Network Working Group G. Parsons
Internet Draft Nortel Networks
J. Rafferty
Brooktrout Technology
S. Zilles
Document: <draft-ietf-fax-tiff-regbis-01.txt> Adobe Systems, Inc.
Category: Informational May 3, 2000
Tag Image File Format (TIFF) - image/tiff
MIME Sub-type Registration
<draft-ietf-fax-tiff-regbis-01.txt>
Status of this Memo
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1. Abstract
This document describes the registration of the MIME sub-type
image/tiff. The baseline encoding is defined by [TIFF]. This
document refines an earlier sub-type registration in RFC 1528
[TPC.INT].
2. Conventions used in this document
The key words "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].
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3. Overview
This document describes the registration of the MIME sub-type
image/tiff. The baseline encoding is defined by [TIFF].
4. Internet Fax Working Group
This document is a product of the IETF Internet Fax Working Group.
All comments on this document should be forwarded to the email
distribution list at <ietf-fax@imc.org>.
5. TIFF Definition
TIFF (Tag Image File Format) Revision 6.0 is defined in detail by
Adobe in [TIFF]. The documentation can be obtained from Adobe at:
Adobe Developers Association
Adobe Systems Incorporated
345 Park Avenue
San Jose, CA 95110-2704
Phone: +1-408-536-6000
Fax: +1-408-537-6000
A copy of this specification can also be found in:
ftp://ftp.adobe.com/pub/adobe/devrelations/devtechnotes/pdffiles/
tiff6.pdf
While a brief scope and feature description is provided in this
section as background information, the reader is directed to the
original TIFF specification [TIFF] to obtain complete feature and
technical details.
5.1 TIFF Scope
TIFF describes image data that typically comes from scanners, frame
grabbers, and paint- and photo-retouching programs. TIFF is not a
printer language or page description language. The purpose of TIFF
is to describe and store raster image data. A primary goal of TIFF
is to provide a rich environment within which applications can
exchange image data. This richness is required to take advantage of
the varying capabilities of scanners and other imaging devices.
Though TIFF is a rich format, it can easily be used for simple
scanners and applications as well because the number of required
fields is small.
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5.2 TIFF Features
Some of the features of TIFF (from [TIFF]) are:
- TIFF is capable of describing bilevel, grayscale, palette-color,
and full-color image data in several color spaces.
- TIFF includes a number of compression schemes that allow
developers to choose the best space or time tradeoff for their
applications.
- TIFF is designed to be extensible and to evolve gracefully as new
needs arise.
- TIFF allows the inclusion of an unlimited amount of private or
special-purpose information.
6. MIME Definition
6.1 image/tiff
The image/tiff content-type was previously defined in RFC1528 as
containing TIFF 6.0 encoded image data, with specific reference made
to a subset known as TIFF Class F. This document redefines the
original image/tiff definition to refer to TIFF 6.0 [TIFF] encoded
image data, consistent with existing practice for TIFF aware Internet
applications. This definition is further enhanced by introducing the
new "application parameter" (section 6.2) to enable identification of
a specific subset of TIFF and TIFF extensions for the encoded image
data.
6.2 Application parameter
There are cases where it may be useful to identify the application
applicable to the content of an image/tiff body. Typically, this
would be used to assist the recipient in dispatching a suitable
rendering package to handle the display or processing of the image
file. As a result, an optional "application" parameter is defined for
image/tiff to identify a particular application's subset of TIFF and
TIFF extensions for the encoded image data, if it is known. No values
are defined in this document.
Example:
Content-type: image/tiff; application=foo
There is no default value for application, as the absence of the
application parameter indicates that the encoded TIFF image is
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Baseline TIFF or that it is not necessary to identify the
application. It is up to the recipient's implementation to determine
the application (if necessary) and render the image to the user.
7. IANA Registration
To: ietf-types@iana.org
Subject: Registration of Standard MIME media type image/tiff
MIME media type name: image
MIME subtype name: tiff
Required parameters: none
Optional parameters: application
There is no format specified for the value of this parameter
in addition to that specified by [MIME1]. Various
applications of TIFF may define values as required. There is
no default value for application, as the absence of the
application parameter indicates that the encoded TIFF image
is Baseline TIFF or that it is not necessary to identify the
application. It is up to the implementation to determine the
application (if necessary) and render the image to the user.
Encoding considerations: Binary or Base-64 generally preferred
Security considerations:
TIFF utilizes a structure which can store image data and
attributes of this image data. The fields defined in the TIFF
specification are of a descriptive nature and provide
information that is useful to facilitate viewing and
rendering of images by a recipient. As such, the fields
currently defined in the TIFF specification do not in
themselves create additional security risks, since the fields
are not used to induce any particular behavior by the
recipient application.
TIFF 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
TIFF specification. Indeed, the definition of fields which
would include such processing instructions is inconsistent
with the goals and spirit of the TIFF specification.
Interoperability considerations:
The ability of implementations to handle all the defined
applications (or profiles within applications) of TIFF may
not be ubiquitous. As a result, implementations may decode
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and attempt to display the encoded TIFF image data only to
determine that the image cannot be rendered. The presence of
the application parameter may aid in allowing this
determination before dispatching for rendering. However, it
should be noted that the parameter value is not intended to
convey levels of capabilities for a particular application.
Published specification:
TIFF (Tag Image File Format) is defined in:
TIFF (TM) Revision 6.0 - Final _ June 3, 1992
Adobe Developers Association
Adobe Systems Incorporated
345 Park Avenue
San Jose, CA 95110-2704
Phone: +1-408-536-6000
Fax: +1-408-537-6000
A copy of this specification can be found in:
ftp://ftp.adobe.com/pub/adobe/devrelations/devtechnotes/pdffi
les/tiff6.pdf
Applications which use this media type:
Imaging, fax, messaging and multi-media
Additional information:
Magic number(s):
II (little-endian): 49 49 42 00 hex
MM (big-endian): 4D 4D 00 42 hex
File extension(s): .TIF
Macintosh File Type Code(s): TIFF
Person & email address to contact for further information:
Glenn W. Parsons
gparsons@nortelnetworks.com
James Rafferty
jraff@brooktrout.com
Stephen Zilles
szilles@adobe.com
Intended usage: COMMON
Change controller: Stephen Zilles
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8. References
[REQ] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[MIME1] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, Innosoft, First Virtual, Nov 1996.
[MIME4] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures", RFC 2048,
Innosoft, First Virtual, Nov 1996.
[TIFF] Adobe Developers Association, TIFF (TM) Revision 6.0 - Final,
June 3, 1992.
[TPC.INT] C. Malamud, M. Rose, "Principles of Operation for the
TPC.INT Subdomain: Remote Printing -- Technical Procedures",
RFC 1528, 10/06/1993
9. Author's Addresses
Glenn W. Parsons
Nortel Networks
P.O. Box 3511, Station C
Ottawa, ON K1Y 4H7
Canada
Phone: +1-613-763-7582
Fax: +1-613-763-2697
Email: gparsons@nortelnetworks.com
James Rafferty
Brooktrout Technology
410 First Avenue
Needham, MA 02494
USA
Phone: +1-781-433-9462
Fax: +1-781-433-9268
Email: jraff@brooktrout.com
Stephen Zilles
Adobe Systems Inc.
Mailstop W14
345 Park Avenue
San Jose, CA 95110-2704
USA
Voice: +1-408-536-4766
Fax: +1-408-536-4042
Email: szilles@adobe.com
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Appendix A: IANA Registration form for new values of Application
Parameter
To: IANA@isi.edu
Subject: Registration of new values for the Application parameter
of image/tiff
MIME type name: image/tiff
Optional Parameter: Application
New Value(s): Application=foo
Description of Use:
foo - (Ofoo0 is a fictional new value used in this message as
an example, it is to be replaced with the new value being
registered. Include a short description of the use of the new
value here. This must include reference to a standards track
RFC for the complete description; the use of the value must
be defined completely enough for independent implementation.)
Security Considerations:
(Any additional security considerations that may be introduced
by useof the new parameter should be defined here or in the
referenced standards track RFC.)
Person & email address to contact for further information:
Glenn W. Parsons
gparsons@nortelnetworks.com
James Rafferty
jraff@brooktrout.com
Stephen Zilles
szilles@adobe.com
INFORMATION TO THE SUBMITTER:
The accepted registrations will be listed in the "Assigned
Numbers" series of RFCs. The information in the registration
form is freely distributable.
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