Portable Font Resource (PFR) - application/font-tdpfr MIME Sub-type Registration
Registers the MIME type for Portable Font Resource files.
Collins, J., "Portable Font Resource (PFR) - application/font-tdpfr MIME Sub-type Registration", RFC 3073, DOI 10.17487/RFC3073, March 2001, <https://www.rfc-editor.org/info/rfc3073>.
@misc{rfc3073,
series = {Request for Comments},
number = 3073,
howpublished = {RFC 3073},
publisher = {RFC Editor},
doi = {10.17487/RFC3073},
url = {https://www.rfc-editor.org/info/rfc3073},
author = {J. Collins},
title = {{Portable Font Resource (PFR) - application/font-tdpfr MIME Sub-type Registration}},
pagetotal = 6,
year = 2001,
month = mar,
} RFC text
Contents
Network Working Group J. Collins
Request for Comments: 3073 Bitstream Inc.
Category: Informational March 2001
Portable Font Resource (PFR) - application/font-tdpfr
MIME Sub-type Registration
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document describes the registration of the Multipurpose Internet
Mail Extensions (MIME) sub-type application/font-tdpfr. The encoding
is defined by the PFR Specification.
A Portable Font Resource (PFR) contains a set of glyph shapes. Each
glyph shape is associated with a character code. The PFR format is
designed to be both compact and platform-independent. It is intended
to facilitate accurate rendering of fonts in all environments whether
or not they have the required fonts already installed.
1. Conventions used in this document
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [REQ].
2. Overview
This document describes the registration of the MIME sub-type
application/font-tdpfr. The encoding is defined by [PFR].
3. PFR Definition
PFR (Portable Font Resource) is defined by Bitstream Inc. in [PFR].
The documentation can be obtained from Bitstream at:
Bitstream Inc.
215 First Street
Cambridge MA 02142 U.S.A.
Phone: +1 617 497 6222
Fax: +1 617 868 0784
A copy of this specification can also be found at:
http://www.bitstream.com/pfrspec/index.html
While a brief scope and feature description is provided in this
section as background information, the reader is directed to the
original PFR specification [PFR] to obtain complete feature and
technical details.
3.1 PFR Scope
A PFR contains a set of glyph shapes. Each glyph shape is associated
with a character code. The PFR format is designed to be both compact
and platform-independent. It is intended to facilitate accurate
rendering of fonts in environments whether or not they have the
required fonts already installed.
The glyph shape definitions in a PFR are resolution-independent.
This allows glyph definitions to be displayed or printed on devices
with a wide variety of resolutions. It also allows glyphs to be
rendered at any size.
3.2 PFR Features
Some of the features of the PFR format are:
- Compact representation of glyph shapes
- Independent of byte order and operating system
- Independent of output device resolution
- Fully scalable to any glyph size
- Optional inclusion of bitmap glyph images
- Adopted as the font standard by DAVIC, DVB, and DTG
4. Comments
This document is submitted by J. Collins, Bitstream Inc. All
comments should be directed to <jcollins@bitstream.com>.
5. MIME Definition
The PFR media type has been previously registered with IANA as
application/vnd.truedoc. In view of its subsequent widespread
adoption as a standard font format by multiple standards bodies who
have relationships with the Internet community, Bitstream has been
asked to re-register this media type within the IETF tree.
6. IANA Registration
To: ietf-types@iana.org
Subject: Registration of Standard MIME Media type
application/font-tdpfr
MIME media type name: application
MIME subtype name: font-tdpfr
Required parameters: none
Optional parameters: none
Encoding considerations: Binary or base 64 required
Security considerations:
PFR uses a structure that can store glyph image data and encoding
arrays. The fields defined in the PFR specification are of a
descriptive nature and provide information that is useful to
facilitate viewing and rendering of glyph images by a recipient.
As such, the fields currently defined in the PFR specification do
not in themselves create additional security risks, since the
fields are not used to induce any particular behavior by the
recipient application.
PFR has an extensible structure, so that it is theoretically
possible that fields could be defined in the future which could be
used to induce particular actions on the part of the recipient,
thus presenting additional security risks, but this type of
capability is not supported in the referenced PFR specification.
Indeed, the definition of fields that would include such
processing instructions is inconsistent with the goals and spirit
of the PFR specification.
Interoperability considerations: none
Published specification:
The specification for this content type is available on request
from:
Bitstream Inc.
215 First Street
Cambridge MA 02142 U.S.A.
Phone: +1 617 497 6222
Fax: +1 617 868 0784
A copy of this specification can also be found at:
http://www.bitstream.com/pfrspec/index.html
Applications which use this media type:
Netscape Communicator, Bitstream WebFont Maker, Hexmac Typograph
Additional information: None
Magic number(s): 50 46 52 30 hex
File extension(s): PFR
Macintosh File Type Code(s): Creator: 'b$pw' Type: 'PFR '
Person to contact for further information:
"John Collins" <jcollins@bitstream.com>
Intended usage: common
Author/Change controller:
"John Collins" <jcollins@bitstream.com>
7. References
[REQ] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[MIME1] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[MIME4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures", RFC
2048, November 1996.
[PFR] Bitstream Inc. "PFR Specification",
http://www.bitstream.com/pfrspec/index.html
8. Author's Address
John Collins
Bitstream Inc.
215 First Street
Cambridge, MA 02142
Phone: +1 617 520 8401
Fax: +1 617 868 0784
EMail: jcollins@bitstream.com
9. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
AI ELI5
On this page
§1Why Register a MIME Type
When software receives a file over email or the web, it needs to know what kind of file it is in order to open it correctly. The MIME type (Multipurpose Internet Mail Extensions) is the standard label that tells a computer what a file contains.
The Portable Font Resource (PFR) is a font format created by Bitstream Inc. Before this RFC, PFR files had an older, proprietary MIME type. This document registers the official, standardized MIME type application/font-tdpfr with IANA (the Internet Assigned Numbers Authority), making it the authoritative label for PFR files on the Internet.
When you get a file, your computer looks at the label to know what to do with it. This document creates an official label for PFR font files.
§2What PFR Is
A PFR file is a compact, scalable font. It contains the shapes (glyphs) for the letters and symbols of a typeface, with each glyph linked to a character code. Because PFR glyphs are defined at high resolution independent of any specific output device, they can be displayed or printed at any size without loss of quality.
PFR is platform-independent (works on any operating system), supports optional bitmap images of glyphs alongside the scalable outlines, and is designed to be compact for efficient transmission. It was adopted as a standard font format by DAVIC (Digital Audio-Visual Council), DVB (Digital Video Broadcasting), and DTG (Digital Terrestrial Television Group), giving it industry backing beyond email.
PFR is a font file that can scale to any size without getting blurry and works on any computer.
§3The MIME Type Registration
The registered media type is application/font-tdpfr. The registration specifies that PFR files are binary data (not text) and may need to be base64-encoded for safe transmission in email. The magic number (file signature) for PFR files is the four bytes 50 46 52 30 in hexadecimal, which is readable as "PFR0" in ASCII.
The file extension is .pfr, and the Macintosh creator code is 'b$pw' with the type 'PFR '. The IANA registration notes that PFR is intended for common (widespread) use and lists example applications that support it: Netscape Communicator, Bitstream WebFont Maker, and Hexmac Typograph.
The official name is application/font-tdpfr, and PFR files start with the bytes PFR0 so computers can spot them.
§4Security and Interoperability
PFR has an extensible structure that allows future enhancements. The RFC notes that the current PFR specification includes only descriptive fields (metadata) that do not trigger special behavior in receiving software, so the current format poses no additional security risks beyond those of rendering fonts in general.
However, the RFC acknowledges that future extensions to PFR could theoretically introduce fields that modify application behavior. The document emphasizes that any such capability would be inconsistent with the goals of the PFR specification and is not supported in the current version. The registration identifies no known interoperability issues.
Font files can be extended in the future, but the current PFR format is safe. Computers just read the glyph shapes; there is nothing that makes them do unexpected things.