the Hershey fonts

[Gerald I. Evenden]

>Date: Mon, 18 Oct 1993 21:49:42 +0100
>From: larss at fmi.kth.se (Lars Schylberg)
>To: grassp-list at max.cecer.army.mil
>Subject: the Hershey fonts
>
>Well I am repating this question once more since no one has answered.
>Surely someone out there must now something about these Hershey fonts.
>I guess what I am looking for is some kind of font editor that could 
>handle this font family.
>
> I wonder if someone could give me some advice how to add extra
> characters to the fonts that are used in grass.  I would like 
> the add the swedish characters a and o with dots above.  From the 
> README file in the original font directory in the source code they mention
> that it should be possible. But they don't tell how to do it.
> I would be very glad for some advice about this.
>
>Lars
>
>Lars Schylberg                       Email: larss at fmi.kth.se  
>Dept. of Geodesy and Photogrammetry    or : lasc at celsiustech.se (new)
>Royal Institute of Technology (KTH)  Tel.   +46 8 790 86 33   
>S-100 44  STOCKHOLM, SWEDEN          Fax.   +46 8 790 66 10

I suspect the reason answers are slow coming forth are due to the
complexity of the problem and I can only give some insight on the
problem as related to the MAPGEN vector graphic system which uses the
Hershey fonts.

First, it is easy to digitize new characters for the Hershey fonts.
I have done this in adding characters found on p. 24-25 of the
original Hershey documentation, but not distributed.  Others have
added characters, and I have included some of these with the
MAPGEN symbol tables.  But I do not know of any "font editor,"
probably because the system is so primative, compared to
the PostScript or TeX fonts, that nobody has bothered.
If you want to persue this, I can give you the coordinate
system layout and the layout sequence/control.

The second problem is related to usage.  A lot of the less
sophisticated character drafting systems merely have a one-to-one
mapping of the character stream entry to the dot matrix or pen
stroke actions to form that character.  Thus for and accent
grave on the character a, a new character must be used, as well
as an dot-matrix/pen-stroke table entry.  Obviously, an escaping
method can also be used, but there is no universal scheme for
this.

An alternative method for handling accents, is to have all the
accents separately formed generate the final accented character
by merging the forming actions of the character and the accent.
This is the method used by TeX and, as I recall, by troff.
But this requires supplementary table of detailed font metrics
(height, width) for each character and sophisticated software
to put the character together.  For example, the Spanish tilde
is shifted a different ammount for the lower and upper case letter n.

All of the problems associated with accented characters and fully
formed non-English roman alphabets is generally beyond anything but
sophisticated typesetting systems.  This is one reason I would like to
see PostScript as the principle (read only) output media and thus allow
us to merge the graphics of GRASS with text from some system like TeX
or LaTeX.  For my manuals, I do that now.

Incidently, the basic manual for the Hershey fonts is:

	Wolcott, N.M., Hilsenrath, J., 1976, "A contribution to
	computer typesetting techniques: tables and coodindates for
	Hershey's repertory of occidental type fonts and graphic
	symbols": Special Publication 424, National Bureau of
	Standards.

Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
voice: (508)563-6766          Postal: P.O. Box 1027
  fax: (508)457-2310                  N.Falmouth, MA 02556-1027