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Re: [ft] FreeType rasterization grid fitting regime?

From: David Turner
Subject: Re: [ft] FreeType rasterization grid fitting regime?
Date: Wed, 10 May 2006 10:53:43 +0200
User-agent: Thunderbird 1.5 (Windows/20051201)


Sorry to say this, but it seems you don't understand what the code in ftraster.c does, or how it relates to the rest of the font engine. Sadly, I won't be able to give you details here, since it'd be a bit long.

Have you tried running your program with the current FreeType CVS (which is about to be released as 2.2.1 in a few days) ?. It contains a much better auto-hinter for CJK fonts, and this may improve
your rendering.

Hope this helps,

- David Turner
- The FreeType Project  (

Dakai Liu a écrit :
Sorry If you have seen it on developer's mail list.

Hello all,

I am working on a rip project that uses FreeType 2.1.10 as font engine. While I render an Asian font at 6 point size at 600x600 dpi, the box size is 50x50. The font is a type1 font. FreeType produces un-even horizontal strokes. During debug, I found that a macro in ftraster.c:371

#define SCALED(x)  ( ( (x) << ras.scale_shift ) - (ras.precision_half) )

is trying to fit the points into the centre of a pixel. but some certain Y value is already at the centre of a pixel. So SCALED moved the Y value to the edge of the pixel. I guess this may contribute to the un-evenness of a horizontal stroke. So I modified it to:

#define SCALED(x)  ( (x) << ras.scale_shift )

So the whole grid fitting changed, but the output looks much better. also the serif at the top appeared. By examining the font file, at 6 point size at 600dpi, we should have 1 pixel sized serif.

I am pretty much puzzled and need some enlightment. I enclosed the font file.



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