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List:       freetype
Subject:    Re: Can FreeType be used for broadcast quality character generator ?
From:       "David Turner" <turner () Email ! ENST ! Fr>
Date:       1998-05-13 2:35:29
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Hello,

> Dear David
> 
> Thanks a lot for your valuable answer.
> Actually I'd like to integrate FreeType to my new project, character generator for \
> TV broadcast. I've some more question as followings :

> Q1. You mentioned you're working for a project for a digital television company
> by integrating FreeType.
> How do you deal with anti-aliasing problem in your project ?
> Do you accept FreeType's anti-aliasing capability as is ?
> Or improve by any means ?
> 
Actually, I perform filtering on bitmaps and/or pixmaps generated by the standard
FreeType rasterizer. I'm still experimenting with this, and I may probably integrate
the filter within the scan-line converter, but this will probably not make it into
the FreeType sources before long (there are limits, as I said..).

> Q2. You recommended to filter the bitmap to reduce  'beeeding' and 'flickering'.
> I understand it.
> At first, I had in mind to apply 16x16 lowpass filter(e.g. Gaussian) to the \
> monochrome font bitmap. But this would make the font burred in every direction, \
> i.e. all edge even straight,  curve and diagonal line. This would make the font not \
> clear look. Furthermore, the font bitmap size should be extended at least 8 pixel \
> for horizontally and vertically  to apply 16x16 filter. I mean that the boundary \
> margin should be at least half of filter window size. This solution looks strange.
> 
Sorry for an unprecise answer, but all I can say is try to think about much simple \
filters, these need to run on very low-edge hardware anyway :-)


> You said " There are several ranges of usable filters which will improve even \
> monochrome bitmaps." "This filtering process isn't a "normal" anti-aliasing (more \
> like anti-flicking)." 
> Could you explain about your filtering solution (e.g. size and coefficient) and \
> operation method in detail ? 
Some clues only :

-  very small size
-  integer operations                               ( adds + shifts )
-  not necessarily strictly linear nor symetrical ! ( depends on personal taste )

Good luck :-)

- David


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