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

From: Frederic Crozat
Subject: Re: [ft-devel] [Patch] Autofit and stem snapping
Date: Wed, 21 Sep 2005 10:21:47 +0200

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
-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>

Attachment: DejaVuSans.ttf
Description: application/font-ttf

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