PostScript fonts are outline font specifications developed by Adobe for professional digital typesetting, which uses
PostScript file format to encode font information.
Font type
Type 0
Type 0 is a "composite" font format - as described in the PostScript Language Reference Manual, 2nd Edition. A composite font
is composed of a high-level font that references multiple descendent fonts.
The OCF (Original Composite Font) format (which uses a Type 0 file structure) was Adobe's first effort to implement a format
for fonts with large character sets. Adobe then developed the CID-keyed font file format which was designed to offer better
performance and a more flexible architecture for addressing the complex Asian-language encoding and character set issues. Adobe
does not document or support OCF font format.
Type 1
Type 1 (also known as PostScript, PostScript Type 1,
PS1, T1 or Adobe Type 1) is the font format for
single-byte Roman fonts for use with Adobe Type Manager software and with PostScript printers. It can support font hinting.
It was originally a proprietary specification, but Adobe released the specification to third-party font manufacturers provided
that all Type 1 fonts adhere to it.
History
Type 1 was effectively a simplification of the PS system to store outline information only, as opposed to being a
complete language (PDF is similar in this regard). Adobe would then sell
licenses to the Type 1 technology at a very high cost, but with support for hinting. Type 3
fonts, a cheaper implementation of Type 1, allowed for all the sophistication of the PostScript language, but without the
standardized approach to hinting. Other differences further added to the confusion.
The cost of the licensing was considered very high at this time, and Adobe continued to stonewall on more attractive rates. It
was this issue that led Apple to design their own system, TrueType, around 1991. Immediately
following the announcement of TrueType, Adobe published the specification for Type 1 font format. Retail tools such as Altsys
Fontographer (on January 1995 acquired by Macromedia,
owned by FontLab since May 2005) added the ability to create Type 1 fonts. Since then, many free
Type 1 fonts have been released; for instance, the fonts used with the TeX typesetting system are
available in this format.
Technology
By using PostScript (PS) language, the glyphs are described with cubic Bezier curves (as opposed to the quadratic curves of TrueType), and thus a single set of glyphs can
be resized through simple mathematical transformations, which can then be sent to a PostScript-ready printer. Because the data of Type 1 is a description of the outline of a glyph and not a
raster image, Type 1 fonts are commonly referred to as "outline fonts". For users
wanting to preview these typefaces on an electronic display, small versions of a font need extra hints and anti-aliasing to look legible and attractive on screen.
This often came in the form of an additional bitmap font of the same typeface, optimized for
screen display. Otherwise, in order to preview the Type 1 fonts in typesetting applications, the Adobe Type Manager utility was required.
PostScript font utilities
The t1utils font utility
package by I. Lee Hetherington and Piet Tutelaers provides tools for decoding Type 1 fonts into a human-readable, and editable
format (t1disasm), reassembling them back into fonts (t1asm ), for converting between the ASCII and binary formats (t1ascii and
t1binary), and for converting from Macintosh PostScript format to Adobe PostScript font format (unpost).
Type 2
Type 2 is a character string format that offers a compact representation of the character description procedures in an outline
font file. The format is designed to be used with the Compact Font Format (CFF). The CFF/Type2 format is the basis for Type 1
OpenType fonts, and is used for embedding fonts in Acrobat 3.0 PDF files (PDF format version 1.2).
Type 3
Type 3 font (also known as, PostScript Type 3 or PS3,
T3 or Adobe Type 3) consists of glyph defined using the full PostScript language,
rather than just a subset. Because of this, a Type 3 font can do some things that Type 1 fonts cannot do, such as specify
shading, color, and fill patterns. However, it does not support hinting. Adobe Type Manager does not support Type 3 fonts.
Type 4
Type 4 is a format that was used to make fonts for printer font cartridges and for permanent storage on a printer's hard disk.
The character descriptions are expressed in the Type 1 format. Adobe does not document this proprietary format.
Type 5
Type 5 is similar to the Type 4 format but is used for fonts stored in the ROMs of a PostScript printer. It is also known as
CROM font (Compressed ROM font).
Types 9, 10, 11
Ghostscript referred them as CID font types 0, 1, and 2 respectively, documented in Adobe
supplements. Types 9, 10, 11 are CID keyed fonts for storing Types 1, 3, 42 respectively.
Type 14
Type 14, or Chameleon font format, is used to represent a large number of fonts in a small amount of storage space. The core
set of Chameleon fonts consists of one Master Font, and a set of font descriptors that specify how the Master Font is to be
adjusted to give the desired set of character shapes for a specific typeface.
Adobe does not document type 14 format.
Type 32
Type 32 is used for downloading bitmap fonts to PostScript interpreters with version number 2016 or greater. The bitmap
characters are transferred directly into the interpreter's font cache, thus saving space in the printer's memory.
Type 42
Type 42 font format is a TrueType font embedded in PostScript file format, allowing
PostScript-capable printers containing TrueType rasterizer, which was first implemented in PostScript interpreter version 2010 as
an optional feature. Support for multi-byte CJK TrueType fonts was added in version 2015. The out-of-sequence choice of the
number 42 is said to be a jesting reference to The Hitchhiker's
Guide to the Galaxy (book), where 42 is the Answer to Life,
the Universe, and Everything.
File formats
CID
CID Font (also known as CID-keyed Font, CID-based Font) is a PostScript font file format designed to address a large number of glyphs. It
was developed to support non-Roman character sets as these comprise more characters than the Roman typefaces that make up most western fonts, including Identity-H and
Identity-V fonts.
Adobe developed the CID-keyed font format to solve the problems in OCF/Type 0 fonts, for addressing the complex Asian-language
(CJK) encoding and very large character set issues.
CID-keyed font format can be used with the Type 1 font format for standard CID-keyed fonts, or
Type 2 for CID-keyed OpenType fonts.
Compact Font Format
Compact Font Format (also known as CFF font format, Type 2 font format, or CFF/Type 2 font format)
is designed to use less storage space than Type 1 fonts, by using operators with multiple arguments, various pre-defined default
values, more efficient allotment of encoding values and shared subroutines among FontSet (family of fonts). OpenType fonts can also contain glyph outlines in a CFF table.
CFF is designed to use with the Type 2 charstring format. It forms the basis for the Type 1 OpenType font format.
CFF fonts can be embedded in PDF files, starting with PDF version 1.2. Type
2 charstring font format and CID-keyed font| format can be used together for CID-keyed OpenType fonts.
A Type 1 font can be converted into CFF/Type2 format, and back to Type 1 again, without any loss of quality.
Multiple Master
-
Multiple master fonts (or MM fonts) are (or, rather, were) an extension to Adobe Systems' Type 1 PostScript
fonts, now mostly superseded by the advent of OpenType.
Multiple master fonts contain one or more "masters" — that is, original font styles — and enable a user to interpolate these font
styles along a continuous range of "axes."
OpenType
-
PostScript glyph data can be embedded in OpenType font files, but OpenType font isn't limited to use PostScript outline.
Adobe Font Metrics
Adobe Font Metrics (AFM) files contain general font information and font metrics information. AFM files are generally used directly only in Unix environments.
Printer Font ASCII
Printer Font ASCII (PFA) is an ASCII version of PFB, usually carrying ".PFA" file name
extension. It contains a font's glyph data. PFA is the form of the font used by PostScript-language interpreters, and is also the
preferred format for Type 1 fonts used in UNIX environments.
Printer Font Binary
Printer Font Binary (PFB) is a binary PostScript font format created by
Adobe, usually carrying ".PFB" file name extension. It contains a font's glyph data.
Printer Font Metric
Printer Font Metric (PFM) is a binary version of AFM, usually carrying ".PFM" file name extension. It contains font
metric information.
.INF
.inf (INFormation) files contain application-specific information in plain ASCII text, such as font menu names for
Windows and DOS-based applications. When a font is installed in Windows, the ATM Installer software takes the AFM and the INF
file as input and generates the required PFM file at installation time. The AFM and INF files are not installed in the user's
system.
.MMM
.MMM files are used for the metric data needed by multiple master fonts for the Windows environment.
.OFM
.OFM is the extension used by OS/2 for its version of binary font metrics file, starting
from version 2.1.
Windows support
Windows 95, Windows 98, Windows NT and Windows Me do not support Type 1 fonts natively.
Adobe Type Manager is needed in order to use these fonts on these operating systems.
Windows 2000, Windows XP and Windows Vista support Type 1 fonts natively through GDI
calls. The Windows Presentation Foundation introduced in
Windows Vista, which is also available for Windows XP
however drops support for Type 1 fonts, in favor of Type 2 fonts.
For Windows platforms that natively support PostScript, only binary PostScript and OpenType file formats are supported.
Windows Presentation Foundation (formerly codenamed Avalon) in
Windows Vista supports rasterizing OpenType CFF/Type 2 fonts, whereas Type 1 fonts will
still be supported in GDI, but not in GDI+.
Core Font Set
In addition of font types, PostScript specifications also defined Core Font Set, which dictates the minimum number of fonts
and character sets to be supported by each font. In PostScript 3, 136 fonts are specified, which includes the standard 35 fonts;
core fonts in Windows 95, Windows NT and Macintosh; selected fonts from Microsoft Office and the HP 110 font set.
See also
External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
