Re: [Nautilus-list] Xft Anti-aliasing, Libart antialiasing?

[Moses Lei <mlei mtmis com>]

> No no. I was looking at the png. Use xmag and look at the second 't' in
> the Nautilus version. Due to heavy aa the stem of the 't' is almost two
> equally dark pixels, while the horizontal part that is outside the stem is
> very light, making it hard to see.

IMHO, the stem is still very apparent, and is quite readable when it's not
magnified. (Magnification tends to defeat the purpose of anti-aliasing.)
It's quite apparent that the letter is a "t," and that's what really
matters.

> > Hinted and unhinted certainly seems like a plausible reason for the
> > difference. What could be the cause of this discrepancy (between hinting
> > and no hinting)?
>
Sorry, the original intent of this comment was "why does Xft hint and
Nautilus not hint?" I'm familiar with the hinting concept; however, the
overview was helpful.

> Hints are really only needed when rendering at a low resolution (i.e. on
> a screen). When the resolution is high the grid size of the target doesn't
> affect the rendering much, since it's hard to see if one of the stems is
> one pixel wider. Normally you don't hint printed fonts at all.

Thanks for explaining this.

> Many people believe the blurred out look of AA fonts is harder on the eye,
> because it fools the brain to think the fonts are out of focus, and the
> eye keeps trying to focus in on them.

I think I'd rather look at something that looks like it looks on paper
than something that looks like it's from a computer, if it's going to be
blurred either way.

> > So when the letters are hinted, they are hinted in a way that 1) optimizes
> > them for readability as aliased, monochrome text and 2) optimizes them for
> > that specific screen resolution. But when the antialiasing is done on top
> > of these hinted letters, the net effect that one would want to generate is
> > to focus the eye as if the screen was at a *higher* resolution. Thus, the
> > eye is trying to see the letter in two resolutions at once, generating eye
> > strain.
>
> Ummm. I don't quite follow this. But it is true that hinting is normally
> done targeting aliased rendering. And it is still a matter of debate
> whether you should hint antialiased fonts, and if so, how you should do
> it.

Insert the "I'm a user, not a developer or an expert. I don't know what
I'm talking about." disclaimer here.

> My take is that we should probably let this be configurable somewhere and
> experiment with it.

Sounds good. Keith?

> Another thing of note here is that the placement of the glyphs seem to
> be slightly different. The Xft rendering seem to leave one pixel
> between each glyph, while the Nautilus rendering doesn't leave any
> room between glyphs.  Well, perhaps fractions of a pixel...
>
> Perhaps this is due to Nautilus doing subpixel placement of glyphs
> before AA and Xft only having integer glyph positions? Or they may
> just be interpreting the metrics differently.

I like the way this is done in Nautilus' rendering. It seems less
artificial.

I guess I haven't contributed anything new to this discussion, as it has
already become apparent that I prefer the unhinted antialiasing. Alex,
thanks for taking the time to actually look at the code and figure this
out.

Moses