Using TrueType fonts (was: AFM files)

[Reimer Behrends]

On 25 Jul, Michael Piotrowski wrote:
[...]
>> It should be noted here that Type 42 fonts are not supported by some
>> devices (they are TrueType fonts embedded in a PostScript dictionary
>> and still require the device to have a TrueType rasterizer; no problem
>> if PostScript is only used as an intermediary stage for printing or
>> for PDF conversion, but it will not be portable). Of course, conversion
>> to Type 1 fonts, while portable, has its own set of problems ...
> 
> This is correct.  For printing or distilling, use Type 42 if possible;
> most Level 2 interpreters contain a TrueType rasterizer, I think.

Yes. However, even they may be limited. The big problem is that TrueType
hinting [1] is patented, and as a result, Ghostscript in particular does
not include code to interpret TrueType hints, even though it will
properly rasterize TrueType fonts in all other respects. (Neither does
the Freetype library interpret hints, by the way -- as I understand it,
they are using an autohinter). As a result, printing or display quality
at low resolutions is likely to suffer in such a situation.

> Unless you're using free fonts, distributing PostScript files with
> embedded fonts is typically not covered by the font license, but in
> most cases, PDF is a more suitable format for distribution anyway.

Well, only recently URW donated a number of TrueType fonts (among them
an Optima and a Garamond) to the GhostPCL distribution under the AFPL
license, so some free TrueType fonts of good quality _are_ available.

                        Reimer Behrends

[1] Hinting refers to helping a font rasterizer understand how to
display outline fonts at low resolutions; for example, at screen
resolutions you might end up with the left stem of an "H" being two
pixels wide, and the right stem only one pixel, due to rounding. Hinting
avoids this and similar effects. Unfortunately, Type 1 and TrueType
hinting schemes are totally different [2] from each other, so when you
convert from one type to the other, you usually lose hinting information
entirely. However, some converters, such as ttf2pt1, will try to
automatically determine hinting for the resulting Type 1 font from its
outline definition.

[2] TrueType hinting is theoretically much more powerful than Type 1
hinting, allowing you to describe how the outline should be fitted to
the pixel grid in extreme detail; however, properly hinting a TrueType
font can take several man-months of work [3], which is why there aren't
that many well-hinted TrueType fonts, and hardly any that are free (most
free TrueType fonts on the net are totally unhinted). Microsoft's core
fonts are examples of well-hinted TrueType fonts, and are almost
unrivaled at screen resolutions, especially Verdana. Conversely, with
Type 1 fonts, hinting more or less consists of describing a number of
geometric attributes of the font and individual characters and can be
largely automated (as done in ttf2pt1, and available in most font
editors). As a result, unhinted TrueType fonts can actually improve by
being converted to Type 1, while well-hinted TrueType fonts will likely
lose quality.

[3] http://www.will-harris.com/msfont-hint.htm