arg@huxley.UUCP (Adam R. Grossman) (02/09/91)
leslie@book.dle.dg.com (Leslie French) asks:
Does the direction of a hint make a difference, i.e. is there any
difference between (say)
150 -10 hstem and 140 10 hstem
if so, what? I've seen both 'positive' and 'negative' hints generated
for a single character, and I'm curious as to whether or not there's a
reason behind it.
First, you must understand that Type 1 hinting is declarative by nature
which means, as the Black Book ("Type 1 Font Format") points out, the "hint
system depends on an intelligent rasterizing algorithm to render the
character outlines... [and that c]onsequently the appearance of font
characters created with declarative hints will... [change] as hint
handling algorithms [change]." (p. 36)
Therefore, the answer to your question is "it depends on which interpretter
you are using" because different implementations will, by design, interpret
the hints differently.
However, two possible differences might be: (1) only part of the stem might
lie in a BlueValue zone and perhaps the zone snapping is activated only
when the stem starts/ends in the zone, or (2) since the "from" end may be
anchored before the "to" end (e.g., "from 140 to 150" vs. "from 150 to
140"), the "from" end is likely to have a more accurate placement while the
"to" end is likely to have a less accurate placement.
--
Adam Grossman
arg@bitstream.comamanda@visix.com (Amanda Walker) (02/09/91)
In article <LESLIE.91Feb8175404@book.dle.dg.com> leslie@book.dle.dg.com (Leslie French) writes: >Does the direction of a hint make a difference, i.e. is there any >difference between (say) > 150 -10 hstem >and > 140 10 hstem >if so, what? I'm still a little fuzzy on some of the details of Adobe's hinting, but my guess would be that the first argument tells the rasterizer which edge to round in absolute device space (the other is then adjusted relative to it, depending on the stem width). Just a guess, -- Amanda Walker amanda@visix.com Visix Software Inc. ...!uunet!visix!amanda -- "Furious activity is no substitute for understanding." --H. H. Williams
leslie@book.dle.dg.com (Leslie French) (02/09/91)
Does the direction of a hint make a difference, i.e. is there any
difference between (say)
150 -10 hstem
and
140 10 hstem
if so, what?
I've seen both 'positive' and 'negative' hints generated for a single
character, and I'm curious as to whether or not there's a reason
behind it.
Leslie.
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Dr L.J. French tel: +(44) 223 67600
Data General
European Development Laboratory fax: +(44) 223 65020
Betjeman House
104 Hills Road tlx: 818260 DGDLE G
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England CB2 1LQ email: leslie@bigben.dle.dg.comorthlieb@adobe.COM (Carl Orthlieb) (02/14/91)
Talked to our font guru, Terry O'Donnell... leslie@book.dle.dg.com (Leslie French) asked: > Does the direction of a hint make a difference, i.e. is there any > difference between (say) > > 150 -10 hstem and 140 10 hstem The simple answer is that it doesn't matter which way the stem zone values are declared - either of these methods will give the same result. In the case of horizontal stems, for example - the order does not determine which side of the stem is "anchored". The critical case is where these hint zones lie in alignment zones declared in the BlueValues array - such as those for the cap height, x-height, etc. In this case, alignment is controlled by a combination of where the character extremity falls in the alignment zone - and the values of other hint operators which control overshoots - namely BlueScale and BlueShift. Carl 8-)