Re: [ft-devel] Seams with disjoint composite

[Behdad Esfahbod]

BTW, checkout DejaVuSans at 4pt.  I see all kinds of triangular artifacts.

On 06/07/2012 12:40 PM, Behdad Esfahbod wrote:
> 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?
> 
> behdad
> 
>> Of course, a much simpler (and probably even better) solution is to
>> avoid subglyphs if they touch at longer lines.
>>
>>
>>     Werner