    Network Working Group                                         G. Parsons
    Request for Comments: 2302                              Northern Telecom
    Category: Standards Track                                    J. Rafferty
                                                        Human Communications
                                                                   S. Zilles
                                                         Adobe Systems, Inc.
                                                                  March 1998

                   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 (1998).  All Rights Reserved.

    Overview

       This document describes the registration of the MIME sub-type
       image/tiff.  The baseline encoding is defined by [TIFF].

    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>.

    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. 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:

    Parsons, et. al.            Standards Track                     [Page 1]

    RFC 2302                          TIFF                        March 1998

         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.

     2.1 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.

    2.2 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.

    Parsons, et. al.            Standards Track                     [Page 2]

    RFC 2302                          TIFF                        March 1998

    3. MIME Definition

    3.1 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 re-defines the
       original image/tiff definition to refer to all of the profiles and
       extensions that build on 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 3.2) to enable identification of
       a specific subset of TIFF and TIFF extensions for the encoded image
       data.

    3.2 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 using a fictional value 'foo':

                     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.

    4.  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

    Parsons, et. al.            Standards Track                     [Page 3]

    RFC 2302                          TIFF                        March 1998

       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.  New
          values should be defined in standards track RFCs and the
          values should be registered with IANA, using the
          registration form included in Appendix A.  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
          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

    Parsons, et. al.            Standards Track                     [Page 4]

    RFC 2302                          TIFF                        March 1998

          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/pdff
          iles/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
          Glenn.Parsons@Nortel.ca

          James Rafferty
          Jrafferty@worldnet.att.net

          Stephen Zilles
          szilles@adobe.com

          Intended usage: COMMON

          Change controller:  Stephen Zilles

    Parsons, et. al.            Standards Track                     [Page 5]

    RFC 2302                          TIFF                        March 1998

    5. Authors' Addresses

       Glenn W. Parsons
       Northern Telecom
       P.O. Box 3511, Station C
       Ottawa, ON  K1Y 4H7
       Canada
       Phone: +1-613-763-7582
       Fax:   +1-613-763-2697
       Email: Glenn.Parsons@Nortel.ca

       James Rafferty
       Human Communications
       12 Kevin Drive
       Danbury, CT 06811-2901
       USA
       Phone: +1-203-746-4367
       Fax:   +1-203-746-4367
       Email: Jrafferty@worldnet.att.net

       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

    6. References

       [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.
       [TIFF] Adobe Developers Association, TIFF (TM) Revision 6.0 - Final,
            June 3, 1992.
       [TPC.INT] Malamud, C. and M. Rose, "Principles of Operation for the
            TPC.INT Subdomain:  Remote Printing -- Technical Procedures",
            RFC 1528, October 1993.
       [TIFFPLUS] McIntyre, L., Zilles, S., Buckley, R., Venable, D.,
            Parsons, G., and J. Rafferty, "File Format for Internet Fax",
            RFC 2301, March 1998.
       [TIFF] Parsons, G., and J. Rafferty, "Tag Image File Format
            TIFF) -- R Profile for Facsimile, RFC 2306, March 1998.

    Parsons, et. al.            Standards Track                     [Page 6]

    RFC 2302                          TIFF                        March 1998

    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 - ("foo" 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 use
       of the new parameter should be defined here or in the referenced
       standards track RFC.)

       Person & email address to contact for further information:

       (fill in contact information)

       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.

    Parsons, et. al.            Standards Track                     [Page 7]

    RFC 2302                          TIFF                        March 1998

    Full Copyright Statement

       Copyright (C) The Internet Society (1998).  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.

    Parsons, et. al.            Standards Track                     [Page 8]