[Freetype] Test: Native PS T1 hints vs. PS Auto-Hinter on TrueType outlines

[Vadim Plessky]

I think that one real example is better than thousand words, so I conducted 
in-depth testing of several TrueType and Type1 fonts with FT 2.0.9.
My FT 2.0.9 has Bytecode Interpreter disabled, so all this is about PS 
auto-hinter and its handling of "naked" TrueType outlines and pre-defined PS 
hints.
Screenshots go first:  
http://freetype.newmail.ru/newton-11pt-7pt.png
http://freetype.newmail.ru/newton-13pt-10pt.png
Left column - PFB (Type1, hinted manually by me)
Right column - TrueType font.

Fonts itself can be downloaded from here:
http://freetype.newmail.ru/newt55v4.pfb
http://freetype.newmail.ru/newton55.ttf

To install: copy them to font directory listed in your /etc/XftConfig file, 
and run #xftcache command after all.
Fonts should appear in font list.

Test file (KWord 1.2b1): 
http://freetype.newmail.ru/Newton_PFB-vs-Newton_TT.kwd

I'd like to notice here that outline itself is *the same* in both cases.
The real differences are font format (PS vs. TT) and hinting (PS font is 
encoded in Type1 format, with manual PS hinting)
As it's visible from screenshots, native hints demonstrate significant 
improovement over auto-hinter (for this particular "Serif" font)
Note *bold* Look'n'Feel for NewtonCTT 10pt-11pt-12pt and *normal* Look'n'Feel 
for the same outline in PFB format.
I suggest this is a bug in auto-hinter - but hopefully adding manual hints 
help :-)

Note problems with diagonal stems at 12pt sizes (PFB font):
English - V W X K M N,  Cyrillic - А У
Other minor rendering bugs:
12pt - Э Я Ш (it seems VStem3 hint doesn't work for this glyph)
ф - disappears "top" part

10pt, 9pt - Й (right vert. stem)

For peole curious wether PostScript interepreter can do better job than FT2, 
here is screenshot of GV output, running GNU GhostScript 6.52:
http://freetype.newmail.ru/newton-pfb-GS.png

If you remember, some time ago I posted testing results for Times New Roman 
(TTF), which had quite bad rendering with FT 2.0.9.
This testing shows that problem is partially in Times New Roman outlines, but 
biggest part - in auto-hinter. Newton (it's also from Times family) has 
similar problem of "boldness" at 10pt-11pt-12pt in TF format, plus some other 
glitches caused by outline shape.
So, preparing PS T1 version from Times New Roman TTF sounds a good solution 
for"typical desktop". Of course Monotype/MS will not allow to distribute it, 
but for testing purpose it's nice to have.

Hope this testing also demonstrates that PS auto-hinter (PS hinting engine)  
is quite useful, and can be applied for "real-world" tasks.
Thanks everyone!

-- 

Vadim Plessky
http://kde2.newmail.ru  (English)
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