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 <[email protected]>.




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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:

     -  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.




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     -  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.




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  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: [email protected]
     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



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        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






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     Person & email address to contact for further information:

        Glenn W. Parsons
        [email protected]

        James Rafferty
        [email protected]

     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.






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  [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: [email protected]


  James Rafferty
  Brooktrout Technology
  410 First Avenue
  Needham, MA  02494
  USA

  Phone: +1-781-433-9462
  Fax:   +1-781-433-9268
  EMail: [email protected]








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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.



















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