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rfc:rfc3302

Network Working Group G. Parsons Request for Comments: 3302 Nortel Networks Obsoletes: 2302 J. Rafferty Category: Standards Track Brooktrout Technology

                                                        September 2002
             Tag Image File Format (TIFF) - image/tiff
                    MIME Sub-type Registration

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 This document describes the registration of the MIME sub-type
 image/tiff.  This document refines an earlier sub-type registration
 in RFC 1528.
 This document obsoletes RFC 2302.

1. 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].

2. Overview

 This document describes the registration of the MIME sub-type
 image/tiff.  The baseline encoding of TIFF (Tag Image File Format) is
 defined by [TIFF].

3. 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>.

Parsons & Rafferty Standards Track [Page 1] RFC 3302 image/tiff September 2002

4. 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:
 http://partners.adobe.com/asn/developer/PDFS/TN/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.

4.1 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.

4.2 TIFF Features

 Some of the features of TIFF (from [TIFF]) are:
  1. TIFF is capable of describing bilevel, grayscale, palette-

color, and full-color image data in several color spaces.

  1. TIFF includes a number of compression schemes that allow

developers to choose the best space or time tradeoff for their

       applications.
  1. TIFF is designed to be extensible and to evolve gracefully as

new needs arise.

Parsons & Rafferty Standards Track [Page 2] RFC 3302 image/tiff September 2002

  1. TIFF allows the inclusion of an unlimited amount of private or

special-purpose information.

5. MIME Definition

5.1 image/tiff

 The image/tiff content-type was previously defined in RFC 1528 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.

5.2 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
 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.
 New values for the image/tiff application parameter must be approved
 by the IESG prior to registration.  As a result, the publication of a
 description of parameter values in an RFC is required.
 Guidelines on writing IANA considerations for RFCs can be found in
 RFC 2434.
 An application parameter is a hint to the receiver.  It MUST NOT be
 used as a blind request to execute some arbitrary program.

Parsons & Rafferty Standards Track [Page 3] RFC 3302 image/tiff September 2002

 Instead, it should be viewed rather as an indication of what sort of
 application would be able to handle the content most appropriately.

6. 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 as hints
       to the receiver.  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:
       This media type consists of binary data.  The base64 encoding
       should be used on transports that cannot accommodate binary
       data directly.
    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 the 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

Parsons & Rafferty Standards Track [Page 4] RFC 3302 image/tiff September 2002

       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 as
       defined to date.
    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
       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:
       http://partners.adobe.com/asn/developer/pdfs/tn/TIFF6.pdf
    Applications which use this media type:
       Imaging, fax, messaging and multi-media
    Additional information:
       Magic number(s):
            II (little-endian):  49 49 2A 00 hex
            MM (big-endian):     4D 4D 00 2A hex
       File extension(s): .TIF
       Macintosh File Type Code(s): TIFF

Parsons & Rafferty Standards Track [Page 5] RFC 3302 image/tiff September 2002

    Person & email address to contact for further information:
       Glenn W. Parsons
       gparsons@nortelnetworks.com
       James Rafferty
       jraff@brooktrout.com
    Intended usage: COMMON
    Change controller: James Rafferty

6. 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 the 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
 as defined to date.

7. Changes from RFC 2302

  • Correction of magic number
  • Improvements of the security considerations
  • Change of change controller
  • Various editorials to improve clarity

8. References

8.1 Normative References

 [REQ]     Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.

Parsons & Rafferty Standards Track [Page 6] RFC 3302 image/tiff September 2002

 [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", BCP
           13, RFC 2048, November 1996.
 [TIFF]    Adobe Developers Association, TIFF (TM) Revision 6.0 -
           Final, June 3, 1992.

8.2 Non-Normative References

 [TIFFREG] Parsons, G., Rafferty, J. and S. Zilles, "Tag Image File
           Format (TIFF) -image/tiff MIME Sub-type Registration", RFC
           2302, March 1998.
 [TPC.INT] Malamud, C. and M. Rose, "Principles of Operation for the
           TPC.INT Subdomain: Remote Printing -- Technical
           Procedures", RFC 1528, October 1993.

9. Authors' 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

Parsons & Rafferty Standards Track [Page 7] RFC 3302 image/tiff September 2002

10. Full Copyright Statement

 Copyright (C) The Internet Society (2002).  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.

Parsons & Rafferty Standards Track [Page 8]

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