🚀 go-pugleaf

clewis@ferret.ocunix.on.ca (Chris Lewis) writes:
>delahunt@adobe.com (Jim DeLaHunt) writes:
[metal type designs varied with size; phototypesetters linear]
>>PostScript technology preserved this linear scaling.  The glyph outline
>>is described in bezier curves, and the PostScript interpreter scales the
>>outline linearly to the desired size...
...
>I was under the impression that the "hints" allow the font machinery
>to do adjustments based on target point size.  From my experiments, linear
>font scaling doesn't look that great.

No, the hints are intended to help based on device resolution--they tell
the font-scaling code how to behave when the characters get small relative
to device resolution.  Examples of the hints:
	- "Flex" says "mash this curve flat if the "flex height" (roughly,
	  the deviation from a straight line) is too small relative to the
	  device pixel size.
	- "Stem width" hints say that when the size gets small enough that
	  a one-pixel difference in line width is noticeable, certain
	  widths should be made equal.
	- "Alignment zones" describe how to adjust horizontal segments so
	  those which should be at the same height actually are, when you
	  get down to where a one-pixel difference matters.
The point, again, is that they're all related to device resolution--they
kick in at 600 dpi at half the point size they do at 300.  So they don't
provide any help with the changes that should happen due to how our eyes
perceive the characters (i.e., changes based on actual size, irrespec-
tive of device resolution).

However, there are other effects that enter into apparent differences.  For
example, the rule for what pixels to turn on says "any pixel that a stroke
passes through.  This inherently darkens characters somewhat at small reso-
lutions.  (It's possible to compensate for this somewhat, but if the
correct width of a stroke is 0.5 pixel, your only choices are to make it
twice as wide as it should be or discard it and let the stroke break up.)
-- 
Dick Dunn    rcd@raven.eklektix.com   -or-   raven!rcd    Boulder, Colorado
	...Simpler is better.