Re: [ft-devel] Tweak CJK Blue zone parameters

[mpsuzuki]

Hi,

If further tweak is needed for CJK bluezone, the code
would be unmatured, I will disable it by default.
In fact, the original demonstration was given by 11pt
glyph of WenQuanYi-ZenHei, but your new tweak seems to
change the dist value for the glyphs smaller than 17pt
I think 17pt is unstable/temporal tuning value and not
determined deducively. It makes me afraid that the code
includes some ad-hoc parameters and they are not tested
well.

How long do you need to find stable values for the tunable
parameters? If it is difficult to estimate, I will propose
new API to manipulate the parameters by FT2 clients.

Regards,
mpsuzuki

On Mon, 09 May 2011 00:23:58 +0800
Just Fill Bugs <address@hidden> wrote:

>Now that the CJK blue zone code are in the freetype repository, further 
>tweak on the parameters can be performed.
>
>One thing that I can think of is that the threshold of best_dist0 used 
>in the af_cjk_hints_compute_blue_edges(). best_dist0 is used to 
>initialize the snap distant from edges to one of the blue zones.
>
>It's initially set to 1/40 of EM, and scaled to the rendering size. That 
>means any edge that is closer to 1/40 of the EM (1024 or something) 
>points toward a blue zone will snap to the blue zone.
>
>At smaller rendering size, we can have much less possible different 
>edges in limited space. For example, at 16 pixel, we can only have
>1/16 different edges, less than the 1/40. (more different edges when 
>considering anti-alias rendering, but that's fuzzy.)
>
>Therefore, we can force a bigger snap distance so that we can have more 
>uneven edges aligned. Especially when we deliberately merge some glyph 
>features at the smaller font size.
>
>What's the suitable snap distance will vary over fonts. I wrote a patch 
>to set the distance at 1/24 for 16px or smaller font size. Different 
>numbers can be used to experiment with all kind of fonts.
>
>More dynamic adjustment can be archived by linking the best_dist0 value 
>to the delta between filled/unfilled blue zones.
>
>