Re: [ft] FreeType artefact

[Dave Williss]

That brings up a good question.

It's been a while since I poked around in our code that uses FreeType, 
but as I recall, we render to grayscale bitmaps and use the gray levels 
as an alpha value to combine the requested color with the existing 
image.  I've never been 100% happy with the way it looks though.  Is 
there a recommendation on how to distribute the alpha values?  We get 
back gray values of 0 for 100% transparent to 5 for totally opaque (at 
least in FT 1.3 -- I'm stuck there due to lack of priority to upgrade).  
Linear didn't seem to work very well.  I don't know what values I'm 
using now, but it seems to make narrow strokes disappear at small sizes.

Werner LEMBERG wrote:
> > I uploaded new image, so maybe it's easier to diagnose:
> > http://66.232.119.162/img/fontbug.PNG Artefact appear only if draw
> > text over background. If white background then no problems.
> >     
>
> Aah, we are getting nearer.  It seems that the algorithm you use to
> draw on a coloured background needs some improvements.  Try to play
> with different gamma values for the anti-aliased glyphs.
>
> I can't help further since this topic is beyond my knowledge.
>
>
>     Werner
>
>
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