A File Format for the Exchange of Images in the Internet
RFC 1314

Document Type RFC - Historic (April 1992; No errata)
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Network Working Group                                            A. Katz
Request for Comments: 1314                                      D. Cohen
                                                              April 1992

        A File Format for the Exchange of Images in the Internet

Status of This Memo

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


   This document defines a standard file format for the exchange of
   fax-like black and white images within the Internet.  It is a product
   of the Network Fax Working Group of the Internet Engineering Task
   Force (IETF).

   The standard is:

        ** The file format should be TIFF-B with multi-page files
           supported.  Images should be encoded as one TIFF strip
           per page.

        ** Images should be compressed using MMR when possible.  Images
           may also be MH or MR compressed or uncompressed.  If MH or MR
           compression is used, scan lines should be "byte-aligned".

        ** For maximum interoperability, image resolutions should
           either be 600, 400, or 300 dpi; or else be one of the
           standard Group 3 fax resolutions (98 or 196 dpi
           vertically and 204 dpi horizontally).

   Note that this specification is self contained and an implementation
   should be possible without recourse to the TIFF references, and that
   only the specific TIFF documents cited are relevant to this
   specification.  Updates to the TIFF documents do not change this

   Experimentation with this file format specified here is encouraged.

Katz & Cohen                                                    [Page 1]
RFC 1314                 Image Exchange Format                April 1992

1.  Introduction

   The purpose of this document is to define a standard file format for
   exchange of black and white images using the Internet.  Since many
   organizations have already started to accumulate and exchange scanned
   documents it is important to reach agreement about an interchange
   file format in order to promote and facilitate the exchange and
   distribution of such documents.  These images may originate from
   scanners, software, or facsimile (fax) machines.  They may be
   manipulated by software, communicated, shared, duplicated, displayed,
   printed by laser printers, or faxed.

   This file format provides for the uniform transfer of high quality
   images at a reasonable cost and with reasonable speed whether these
   files are generated by scanners, totally by software (e.g., text-to-
   fax, bitmap-to-fax, OCR, etc), or by fax.  Also the intent of this
   document is to remain compatible with future moves to multi-level
   (i.e., gray-scale), higher resolution, or color images.  The format
   proposed here is supported by both commercially available hardware
   and commercial and public domain software for most popular platforms
   in current use.

   The file format for images is a totally separate issue from how such
   files are to be communicated.  For example, FTP or SMTP could be used
   to move an image file from one host to another, although there are
   complications in the use of SMTP as currently implemented due to file
   size and the need to move binary data.  (There is currently a
   proposal for removing these limitations from SMTP and in particular
   extending it to allow binary data.  See reference [1].)

   One major potential application of the communications format defined
   here is to allow images to be sent to fax machines using the
   Internet.  It is intended that one or more separate companion
   documents will be formulated to address the issues of standardization
   in the areas of protocols for transmitting images through the
   Internet and the issues of addressing fax machines and routing faxes.
   Just as the exchange format is separate from the transmission
   mechanism, it is also separate from how hosts store images.

   This document specifies a common exchange format; it does not require
   a host to store images in the format specified here, only to convert
   between the host's local image storage formats and the exchange
   format defined here for the purpose of exchanging images with other
   hosts across the network.

   This standard specifies the use of TIFF (Tagged Image File Format,
   see below) as a format for exchange of image files.  This is not a
   specific image encoding, but a framework for many encoding

Katz & Cohen                                                    [Page 2]
RFC 1314                 Image Exchange Format                April 1992
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