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Types of type : the different font file formats.
Below are reviewed the following font formats :
Type 1 fonts (a.k.a. Postscript fonts)
True Types
Type 3 & Type 5 fonts
Multiple Master fonts
GX fonts
Open fonts
1. WHAT ARE TYPE 1 FONTS ?
The Type 1 fonts (a.k.a. ATM fonts) are Postscript Font. This means that they are programmed
in Postscript, a language for page description owned by Adobe System inc.
When Macintosh was created, fonts were only Bitmap. Then, with the collaboration
of Adobe, Apple launched the Postscript Printer, using the Postscript technology
(for more information, see History
of computer font). So a Postscript Font is composed of two files:
- the Bitmap file (represented as a suitcase) also known as the Screen font, that contains
the bitmaps for various point sizes, in which are the informations for their
screen restitution. Its name generally ends with the .bmap suffix. The advent
of Adobe Type Manager
(and of the True Type fonts) made the bitmap almost obsolete. For Type 1,
ATM will render a fontsize onscreen by calculating it from the closest bmap
sizes present. So you can only keep few sizes (10 for bodies and 24 for
title seems to be a fair choice : ATM will calculate quicker than with only
one size, and your system will run faster than if you load all the bmap).
- the printer font or printer
file (which icon often represent a printer or the logo of the foundry) in
which are stored the PostScript informations for the printer.
Even if you can restrict the
bitmap sizes, a type 1 font need a printer and at least one bitmap file
to work. Note that a pointsize smaller than 1/2 of the smallest bitmap cannot
be rendered onscreen (so bad for legal mentions, but who cares!). Finally,
Macs can't deal with PC type 1 Font, as they are programmed differently.
2. WHAT ARE TRUE TYPE FONTS ?
The True type fonts were developped by Apple (and Microsoft) as an alternative to the Postscript
Fonts (Type 1, 3 or Type 5), that are relying on a technology owned by another
firm (Adobe System inc), and could create a dependancy.
The first advantage of True Type Font is that they consist in a single file,
represented as a suitcase. The name of this suitcase usually ends with the
suffix .tt or with .suit. (the later one being confusing, as the Type 1
font also features suitcases-like folders).
In this single file are stored
the infos for both the printer and the screen, under the form of one file
for each style (here a regular and a bold). In each of these files are stored
all the informations for the font: the vectors ressources (considered as
a 0 size for the screen rendering), and sometime some screen ressources
(not indispensable, they improve the screen restitution).
This constitution comes from the second advantage of True Types. The screen-
rendering program (that replace Bitmap or ATM use) is included in the system
and uses the informations of the SFNT for its work. (before System 7, it
was done by True Type Init, which was to be added to the system). Technically,
True Type are using a technology known as B-Spline that is part of the QuickDraw
GX environement. For a Type 1 font, a curve is drawn using Postscript: defining
it takes two points at its extrema, and two associated tangents. A True
Type Fonts, use a third point to define the same curve, and no tangents.
So defining the same drawing of a letter takes more points, and so more
diskspace. But as True Type fonts doesn't need any Bitmap, they are often
smaller than their Type 1 counterpart. (For developer informations about
True Type and how to build them, a 400 pages book plus additionnal files
are downloadable at ftp.uu.net).
The rendering engine for True
Type is included in the System since v.7. System 6 users must have the TrueType
Init in their system (Freeware from Apple). They are said to be rendered more slowly by ATM than the
Type 1, but they are best at small pointsizes (even if bolds are sometimes
too thin).
As they are not Postscript, True Type font cannot
be vectorized in Adobe Illustrator. Another default : if the author has
placed a screeen size for the regular but none for the italic, a True Type
Font will use an obliqued version of the regular in place of the italic.
But this only affects the screen, and does not occurs once you print. And,
more important for us type addicts, True Type principles for drawing makes
them more precise.
True Type are existing in the PC world,
and have, especially there, become a real standard for vector fonts (this
is no surprise as they were developped by Microsoft...). More: PC versions
of True Type fonts are programmed the same way than for Macintosh.
So, True Types are a real alternative to Postscript Font. As long as a new format is not
issued.
3. WHAT ARE TYPE 3 & TYPE 5 FONTS ?
Type 3 and Type 5 are two alternative Postscript outline font formats. Chances are you won't ever encounter them, but, hey, ain't we curious or not?
Type 3 were an answer from 2 major forces of Desktop publishing to the domination of Adobe : Quark (that issued X-press, still the main DTP software today among professionals) and Compugraphic, a well know electronic type foundry.
At the end of the 80', Adobe was still keeping secret the encryption of its Postscript Typefaces. As a consequency, Type 1 font could not be opened by anyone else. So Quark and Compugraphic issued their own version of Postscript fonts called Type 3 fonts.
These fonts were Postscript, but not encrypted, and they offered 2 different variants : some "classic" outlines, and some others that were built as strokes. These later files were allowing very effective tonal variations, simply by varying the weight of the strokes. This can be interesting for complex decorative fonts, or for special use (when a pattern fills inside outlines for example). Just like type 1 font, Type 3 are downloadable (from the computer to the printer), but as they were not built by Adobe, the BuildChar routine is not in the printer (as for Type 1 or Type 5), but is built in the font.
Presumably to answer to that problem, Adobe then decided that its screen rendering device (Adobe Type Manager) would only deal with Type 1, and not Type 3. So, only Quark X-press offered screen rendering of Type 3. Gasp!
But, the deadly shot came soon after that : as True type was gaining popularity, being heralded by both Apple and Microsoft, Adobe finally decided to give away the encryption of its Postscript Type 1 fonts. This did not killed True type, but, added to the fact that Type 3 font were less legible on low quality printers, it made Type 3 quite useless. This is why you don't see much of them by now...
Type 5 fonts are the ROM-based Postscript font that are part of the printers. They generally includes Hand-tuned bitmaps for the most commonly used pointsizes in order to avoid the process of rasterization, and gain time (other pointsizes are classicaly calculated from the outline). For any other aspects, type 5 fonts are like any other Postscript Font, and in a way, are just a version of Type 1 fonts.
Now, please, you omnipotent online God, tell us what the hell are
Type 2 and Type 4!
4. MULTIPLE MASTER FONTS : THE SHAPE CHANGERS
Multiple Masters fonts
are a recent kind developped by Adobe. Their names generally ends up with
the .MM suffix and they requires Adobe's Font Creator, ATM 3.0 and the Multiple
Master Init. They are multidimensionnal types.
With Font
creator, you can interpolate on the fly between differents masters within
a font. For example, you design a X-light and a X-bold version of a font.
Once it is generated as a Multiple Master and loaded, Font Creator can create
any version between the two masters (on a scale in which the one is 0 and
the other 1000). And this is only a single dimensioned example!
The first Multiple Masters
Font issued by Adobe was the Myriad.MM, a two axis font. The first one goes
from Light to black, and the second one goes from Condensed to Extended.
This creates a four corner design space within which the font can evolute.
This is a really interesting
step in the concept of font and font design, but there are some constraints
(same number of points for an equivalent letter, etc..) and generating such
a font is complex, not to mention conceiving it. That's probably why few
MM fonts are avaliable for now, and scarcely in the Public Domain.
Technically, Multiple Masters can be used on any postscript printers,
as the operating postscript extension, nammed "makeblendedfont"
is included in the MM fonts. (further informations avaliable at Adobe's website).
5. WHAT ARE GX FONTS ?
GX fonts were annonced by Apple at the same time than its QuickDraw GX technology (1994). The GX fonts are either Type 1 or True type, and they are encoded on 16 bits. Their main advantage is that they can deal with ligatures, swash, etc... on the fly. To perform this, the font can contain a state machine (in fact this machine is a small computer program) that controls the substitution process. There is provision for another state machine controlling kerning as well, to get around the problems that can arise with simple pair-based kerning.
So what's the use? Much more intelligent fonts, first, and most of all, handling of complex alphabets like Japanese Kanji or Korean.
For the moment, there are few GX fonts, but they are quite promising. The only problem is that they are linked to the QuickDraw GX environement.
6. WHAT ARE OPEN TYPES ?
Developped by Adobe and Microsoft, Open types are the latest developpement
in font technology and represents an answer to the growing problems of typeface
management They are supposed to be the ultimate solutions against font troubles,
especially on the Net. As HTML was originally conceived to describe the
content (text) and not the appearance of informations, it is a very poor
language regarding to use of font.
To allow web authors to use
more fonts in their pages, Adobe and Microsoft came out with a project called
the Open type initiative, or True Type Open version 2, which is a new font format, a kind of superset of Type 1 fonts (postscript) and True
Types. Now released, this new technology is (to our knowing) completely compatible
with pre-existing fonts. They are also cross-platform as they works either on Macintosh or PC.
A lot more informations about
Open types will be avaliable at our forthcoming Open type initiative page and we'll soon have a dedicated page about them, and another about the mysterious dFonts used by Apple's Macintosh since Mac OSX.
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