Re: [ft] Seeking answers on subpixel rendering

[Werner LEMBERG]

> > The Windows system fonts have special instructions to provide
> > optimal results for subpixel rendering. 
>
> Does this mean that, theoretically at least, the bytecodes control
> the final output of cleartype fonts down to the pixel level, and
> that fonts with complete bytecodes should come out PIXEL PERFECT on
> linux as they do on windows (give that dpi is altered to windows'
> 96dpi)?

On the pixel level, yes.  However -- and here comes the patented
ClearType stuff -- it must be combined with a sophisticated LCD filter
to produce the same output.

BTW, have a look into ftlcdfil.h and check the
FT_CONFIG_OPTION_SUBPIXEL_RENDERING option.

> Because right now they sure don't, they are extremely different.
> Will they one day be pixel verbatim with the windows renderings?

Honestly, I don't know.  Maybe David has time to fiddle around with
those extended bytecode instructions, but given the poor
documentation, it means *a lot* of trial and error while comparing
Windows renderings of fonts with the FreeType results.  I think it's
more useful to invest the time into improving the autohinter instead
(and I think David agrees with me).

> Is there some kind of wiki or documentation for what has been
> reverse engineered so far, and what needs to be done (besides the
> source itself)?

All documentation w.r.t. the extended bytecode instructions which I've
received from Microsoft has been sent to freetype-devel list.


    Werner