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From: aslam@uiucdcsp.CS.UIUC.EDU
Newsgroups: net.graphics
Subject: How are hershey fonts coded?
Message-ID: <7400003@uiucdcsp>
Date: Mon, 18-Aug-86 16:28:00 EDT
Article-I.D.: uiucdcsp.7400003
Posted: Mon Aug 18 16:28:00 1986
Date-Received: Wed, 20-Aug-86 01:48:43 EDT
Lines: 51
Nf-ID: #N:uiucdcsp:7400003:000:1978
Nf-From: uiucdcsp.CS.UIUC.EDU!aslam    Aug 18 15:28:00 1986


For some odd reason my note got chopped. Hopefully this time it makes it
through intact.

Couple of months ago, hershey fonts were posted to the net.  The
accompanying documentation in hershey.doc and README outlined what all the
files were and two example programs, hershey.f77 and hershey.c, could be
usedto display the characters in hersh.oc1, hersh.oc2 etc.  What I could not
find was an explanation of the actual vector data.  For example, character
214 is coded as:
 
  214 12PURMRR RSMSR RRURVSVSURU

The 12 indicates the number of strokes.  Each of the letter pair that
follows 12 forms an x,y coordinate.  The first character pair however
specifies the width of the character.  If the first character of a pair is a
blank then the next pair specifies a move instead of a draw.

And now the unresolved questions.

1. What is the reference point for the coordinates that have been coded
using ascii characters? For example, the second pair "RM" yields ascii
integers 82 and 77. Where is the origin for this move?

2. Why is the width of the character coded using two characters? In the
example above the characters are "PU" which gives ascii decimals 80 and 85.

3. If I want to draw a character left justified at a particular coordinate,
say x1,y1, how do I generate vectors using the width and the strokes data.

4. If I want the characters to be of a specific height and width in inches,
how do I map the hershey font data into inches?

5. Has someone developed a symbol routine based on the hershey fonts that can
draw a text string? I.e.,

  subroutine symbol( x, y, font, height, text )
  real x,y, height
  integer font
  character *(*) text

I will welcome responses that shed more light on how the hershey font data is
coded and arranged and how to use it in the setting of a routine like symbol.

Sohail Aslam
Dept. of Computer Science.
University of Illinois at Urbana-Champaign

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