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:

     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.

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

   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

      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

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.

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.

Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

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