Re: [ft-devel] drop-out control

[David Turner]

Hi Werner,

On Wed, 30 May 2007 07:19:50 +0200 (CEST), "Werner LEMBERG" <address@hidden> 
said:
> 
> 
> Almost four years ago I've written about this topic, but haven't
> received an answer:
> 
> 1. The argument of both the SCANTYPE amd SCANCTRL instructions (in
>    ttinterp.c) are parsed but never used.
> 
> 2. ftraster.c apparently supports TrueType drop-out control modes 1,
>    2, 4, and 5, but it doesn't support mode 0.  This looks very
>    strange.  Maybe this problem has never shown up because the mode is
>    always set to 2 (which is strange also).
> 
>    Are ftraster's drop-out control modes the ones described in the
>    TrueType specification?
> 
> 3. As Top Bishop noted five years ago, FT_OUTLINE_IGNORE_DROPOUTS (in
>    ftimage.h) is not implemented.
> 
> Now that the rasterizer behaves more or less identical to the
> implementation of Microsoft, I think it would be a good idea to close
> this last gap.
> 
> David, can you shed some light on it?
> 

Sorry, I though I had already answered to this. The reason why the drop-out
mode is fixed to 2, is simply because it's the only way to get decent rendering
with most TrueType fonts. Any other mode will create some ugly artefacts. At 
least
that was the case last time I tried it, and I don't think this changed at all.

so, either the Windows/Apple rasterizer don't follow the spec to the letter, or
there is something here that is either fundamentally not understood, or not
documented. Which one is which is left as an exercise to the reader.

on the other hand, FT_OUTLINE_IGNORE_DROPOUTS should be implemented, I'll take
a look at it

Regards,

- David

> 
>     Werner
> 
> 
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