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Re: [ft-devel] Seams with disjoint composite

From: Behdad Esfahbod
Subject: Re: [ft-devel] Seams with disjoint composite
Date: Thu, 07 Jun 2012 12:40:36 -0400
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv: Gecko/20120306 Thunderbird/3.1.20

On 06/05/2012 01:56 AM, Werner LEMBERG wrote:
>> I was playing with Unicode box characters, and noticed that DejaVu
>> Sans creates the glyph for ▟ out of three quadrant boxes.  At
>> different sizes I can see very noticeable seams where the sub-glyphs
>> meet.  I thought FreeType would handle these cases better, but seems
>> like I'm wrong.  Any ideas?  Does FreeType combine all contours
>> together and rasterize them in one pass, or raster them separately
>> and combine?
> They are rasterized in a single pass.  However, the DejaVu font
> doesn't contain the necessary bytecode to properly handle the rounding
> issues which inevitably happen if subglyphs are combined -- in ftview,
> press key `f' to force autohinting, and you won't see seams.  I've
> just confirmed that exactly the same issue is present with the Windows
> rasterizer, so it's not a FreeType problem.

Thanks Werner for looking into this!  Great time for asking then: are subglyph
positions rounded as part of the hinting process?


> Of course, a much simpler (and probably even better) solution is to
> avoid subglyphs if they touch at longer lines.
>     Werner

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