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

[magnus at itkonsult-olsen.com]

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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