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RE: [ft-devel] [Patch] Autofit and stem snapping

From: Turner, David
Subject: RE: [ft-devel] [Patch] Autofit and stem snapping
Date: Wed, 21 Sep 2005 10:25:44 +0200

Hi Frédéric,

My first impression is that the problem is not related to subpixel
positioning at all. The bluriness seems to be the same in both
LCD and AA screenshots you've sent. It probably has to do with
the way the hinting and rendering algorithms are selected, maybe
even within FreeType itself.

funny that you're mentionning the ftview problems. I'm currently
hacking the sources for the demo programs. I've discovered a number
of bugs related to rendering modes and a few other things.

I'll let you know when I'm finished. In the meantime, I'd appreciate
if nobody changes the sources for the demo programs at the moment.


- David Turner
- The FreeType Project  (

> -----Message d'origine-----
> De : Frederic Crozat [mailto:address@hidden
> Envoyé : mercredi 21 septembre 2005 10:22
> À : Werner LEMBERG
> Cc : address@hidden; Turner, David
> Objet : Re: [ft-devel] [Patch] Autofit and stem snapping
> Le mercredi 21 septembre 2005 à 00:20 +0200, Werner LEMBERG a écrit :
> > > Ok, while investigating how to fix this bug in cairo, I found some
> > > problems between rendering of freetype 2.1.9 and 2.1.10 [...]
> > 
> > These problems seem to be related to subpixel positioning.  
> Which font
> > are you using?  Have you tried those settings with ftview 
> or ftstring?
> > Note that I don't use GTK, so I can't really help.
> Only the first problem is related to subpixel positioning, the second
> one is affecting also standard antialiasing.
> For my test, I'm using DejaVu (which is Bitstream Vera with additional
> non-latin1 glyphs) Sans 10 (dpi 96). I've attached the font 
> to this mail
> to ease debugging.
> I've just tried to use a little ftview (I'm not an expert 
> with it) and I
> discovered interesting things (this is with freetype2 CVS HEAD) :
> for the first bug I reported :
> -run ftview -r 96 10 DejaVuSans.ttf 
> -switching rendering mode between normal, light (notice there is no
> rendering change between light and normal), horizontal LCD RGB (with
> ugly yellow halo), horizontal LCD BGR (ugly blue hallow), vertical LCD
> RGB and vertical LCD BGR. Now, do this cycle another time and 
> notice how
> the yellow and blue halos have disappeared in horizontal LCB 
> rendering,
> as well as the rendering is now different between normal and light
> rendering.
> -btw, if I try to enable normal cache instead of sbits cache, 
> I'm unable
> to get any subpixel rendering (but it might be normal, again, I'm a
> newbie concerning Freetype2 and ftview :)
> for the second bug I reported :
> -run ftview -r 96 10 DejaVuSans.ttf 
> -switch between no antialiasing and antialising => when AA is enabled
> back, glyphs are the same as when you started ftview
> -switch between normal and sbits cache => no visible difference
> -switch to normal cache and then disable and enable back AA 
> => now, you
> don't get the same rendering as before. You can now switch between
> normal and sbits cache to see differences in rendering. 
> -- 
> Frederic Crozat <address@hidden>
> Mandriva

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