[Gs-devel] [David Turner] Re: PMingLiu and TT instructions

[Francesco Zappa Nardelli]

Hello.

I forwarded Mr. Deutsch mail to devel at freetype.org.  Following you
will find David Turner's reply.

Best regards,
-francesco

To: devel at freetype.org
Subject: Re: [Devel] ["L. Peter Deutsch" <ghost at aladdin.com>] [Gs-devel] PMingLiu 
 and TT instructions

Hello Francesco,

Francesco Zappa Nardelli a écrit :
FZ> 
FZ>  Comments for gs-devel?
FZ>
FZ> Thanks,
FZ> -francesco
 
LPD> From: "L. Peter Deutsch" <ghost at aladdin.com>
LPD> To: gs-devel at ghostscript.com
LPD> Subject: [Gs-devel] PMingLiu and TT instructions
LPD> 
LPD> I've investigated the hinting instructions for this font at some
LPD> length.  What I've found is that for the overwhelming majority of
LPD> glyphs, the freedom vector and projection vector are set to
LPD> either the X axis or the Y axis; and from examining the use of
LPD> NO_APPLE_PATENT in ttinterp.c of the Freetype2 code, it appears
LPD> that the authors of the Freetype2 TT instruction interpreter
LPD> believe(d) that the Apple patent(s) only apply when the freedom
LPD> and projection vectors are set to positions *other than* the X
LPD> and Y axis.

That's true, but I could never take the time to look for relevant
prior art.  I would be extremely surprised not to find some
however.. Note also that Apple lawyers will certainly complain one way
or the other..

There is also the problem of DELTA instructions, which are also
disabled by the macro I believe.

Normal TrueType fonts use the patented behaviour quite a lot to hint
diagonals properly, so it's not like it's going to produce reasonable
output for a lot of fonts, especially the Microsoft ones :-)

LPD> So if this is true (and this should be checked with the Freetype
LPD> group), and if Mr. Suzuki or someone else can confirm that
LPD> compiling the Freetype2 interpreter *with* the instruction
LPD> interpreter but also with NO_APPLE_PATENT defined produces
LPD> reasonable-looking output, then it appears we have a usable
LPD> approach.


probably, but I don't think we'd distribute a default build of the
library with these settings. They're better in a controlled
environment like Ghostscript where you can use custom font drivers for
specific purposes..

Regards,

- David


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