[cairo] Sub-pixel Font Filtering in 1.10

Carl Worth cworth at cworth.org
Fri Jan 15 14:52:21 PST 2010

On Fri, 15 Jan 2010 20:56:26 +0000, Freddie Witherden <freddie at witherden.org> wrote:
> On Friday 15 January 2010 20:07:59 Carl Worth wrote:
> > As display devices improve, those pixel boundaries will become less
> > meaningful, and then I'll agree with you that the filtering should
> > ignore them.
> Interesting. All of the information I have seen (including viewing my own 
> screens under a microscope) showed there to be no perceptible gap between the 
> sub-pixels of adjacent pixels.

Yes. I didn't mean to suggest otherwise.

I merely meant that once we get pixels that are sufficiently small on
our display devices (200 ppi? 300? 600? I'm not sure) then we can stop
worrying about hinting altogether (and stop worrying about intra-pixel

But we're not there today, and just applying standard signal-processing
techniques (filter, sample, reconstruct), ignores the fact that we don't
get to create an arbitrary, continuous signal as the result. We instead
are creating a discrete signal that affords very high-frequency output,
(but only at pixel boundaries).

I see that Keith how written a reply stating exactly the point I was
trying to get across (and more). He's done that in his characteristic
style which is much more clear than what I wrote. So, I'll just let
things stand at that.

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