grid of sampling points, (this is known to be a very poor choice for
configuring the sampling points).

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