[ros-dev] Greenville: The story of Freetype VS the windows rasterizer---

[Filip Navara]

Just to let you know...I've already made experimental patch
yesterday and showed it to Wierd_W. It modifies only one line in
ftgrays.c.

Regards,
Filip

----- PŮVODNÍ ZPRÁVA -----
Od: magnus at itkonsult-olsen.com
Komu: "ReactOS Development List" <ros-dev at reactos.com>
Předmět: Re: [ros-dev] Greenville: The story of Freetype VS the
Datum: 19.11.2004 - 10:28:32

> Hi
> I am reading the freetype doc. you can change it from 256
> shades of grey to 16 shades of grey. That meain the hole
> freetype need to be recomping
> 
> in some where in \freetype\include\freetype\config\ you got
> follow files
> ftoption.h and ftmodule.h
> 
> that controll the hole setting for freetype.
> I am not a expert on freetype. I maby complete wrong, but
> I think we can change the T1_MAX_SUBRS_CALLS  value in
ftoption.h > to 4 instead for 16
> 
> 
> Look at all setting there if it some thing I miss.
> Magnus (GreatLord)
> 
> Citerar Wierd Wierd <wierd_w at yahoo.com>:
> 
> > Hey everybody-
> >
> > I seem to be consistantly running into troubles with
> > Freetype and Greenville.  I suspect the problem stems
> > from Freetype trying to render the glyph with too many
> > shades of grey, and I *SERIOUSLY NEED* somebody to fix
> > it.
> >
> > Here is a more technical view of the situation, and
> > the problem:
> >
> >
> > The TrueType hinting system allows each pixel to be
> > subdivided into sub-units. There are 81 subunits per
> > pixel, in a 9x9 grid, with the center being the origin
> > point.  So, it looks something like this:
> >
> > 87654321012345678
> > 7XXXXXXXXXXXXXXXX
> > 6XXXXXXXXXXXXXXXX
> > 5XXXXXXXXXXXXXXXX
> > 4XXXXXXXXXXXXXXXX
> > 3XXXXXXXXXXXXXXXX
> > 2XXXXXXXXXXXXXXXX
> > 1XXXXXXXXXXXXXXXX
> > 0XXXXXXXXXXXXXXXX
> > 1XXXXXXXXXXXXXXXX
> > 2XXXXXXXXXXXXXXXX
> > 3XXXXXXXXXXXXXXXX
> > 4XXXXXXXXXXXXXXXX
> > 5XXXXXXXXXXXXXXXX
> > 6XXXXXXXXXXXXXXXX
> > 7XXXXXXXXXXXXXXXX
> > 8XXXXXXXXXXXXXXXX
> >
> > That represents the total number of subunits, and
> > their coordinate placements within 1 pixel.
> >
> > The windows rasterizer determines the 'shade' the
> > pixel will get, based on % of coverage this pixel gets
> > from the outline, as does freetype.  The problem shows
> > up, because The windows type rasterizer only renders
> > 16 shades, including Black and White, while the
> > Freetype one renders 256 shades.
> >
> > There are only 81 units, however.
> >
> > What does this mean? It means that under freetype as
> > it currently stands, if even *ONE* pixel subunit is
> > covered by an outline, it will render as a shade of
> > grey--- While the exact same pixel, with the windows
> > rasterizer, will render as 'white' instead.
> >
> > This is because "white" is 1/256th coverage, and there
> > are only 81 subunits-- Essentially meaning that in
> > order to get 'white' out of freetype, the pixel cannot
> > be touched *AT ALL* by the glyph outline.
> >
> > On the windows rasterizer, there are only 16 shades of
> > grey, so up to 1/16th of the area can be covered, and
> > still rendered as 'white'-- or 5 subunits covered.
> >
> > This is why the windows rasterizer produces crisper
> > images than Freetype.
> >
> > I don't know how to fix this behavior in Freetype, and
> > *SERIOUSLY* need said behavior changed, As soon as
> > possible.
> >
> > Thank you.
> >
> >
> >
> >
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> >
> >
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> 
> 
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