Re: [Devel] auto-hinter - separate "rules" from lib

[Vadim Plessky]

On Monday 03 September 2001 16:59, David Turner wrote:
|   Hello Vadim,
|
|     I must say that I have a hard time understanding what you
|     mean by separating the auto-hinter *rules* :-(. I'll thus
|     describe what I've done for the up-coming Postscript hinter
|     module. I'm currently debugging this thing, and I expect to
|     release it this week or the next one by the way :-)
|

Hello David!
Under _separating "rules" from lib_ I was meaning creating/using some 
pseudo-language (a-la Keith did for Xft in XF) to better define hints for 
some characters, or character ranges.
Actually, I should not call it a *language*, as it's some kind of general 
RULES *what applies where*. Now I call it *language* just to imprrove 
understanding.
It should override *default* hints generated by auto-hinter module.
Benefit of separating *rules* from lib (FT 2.x) is that you don't need to 
recompile FT after each update to auto-ninter. :-)

For example, let me refer to Russian/Cyrillic letters "?", "?" (and their 
small variants "?", "?"). While I have seen that some auto-hinter/conversion 
programs apply VSTEM3 hint on "?", they rarely apply VSTEM3 hint on "?", 
probably because of addition of *ending part* on right part of this letter.
I understand that only native speaker (with some font design knoledge) can 
understand how really "?" and "?" should be rendered.
 
As I mentioned, after some time spent by me on manual hinting, I found that 
in most cases I just do computer work, which can be automated. And there are 
some exceptions, when I need to overwrite some defaults.

By the way, I like some ideas from TT hinting as well.
For example, instead of some sets of typical horizontal and vertical widths 
(heights) for horizontal and vertical stems, you can refer (in TrueType)  to 
exact value in table.
This is, probably, easy to implement and add to PS auto-hinter (may be, it 
canbe shared with TT module)
As rendering is done by FT, you can support such *extensions* even if Adobe 
ignores them ;-)
  
[...]
|     Basically, the hinting "intelligence" is completely hidden
|     to the font drivers. Which means that the hinter can be
|     replaced without touching the type1, cid and cff drivers
|     (once they've been modified to use the "pshinter" module
|      interfaces).

That's great! And if I understand it correctly, all fonts (PS, TT, etc.) will 
benefit from one auto-hinter.

|
|     the implementation that is to be released is Postscript
|     specific for various reasons..

Is it (still) possible to add some kind of *measurement* tools, in addition 
to *classic* PS hints?
Like: measure distance from point A to point B (dist1), and make distance 
from C to D equal to this (dist1).
I know that it's rather TrueType-ish, but it's usefull tool IMO.

Another important part missing in PS T1 is a way to keep diagonal stems of 
consistent width. I refer here to Latin X, V, W, Z; partially K, M, N, Y.
In Russian (Cyrillic) it also affects ?, ?, ?, ? (Ha, it can be different 
from Latin X), ?, ?, ?, ?, ? (Em, it also canbe different from Latin M)
So, from my usage pattern, around 11-13 glyphs will benefit from a#having 
support for diagonal hints.
Let me know what do you think about it.

After all, my question comes - how to add such *knoledge* about correct 
character/glyph rendering to auto-ninter (or *exception* module)
Adobe renderer lacks support for diagonal stems (and low-res printers had a 
lot of problems with  "?", "?", at least from my previous experience, several 
years ago)
I hope FT (auto-hinter, with extra *rules*) will beat here T1 specs and PS 
interpreters.  Correct me if I am wrong :-))
 
|
|     You could extend the module by providing a different hints
|     recording interface and changing the hinter's internals..
|     Actually, that's what is planned, but on a much larger
|     time frame :-)
|
|   Hope this helps,

Yes, thanks a lot!
Looking forward to test this version. Will it be some kind of snapshot, of FT 
2.0.5?
|
|   Regards,
|
|   - David
|
|   Vadim Plessky a ?crit :
|   > I know that David Turner was planning rewrite of FT2 auto-hinter
|   > module, but not aware of it's status.

-- 

Vadim Plessky
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