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rfc:rfc2306

Network Working Group G. Parsons Request for Comments: 2306 Northern Telecom Category: Informational J. Rafferty

                                                 Human Communications
                                                           March 1998
       Tag Image File Format (TIFF) - F Profile for Facsimile

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

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

Overview

 This document describes in detail the definition of TIFF-F that is
 used to store facsimile images.  The TIFF-F encoding has been
 folklore with no standard reference definition before this document.

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 references the Tag Image File Format (TIFF) to define
 the F profile of TIFF for facsimile (TIFF-F) as a file format that
 may be used for the storage and interchange of facsimile images.

2. TIFF Definition

 TIFF (Tag Image File Format) Revision 6.0 is defined in detail within
 [TIFF].
 A brief review of concepts used in TIFF is included in this document
 as background information, but the reader is directed to the original
 TIFF specification [TIFF] to obtain specific technical details.

Parsons & Rafferty Informational [Page 1] RFC 2306 TIFF-F Profile March 1998

2.1 Baseline TIFF and Applications

 TIFF provides a method to describe and store raster image data.  A
 primary goal of TIFF is to provide a rich environment within which
 implementations can exchange image data.  [TIFF] characterizes
 Baseline TIFF as being the core of TIFF, the essentials that all
 mainstream TIFF developers should support in their products.
 Applications of TIFF are defined by using Baseline TIFF as a starting
 point and then defining "extensions" to TIFF that are used for the
 specific "application", as well as specifying any other differences
 from Baseline TIFF.

3. TIFF-F Definition

3.1 Introduction

 Though it has been in common usage for many years, TIFF-F has
 previously never been documented in the form of a standard.  An
 informal TIFF-F document was originally created by a small group of
 fax experts led by Joe Campbell.  The existence of TIFF-F is noted in
 [TIFF] but it is not defined.  This document defines the F
 application of [TIFF]. For ease of reference, the term TIFF-F will be
 used throughout this document as a shorthand for "F Profile of TIFF
 for Facsimile".  TIFF-F files are intended for use with the
 image/tiff MIME media content-type which includes support for the
 "application" parameter (e.g., application=faxbw).
 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 [REQ].

3.1.1 TIFF-F Historical Background

 Up until TIFF 6.0, TIFF supported various "Classes" which defined the
 use of TIFF for various applications. Classes were used to support
 specific applications and in this spirit, TIFF-F has been known
 historically as "TIFF Class F".  Previous informal TIFF-F documents
 used the "Class F" terminology.
 As of TIFF 6.0 [TIFF], the TIFF Class concept has been eliminated in
 favor of the concept of Baseline TIFF.  Therefore, this document
 updates the definition of TIFF-F as the F profile of TIFF for
 facsimile, by using Baseline TIFF as defined in [TIFF] as the
 starting point and then defining the differences from Baseline TIFF
 which apply for TIFF-F.   In almost all cases, the resulting
 definition of TIFF-F fields and values remains consistent with those
 used historically in earlier definitions of TIFF Class F.  Where some

Parsons & Rafferty Informational [Page 2] RFC 2306 TIFF-F Profile March 1998

 of the values for fields have been updated to provide more precise
 conformance with the ITU-T [T.4] and [T.30] fax recommendations,
 these differences are noted.

3.1.2 Overview

 The intent of this specification is to document:
 1)  The fields and values which are applicable for this F profile
     of TIFF for facsimile.
 2)  A minimum set of TIFF-F fields and values which should be able
     to interwork with virtually all historic TIFF-F readers.
 3)  A broader range of values for the traditional TIFF-F fields
     that will provide support for the most widely used facsimile
     compressions, page sizes and resolutions, consistent with the
     ITU-T [T.4] and [T.30] recommendations.
 The structure of the TIFF-F definition will be as follows.  A brief
 review of the structure of TIFF files and practical guidelines for
 the writing and reading of multi-page TIFF-F files is provided in
 sections 3.1.3 and 3.1.4.
 A review of TIFF-F fields follows.  Section 3.2 reviews the fields
 from Baseline TIFF that are applicable for black and white (bi-
 level) images and are also used by TIFF-F.
 Section 3.3 reviews the other required TIFF-F fields. Several fields
 that are specific extensions for  TIFF-F  are reviewed in section
 3.4.  There are also fields that may be helpful, but are not
 required.  These recommended fields are listed in the section 3.5.
 Section 3.6 defines the requirements for the minimum subset of TIFF-F
 fields and values to maximize interoperability.  Several technical
 topics, including implementation issues and warnings are discussed in
 subsequent sections.  Finally, section 3.9 introduces the TIFF-F
 Reader and Writer.  A table of the required and recommended fields
 for a TIFF-F Reader is provided, along with details on the permitted
 set of values.

3.1.3 Structure of TIFF Files

 The structure of TIFF files is specified within [TIFF].  In this
 section, a short summary of the TIFF structure is included for the
 informational purposes.   In addition, some practical guidelines for
 the use of this structure in reading and writing TIFF-F files are
 addressed in the following section 3.1.4.  The structure for writing
 "minimum subset" TIFF-F files is defined in section 3.6.2.

Parsons & Rafferty Informational [Page 3] RFC 2306 TIFF-F Profile March 1998

 A TIFF file begins with an 8-byte image file header that defines the
 byte order used within a file (see section 3.9.1), includes a magic
 number sequence that identifies the content as a TIFF file, and then
 uses an offset to point to the first Image File Directory (IFD).  An
 IFD is a sequence of tagged fields, sorted in ascending order (by tag
 value), that contains attributes of an image and pointers to the
 image data.   TIFF fields (also called entries) contain a tag, its
 type (e.g. short, long, rational, etc.), a count (which indicates the
 number of values/offsets) and a value/offset.  However, the actual
 value for the field will only be present if it fits into 4 bytes;
 otherwise, an offset will be used to point to the location of the
 data associated with the field.  In turn, this offset may itself be
 used to point to an array of offsets.
 For the case of facsimile data, many documents consist of a series of
 multiple pages.   Within TIFF, these may be represented using more
 than one IFD within the TIFF file.   Each IFD defines a subfile whose
 type is given in the NewSubfileType field.  For the case of facsimile
 data that is placed in a TIFF-F file, each facsimile page in a
 multi-page document has its own IFD.   For bi- level facsimile files,
 multiple IFDs are organized as a linked list, with the last entry in
 each IFD pointing to the next IFD (the pointer in the last IFD is 0).
 (There is also another technique for organizing multiple IFDs as a
 tree, that uses the SubIFDs field, but this technique is not
 applicable for TIFF-F images.)  Within each IFD, the location of the
 related image data is defined by using fields that are associated
 with strips.  These fields identify the size of strips (in rows), the
 number of bytes per strip after compression and a strip offset, which
 is used to point to the actual location of the image strip.
 TIFF has a very flexible file structure, but the use of some
 practical guidelines for implementors when writing  multi-page TIFF-
 F files can produce TIFF structures which are easier for readers to
 process.   This is especially for implementations in environments
 such as facsimile terminals where a complex file structure is
 difficult to support.

3.1.4 Practical Guidelines for Writing/Reading Multi-Page TIFF-F Files

 Traditionally, historical TIFF-F has required readers and writers to
 be able to handle multi-page TIFF-F files.  Based on the experience
 of various TIFF-F implementors, it has been seen that the
 implementation of TIFF-F can be greatly simplified if certain
 practical guidelines are followed when writing multi-page TIFF-F
 files.  However, for interchange robustness, TIFF-F readers SHOULD be
 prepared to read TIFF files whose structure is consistent with
 [TIFF], which supports a more flexible file structure than is
 recommended here.

Parsons & Rafferty Informational [Page 4] RFC 2306 TIFF-F Profile March 1998

 The structure for a multi-page TIFF-F file will include one IFD per
 page of the document.   Therefore, each IFD will define the
 attributes for a single page.   For simplicity, the writer of TIFF- F
 files SHOULD present IFDs in the same order as the actual sequence of
 pages.  (The pages are numbered within TIFF-F beginning with page 0
 as the first page and then ascending (i.e. 0, 1, 2,...).  However, as
 noted in section 3.1.3, any field values over 4 bytes will be stored
 separately from the IFD. TIFF-F readers SHOULD expect IFDs to be
 presented in page order, but be able to handle exceptions.
 Per [TIFF], the exact placement of image data is not specified.
 However, the strip offsets for each strip of image are defined from
 within each IFD.   Where possible, a second simplifying assumption
 for the writing of TIFF-F files is to specify that the image data for
 each page of a multi-page document SHOULD be contained within a
 single strip (i.e. one image strip per fax page).   The use of a
 single image strip per page is very useful for implementations such
 as store and forward messaging, where the file is usually prepared in
 advance of the transmission, but other assumptions may apply for the
 size of the image strip for implementations which require the use of
 "streaming" techniques (see section 3.7.6).  In the event a different
 image strip size assumption has been used (e.g. constant size for
 image strips which may be less than the page size), this will
 immediately be evident from the values/offsets of the fields that are
 related to strips.   From the TIFF-F reader standpoint, one image
 strip per page permits the image data to be found through reference
 via a single offset, resulting in a much simplified image structure
 and faster processing.
 A third simplifying assumption is that each IFD SHOULD be placed in
 the TIFF-F file structure at a point which precedes the image which
 the IFD describes.  If any long field values are present (see section
 3.1.3) then these SHOULD be placed after their referencing IFD and
 before the image data they describe.
 A fourth simplifying assumption for TIFF-F writers and readers is to
 place the actual image data in a physical order within the TIFF file
 structure which is consistent with the logical page order.  In
 practice, TIFF-F readers will need to use the strip offsets to find
 the exact physical location of the image data, whether or not it is
 presented in logical page order.
 TIFF-F writers MAY make a fifth simplifying assumption, in which the
 IFD, the value data and the image data for which the IFD has offsets
 precede the next image IFD. These elements MUST precede the next
 image IFD in the minimum set TIFF-F files (see section 3.6.2).
 However, this principle has been relaxed in the case of TIFF-F to
 reflect past practices.

Parsons & Rafferty Informational [Page 5] RFC 2306 TIFF-F Profile March 1998

 So, a TIFF-F file which is structured using the guidelines of this
 section will essentially be composed of a linked list of IFDs,
 presented in ascending page order, which in turn each point to a
 single page of image data (one strip per page), where the pages of
 image data are also placed in a logical page order within the TIFF-F
 file structure.  (The pages of image data may themselves be stored in
 a contiguous manner, at the option of the implementor).

3.2 Baseline TIFF Required Fields for BiLevel Images

 Baseline TIFF per [TIFF] requires that the following fields be
 present for all BiLevel Images:  ImageWidth, ImageLength,
 Compression, PhotometricInterpretation, StripOffsets, RowsPerStrip,
 StripByteCounts, XResolution, YResolution and ResolutionUnit.  TIFF-F
 uses all of these fields, but in some cases specifies a different
 range of acceptable values than Baseline TIFF.   Per [TIFF], if
 fields are omitted, the Baseline TIFF default value(if specified)
 will apply.
 In the field definitions which follow in this section and subsequent
 sections, the fields will be presented in the following form:
 Fieldname (tag-number) = values (if applicable). TYPE
 A brief summary of the Baseline TIFF fields and their use in TIFF-F
 follows:
 ImageWidth(256) = 1728, 2048, 2432, 2592, 3072, 3648, 3456, 4096,
                   4864.
     SHORT or LONG.  These are the fixed page widths in pixels.  The
     permissible values are dependent upon X and Y resolutions as
     shown in sections 2 and 3 of [T.4] and reproduced here for
     convenience:
     XResolution x Yresolution                  | ImageWidth
    --------------------------------------------|------------------
     204x98, 204x196, 204x391, 200x100, 200x200 | 1728, 2048, 2432
     300x300                                    | 2592, 3072, 3648
     408x391, 400x400                           | 3456, 4096, 4864
    --------------------------------------------|------------------
     Historical TIFF-F did not include support for the following
     widths related to higher resolutions:  2592, 3072, 3648, 3456,
     4096 and 4864.   Historical TIFF-F documents also included the
     following values related to A5 and A6 widths:  816 and 1216.  Per
     the most recent version of [T.4], A5 and A6 documents are no

Parsons & Rafferty Informational [Page 6] RFC 2306 TIFF-F Profile March 1998

     longer supported in Group 3 facsimile, so the related width
     values are now obsolete.  See section 3.8.2 for more information
     on inch/metric equivalencies and other implementation details.
 ImageLength (257).  SHORT or LONG. LONG recommended.
     The total number of scan lines in the image.
 Compression (259) = 3,4.  SHORT.
     This is a required TIFF-F field.  The permitted values for TIFF-
     F purposes are 3 and 4 as shown.   The default value per Baseline
     TIFF is 1 (Uncompressed), but this value is invalid for facsimile
     images.    Baseline TIFF also permits use of value 2 (Modified
     Huffman encoding), but the data is presented in a form which does
     not contain EOLs. Instead, TIFF-F specifies the value 3 for
     encoding one-dimensional T.4 Modified Huffman or 2-dimensional
     Modified READ data.   The detailed settings which apply for T.4
     encoded data are specified using the T4Options field.  TIFF-F
     also permits use of the value 4 for the compression field, which
     indicates that the data is coded using a [T.6] compression method
     (i.e the Modified Modified READ two-dimensional method). The
     detailed settings which apply for T.6 encoded data are specified
     using the T6Options field.
     Please refer to the definitions of the T4Options and T6Options
     fields in section 3.3, and section 3.8 for more information on
     the encoding of images and conventions used within TIFF-F.
 PhotometricInterpretation (260) = 0,1.  SHORT.
     This field allows notation of an inverted ("negative") image:
             0 = normal
             1 = inverted
 StripOffsets (273).  SHORT or LONG.
     For each strip, the offset of that strip.  The offset is measured
     from the beginning of the file. If a page is expressed as one
     large strip, there is one such entry per page.
 RowsPerStrip (278).  SHORT or LONG.  LONG recommended.
     The number of scan lines per strip.  When a page is expressed as
     one large strip, this is the same as the ImageLength field.
 StripByteCounts (279).  LONG or SHORT.  LONG recommended.
     For each strip, the number of bytes in that strip. If a page is
     expressed as one large strip, this is the total number of bytes
     in the page after compression.  Note that the choice of LONG or
     SHORT depends upon the size of the strip.

Parsons & Rafferty Informational [Page 7] RFC 2306 TIFF-F Profile March 1998

 ResolutionUnit (296) = 2,3.  SHORT.
     The units of measure for resolution:
             2 = Inch
             3 = Centimeter
     TIFF-F has traditionally used inch based measures.
 XResolution (282) = 204, 200, 300, 400, 408 (inches). RATIONAL.
     The horizontal resolution of the TIFF-F image expressed in pixels
     per resolution unit. The values of 200 and 408 have been added to
     the historical TIFF-F values, for consistency with [T.30].  Some
     existing TIFF-F implementations may also support values of 77
     (cm).  See section 3.8.2 for more information on inch/metric
     equivalencies and other implementation details.
 YResolution (283) = 98, 196, 100, 200, 300, 391, 400  (inches).
                     RATIONAL.
     The vertical resolution of the TIFF-F image expressed in pixels
     per resolution unit. The values of 100, 200, and 391 have been
     added to the historical TIFF-F values, for consistency with
     [T.30].  Some existing TIFF-F implementations may also support
     values of 77, 38.5 (cm). See section 3.8.2 for more information
     on inch/metric equivalencies and other implementation details.

3.3 TIFF-F Required Fields

 In addition to the Baseline TIFF fields, there are additional
 required fields for TIFF-F. A review of the additional required
 fields for TIFF-F follows:
 BitsPerSample (258) = 1.  SHORT.
     Since TIFF-F  is only used for black-and-white facsimile images,
     the value is  1 (the default) for all files.
 FillOrder (266) = 1, 2.  SHORT.
     TIFF  F readers must be able to read data in both bit orders, but
     the vast majority of facsimile products store data LSB first,
     exactly as it appears on the telephone line.
             1 = Most Significant Bit first.
             2 = Least Significant Bit first.
 NewSubFileType (254)= (Bit 1 = 1).  LONG.
     This field is made up of 32 flag bits.  Unused bits are
     expected to be 0 and bit 0 is the low order bit.   Bit 0 is set
     to 0 for TIFF-F.   Bit 1 is always set to 1 for TIFF-F,
     indicating a single page of a multi-page image. The same bit

Parsons & Rafferty Informational [Page 8] RFC 2306 TIFF-F Profile March 1998

     settings are used when TIFF-F is used for a one page fax image.
     See sections 3.1.1 and 3.1.2 for more details on the structure
     of multi-page TIFF-F image files.
 PageNumber (297).  SHORT/SHORT.
     This field specifies the page numbers in the fax document.  The
     field comprises two SHORT values: the first value is the page
     number, the second is the total number of pages. Single-page
     documents therefore use 0000/0001 hex.  If the second value is
     0, the total number of pages in the document is not available.
 SamplesPerPixel (277) = 1.  SHORT.
     The value of 1 denotes a bi-level, grayscale, or palette color
     image.
 There is also a requirement to include either the T4Options or the
 T6Options field in a TIFF-F IFD, depending upon the setting of the
 Compression field.  These fields are defined in the next section on
 TIFF extensions.

3.4 TIFF-F Extensions

 These are fields which are extensions beyond the required TIFF-F
 fields.  The following fields have been defined as extensions in
 [TIFF].
 T4Options (292) (Bit 0 = 0 or 1, Bit 1 = 0, Bit 2 = 0 or 1).  LONG.
     This field is required if the value for the compression field
     has been set to 3.   The values are set as shown below for TIFF-
     F.   For TIFF-F, uncompressed data is not allowed and EOLs MAY
     be byte aligned (see section 3.8.3).
             bit 0 = 0 for 1-Dimensional, 1 for 2-Dimensional (MR)
             bit 1 = must be 0 (uncompressed data not allowed)
             bit 2 = 0 for non-byte-aligned EOLs or 1 for byte-
                     aligned EOLs
     This field is made up of a set of 32 flag bits. Unused bits
     must be set to 0.  Bit 0 is the low order bit.  Please note
     that T4Options was known as G3Options in earlier versions of
     TIFF and TIFF-F.  The data in a TIFF-F image encoded using
     one of the T.4 methods is not terminated with an RTC (see
     section 3.8.5).
 T6Options (293) = (Bit 0 = 0, Bit 1 = 0)  LONG.
     This field is required for TIFF-F if value of the compression
     field has been set to 4. The value for this field is made up of
     a set of 32 flag bits.   Setting bit 0 to 0 indicates that the
     data is compressed using the Modified Modified READ (MMR) two-

Parsons & Rafferty Informational [Page 9] RFC 2306 TIFF-F Profile March 1998

     dimensional compression method.  MMR compressed Data is two-
     dimensional and does not use EOLs. Each MMR encoded image MUST
     include an "end-of-facsimile-block" (EOFB) code at the end of
     each coded strip (see section 3.8.6). Uncompressed data is not
     applicable for bi-level facsimile images, so that bit 1 must be
     set to 0.  Unused bits must be set to 0. Bit 0 is the low-order
     bit. The default value is 0 (all bits 0).
             bit 0 = 0 for 2-Dimensional
             bit 1 = must be 0 (uncompressed data not allowed)
     In earlier versions of TIFF, this field was named Group4Options.
     The significance has not changed and the present definition is
     compatible.
     In addition, three new fields, defined as TIFF-F extensions,
     describe page quality.  The information contained in these fields
     is usually obtained from receiving facsimile hardware (if
     applicable).   These fields are optional.  They SHOULD NOT be
     used in writing TIFF-F files for facsimile image data that is
     error corrected or otherwise guaranteed not to have coding
     errors.
     Some implementations need to understand exactly the error content
     of the data.  For example, a CAD program might wish to verify
     that a file has a low error level before importing it into a
     high- accuracy document.  Because Group 3 facsimile devices do
     not necessarily perform error correction on the image data, the
     quality of a received page must be inferred from the pixel count
     of decoded scan lines. A "good" scan line is defined as a line
     that, when decoded, contains the correct number of pixels.
     Conversely, a "bad" scan line is defined as a line that, when
     decoded, comprises an incorrect number of pixels.
     BadFaxLines (326). SHORT or LONG
     This field reports the number of scan lines with an incorrect
     number of pixels encountered by the facsimile during reception
     (but not necessarily in the file).
     Note: PercentBad = (BadFaxLines/ImageLength) * 100
 CleanFaxData (327). SHORT
     N =
         0 = Data contains no lines with incorrect pixel counts or
            regenerated lines  (i.e., computer generated)
         1 = Lines with an incorrect pixel count were regenerated by
            receiving device

Parsons & Rafferty Informational [Page 10] RFC 2306 TIFF-F Profile March 1998

         2 = Lines with an incorrect pixel count are in the data  and
            were not regenerated by receiving device (i.e. data
            contains bad scan lines)
     Many facsimile devices do not actually output bad lines.
     Instead, the previous good line is repeated in place of a bad
     line. Although this substitution, known as line regeneration,
     results in a visual improvement to the image, the data is
     nevertheless corrupted.  The CleanFaxData field describes the
     error content of the data.  That is, when the BadFaxLines and
     ImageLength fields indicate that the facsimile device
     encountered lines with an incorrect number of pixels during
     reception, the CleanFaxData field indicates whether these bad
     lines are actually still in the data or if the receiving
     facsimile device replaced them with regenerated lines.
 ConsecutiveBadFaxLines (328). LONG or SHORT.
     This field reports the maximum number of consecutive lines
     containing an incorrect number of pixels encountered by the
     facsimile device during reception (but not necessarily in the
     file).
     The BadFaxLines and ImageLength data indicate only the quantity
     of such lines.  The ConsecutiveBadFaxLines field is an
     indicator of their distribution and may therefore be a better
     general indicator of perceived image quality.

3.5 Recommended Fields

 hese are fields that MAY be used in encoding TIFF-F files, but are
 ptional in nature and may be ignored by many TIFF readers.  These
 ields are called recommended consistent with historical TIFF-F
 ractice.
 BadFaxLines (326) [defined in section 3.4]
 CleanFaxData (327) [defined in section 3.4]
 ConsecutiveBadFaxLines (328) [defined in section 3.4]
 DateTime (306).  ASCII.
     Date and time in the format YYYY:MM:DD HH:MM:SS, in 24-hour
     format. String length including NUL byte is 20 bytes. Space
     between DD and HH.
 DocumentName (269).  ASCII.
     This is the name of the document from which the document was
     scanned.

Parsons & Rafferty Informational [Page 11] RFC 2306 TIFF-F Profile March 1998

 ImageDescription (270).  ASCII.
     This is an ASCII string describing the contents of the image.
 Orientation (274).  SHORT.
     This field is designated as "Recommended" for consistency with
     historical TIFF-F, but is also a Baseline TIFF field with a
     default value of 1 per [TIFF]. The default value of 1 applies
     if the field is omitted, but for clarity, TIFF-F writers SHOULD
     include this field.  This field might be useful for displayers
     that always want to show the same orientation, regardless of
     the image.  The default value of 1 is "0th row is visual top of
     image, and 0th column is the visual left."  An 180-degree
     rotation is 3.  See [TIFF] for an explanation of other values.
 Software (305).  ASCII.
     The optional name and release number of the software package
     that created the image.

3.6 Requirements for TIFF-F Minimum Subset

 This section defines the requirements for a minimum subset of TIFF-F
 fields and values that all TIFF-F readers SHOULD support to maximize
 interoperability with current and historical TIFF-F implementations.
 The TIFF-F structure for writing minimum subset files is also
 defined.

3.6.1 Summary of Minimum Subset Fields and Values

 A summary of the minimum subset TIFF-F fields and values is provided
 in the following table.  The required fields for the minimum subset
 are shown under the column labeled "Field".  The values for these
 fields in the minimum subset are shown under the column labeled
 "Minimum".
Field             | Minimum      | Comment
------------------|--------------|-------------------------------
BitsPerSample     | 1            |one bit per sample
Compression       | 3            |3 for T.4 (MH)
FillOrder         | 2            |LSB first
ImageWidth        | 1728         |
ImageLength       |              |required
NewSubFileType    | Bit 1 = 1    |single page of multipage file
PageNumber        | X/X          |pg/tot, 0 base, tot in 1st IFD
PhotometricInterp | 0            |0 is white
ResolutionUnit    | 2            |inches (default)
RowsPerStrip      |=ImageLength  |
SamplesPerPixel   | 1            |one sample per pixel

Parsons & Rafferty Informational [Page 12] RFC 2306 TIFF-F Profile March 1998

StripByteCounts   |              |required
StripOffsets      |              |required
T4Options         | Bit 0 = 0    |MH
                  | Bit 1 = 0    |
                  | Bit 2 = 0,1  |Non-Byte-aligned,
                  |              | Byte-Aligned EOLs
XResolution       | 204          |Units is per inch
YResolution       | 196,98       |Units is per inch
------------------|--------------|------------------------------

3.6.2 TIFF-F Minimum Subset File Structure

 For implementations which need to write minimum subset TIFF-F files,
 the file structure shown in Figure 3.1 MUST be used:
                 +-----------------------+
                 |         Header        |------------+
                 +-----------------------+            | First IFD
                 |      IFD (page 0)     | <----------+ Offset
             +---|                       |------------+
             |   |                       |--+         |
       Value |   +-----------------------+  |         |
      Offset +-->|      Long Values      |  |         |
                 +-----------------------|  | Strip   |
                 |  Image Data (page 0)  |<-+ Offset  |
                 +-----------------------+            | Next IFD
                 |      IFD (page 1)     | <----------+ Offset
             +---|                       |------------+
             |   |                       |--+         |
       Value |   +-----------------------+  |         |
      Offset +-->|      Long Values      |  |         |
                 +-----------------------|  | Strip   |
                 |  Image Data (page 1)  |<-+ Offset  |
                 +-----------------------+            | Next IFD
                 |      IFD (page 2)     | <----------+ Offset
                 +-----------------------+
                 |          :            |
                 |          :            |
     Figure 3.1     TIFF-F Minimum Subset File Structure
 As depicted in Figure 3.1, the IFD of each page precedes the related
 Image Data for that page.  If present, any long field values appear
 between the IFD and the image data for that page.  For multiple page
 documents, each IFD/image pair is immediately followed by the next
 IFD/image pair in logical page order within the file structure, until
 all pages have been defined.

Parsons & Rafferty Informational [Page 13] RFC 2306 TIFF-F Profile March 1998

 The format for the TIFF Header is as defined in [TIFF].  When writing
 TIFF-F minimum subset files, the value for the byte order in the
 Header SHOULD be II (0x4949, denoting that the bytes in the TIFF file
 are in LSB first (little-endian) order.
 This results in a TIFF header whose content is as shown in Figure
 3.2.
 | Offset |   Description     | Type   |     Value          |
 +--------+-------------------+--------+--------------------+
 |   0    |   Byte Order      | Short  |  0x4949 (II)       |
 +--------+-------------------+--------+--------------------+
 |   2    |   Version         | Short  |  42                |
 +--------+-------------------+--------+--------------------+
 |   4    | Offset of 0th IFD | Long   |  0x 0000 0008      |
 +--------+-------------------+--------+--------------------+
 Figure 3.2: Image File Header for Minimum Subset TIFF-F Files

3.7 Technical Implementation Issues

3.7.1 Strips

 Those new to TIFF may not be familiar with the concept of "strips"
 embodied in the three fields RowsPerStrip, StripByteCount,
 StripOffsets.
 In general, third-party implementations that read and write TIFF
 files expect the image to be divided into "strips," also known as
 "bands."  Each strip contains a few lines of the image. By using
 strips, a TIFF reader need not load the entire image into memory,
 thus enabling it to fetch and decompress small random portions of the
 image as necessary.
 The dimensions of a strip are described by the RowsPerStrip and
 StripByteCount fields.  The location in the TIFF file of each strip
 is contained in the StripOffsets field.
 The size of TIFF-F strips is application dependent.  The recommended
 approach for multi-page TIFF-F images is to represent each page as a
 single strip.

Parsons & Rafferty Informational [Page 14] RFC 2306 TIFF-F Profile March 1998

3.7.2 Bit Order

 The default bit order in Baseline TIFF per [TIFF] is indicated by
 FillOrder=1, where bits are not reversed before being stored.
 However, TIFF-F typically utilizes the setting of FillOrder=2, where
 the bit order within bytes is reversed before storage (i.e., bits are
 stored with the Least Significant Bit first).
 Facsimile data appears on the phone line in bit-reversed order
 relative to its description in CCITT Recommendation T.4.  Therefore,
 a wide majority of facsimile implementations choose this natural
 order for storage. Nevertheless, TIFF-F readers must be able to read
 data in both bit orders.

3.7.3 Multi-Page

 Many existing implementations already read TIFF-F like files, but do
 not support the multi- page field.  Since a multi-page format greatly
 simplifies file management in fax application software, TIFF-F
 specifies multi-page documents (NewSubfileType = 2) as the standard
 case.

3.7.4 Compression

 In Group 3 facsimile, there are three compression methods which had
 been standardized as of 1994 and are in common use.  The ITU-T T.4
 recommendation defines a one-dimensional compression method known as
 Modified Huffman (MH) and a two-dimensional method known as Modified
 READ (MR) (READ is short for Relative Element Address Designate).  In
 1984, a somewhat more efficient compression method known as Modified
 Modified READ (MMR) was defined in the T.6 recommendation.  It was
 originally defined for use with Group 4 facsimile, so that this
 compression method has been commonly called Group 4 compression.  In
 1991, the MMR method was approved for use in Group 3 facsimile and
 has since been widely utilized.
 TIFF-F permits three different compression methods.  In the most
 common practice, the one-dimensional compression method (Modified
 Huffman) is used.  This is specified by setting the value of the
 Compression field to 3 and then setting bit 0 of the T4Options field
 to 0.  Alternatively, the two dimensional Modified READ method (which
 is much less frequently used in historical TIFF-F implementations)
 may be selected by setting bit 0 to a value of 1.
 Optionally, depending upon the implementation requirements, the more
 efficient two-dimensional compression method from T.6 (i.e.  MMR or
 "Group 4 compression") may be selected.  This method is selected by

Parsons & Rafferty Informational [Page 15] RFC 2306 TIFF-F Profile March 1998

 setting the value of the Compression field to 4 and then setting the
 value of the first two bits (and all unused bits) of T6options to 0.
 More information to aid the implementer in making a compression
 selection is contained in section 3.8 on Implementation Warnings.

3.7.5 Example Use of Page-quality Fields

 Here are examples for writing the CleanFaxData,  BadFaxLines, and
 ConsecutiveBadFaxLines fields:
     1.  Facsimile hardware does not provide page quality
         information: MUST NOT write page-quality fields.
     2.  Facsimile hardware provides page quality information, but
         reports no bad lines.  Write only BadFaxLines = 0.
     3.  Facsimile hardware provides page quality information, and
         reports bad lines.  Write both BadFaxLines and
         ConsecutiveBadFaxLines.  Also write CleanFaxData = 1 or 2 if
         the hardware's regeneration capability is known.
     4.  Source image data stream is error-corrected or otherwise
         guaranteed to be error-free such as for a computer generated
         file:  SHOULD NOT write page-quality fields.

3.7.6 Use of TIFF-F for Streaming Applications

 TIFF-F has historically been used for handling fax image files in
 implementations such as store and forward messaging where the entire
 size of the file is known in advance.  While TIFF-F may also possibly
 be used as a file format for cases such as streaming applications,
 different assumptions may be required than those provided in this
 document (e.g., the entire size and number of pages within the image
 are not known in advance).  As a result, a definition for the
 streaming application of TIFF-F is beyond the scope of this document.

3.7.7 TIFF-F Export and Import

 Fax implementations that do not wish to support TIFF-F as a native
 format may elect to support it as import/export medium.
 Export
 It is recommended that implementations export multiple page TIFF-F
 files without manipulating fields and values.   Historically, some
 TIFF-F writers have attempted to produce individual single-page
 TIFF-F files with modified NewSubFileType and PageNumber (page one-
 of-one) values for export purposes.  However, there is no easy way to
 link such multiple single page files together into a logical multiple
 page document, so that this practice is not recommended.

Parsons & Rafferty Informational [Page 16] RFC 2306 TIFF-F Profile March 1998

 Import
 A TIFF-F reader MUST be able to handle a TIFF-F file containing
 multiple pages.

3.8 Implementation Warnings

 3.8.1  Uncompressed data
 TIFF-F requires the ability to read and write at least one-
 dimensional T.4 Huffman ("compressed") data.  Uncompressed data is
 not allowed.  This means that the "Uncompressed" bit in T4Options or
 T6Options must be set to 0.

3.8.2 Encoding and Resolution

 Since two-dimensional encoding is not required for Group 3
 compatibility, some historic TIFF-F readers have not been able to
 read such files.  The minimum subset of TIFF-F REQUIRES support for
 one dimensional (Modified Huffman) files, so this choice maximizes
 portability.  However, implementers seeking greater efficiency SHOULD
 use T.6 MMR compression when writing TIFF-F files.  Some TIFF-F
 readers will also support two-dimensional Modified READ files.
 Implementers that wish to have the maximum flexibility in reading
 TIFF-F files SHOULD support all three of these compression methods
 (MH, MR and MMR).
 For the case of resolution, almost all facsimile products support
 both standard (98 dpi) vertical resolution  and "fine" (196 dpi)
 resolution.  Therefore, fine-resolution files are quite portable in
 the real world.
 In 1993, the ITU-T added support for higher resolutions in the T.30
 recommendation including 200 x 200, 300 x 300, 400 x 400 in dots per
 inch based units.  At the same time, support was added for metric
 dimensions which are equivalent to the following inch based
 resolutions: 391v x 204h and 391v x 408h.  Therefore, the full set of
 inch-based equivalents of the new resolutions are supported in the
 TIFF-F writer, since they may appear in some image data streams
 received from Group 3 facsimile devices.  However, many facsimile
 terminals and older versions of  TIFF-F readers are likely to not
 support the use of these higher resolutions.
 Per [T.4], it is permissible for implementations to treat the
 following XResolution values as being equivalent: <204,200> and
 <400,408>.  In a similar respect, the following YResolution values

Parsons & Rafferty Informational [Page 17] RFC 2306 TIFF-F Profile March 1998

 may also be treated as being equivalent: <98, 100>, <196, 200>, and
 <391, 400>.   These equivalencies were allowed by [T.4] to permit
 conversions between inch and metric based facsimile terminals.
 In a similar respect, the optional support of metric based
 resolutions in the TIFF-F reader (i.e. 77 x 38.5 cm) is included for
 completeness, since they are used in some legacy TIFF-F
 implementations, but this use is not recommended for the creation of
 TIFF-F files by a writer.

3.8.3 EOL byte-aligned

 The historical convention for TIFF-F has been that all EOLs in
 Modified Huffman or Modified READ data must be byte-aligned.
 However, Baseline TIFF has permitted use of non-byte-aligned EOLs by
 default, so that a large percentage of TIFF-F reader implementations
 support both conventions.   Therefore, the minimum subset of TIFF-F
 as defined in this document includes support for both byte-aligned
 and non-byte-aligned EOLs.
 An EOL is said to be byte-aligned when Fill bits have been added as
 necessary before EOL codes such that EOL always ends on a byte
 boundary, thus ensuring an  EOL-sequence of a one byte preceded by a
 zero nibble: xxxx0000 00000001.
 Modified Huffman encoding encodes bits, not bytes. This means that
 the end-of-line token may end in the middle of a byte. In byte
 alignment, extra zero bits (Fill) are added so that the first bit of
 data following an EOL begins on a byte boundary. In effect, byte
 alignment relieves application software of the burden of bit-
 shifting every byte while parsing scan lines for line-oriented image
 manipulation (such as writing a TIFF file).
 For Modified READ encoding, each line is terminated by an EOL and a
 one bit tag bit.  Per [T.4], the value of the tag bit is 0 if the
 next line contains two dimensional data and 1 if the next line is a
 reference line.   To maintain byte alignment, fill bits are added
 before the EOL/tag bit sequence, so that the first bit of data
 following an MR tag bit begins on a byte boundary.

3.8.4 EOL

 As illustrated in FIGURE 1/T.4 in [T.4], facsimile documents encoded
 with Modified Huffman begin with an EOL (which in TIFF-F may be
 byte-aligned). The last line of the image is not terminated by an
 EOL.  In a similar respect, images encoded with Modified READ two
 dimensional encoding begin with an EOL, followed by a tag bit.

Parsons & Rafferty Informational [Page 18] RFC 2306 TIFF-F Profile March 1998

3.8.5 RTC Exclusion

 Aside from EOLs, TIFF-F files have historically only contained image
 data. This means that implementations which wish to maintain strict
 conformance with the rules in [TIFF] and compatibility with
 historical TIFF-F, SHOULD NOT include the Return To Control sequence
 (RTC) (consisting of 6 consecutive EOLs) when writing TIFF- F files.
 However, implementations which need to support "transparency" of
 [T.4] image data MAY include RTCs when writing TIFF-F files if the
 flag settings of the T4Options field are set for non-byte aligned MH
 or MR image data.  Implementors of TIFF readers should also be aware
 that there are some existing TIFF-F implementations which include the
 RTC sequence in MH/MR image data.  Therefore, TIFF-F readers MUST be
 able to process files which do not include RTCs and SHOULD be able to
 process files which do include RTCs.

3.8.6 Use of EOFB for T.6 Compressed Images

 TIFF-F pages which are encoded with the T.6 Modified Modified READ
 compression method MUST include an "end-of-facsimile-block" (EOFB)
 code at the end of each coded strip. Per [TIFF], the EOFB code is
 followed by pad bits as needed to align on a byte boundary.   TIFF
 readers SHOULD ignore any bits other than pad bits beyond the EOFB.

3.9 TIFF-F Fields Summary

 Implementations may choose to implement a TIFF-F Reader, TIFF-F
 Writer or both, depending upon application requirements.  The TIFF- F
 Reader is typically used to read an existing TIFF-F file which
 resides on a computer or peripheral device.  The TIFF-F Writer is
 typically used to convert a bi-level image bit stream into a TIFF-F
 compliant file. For many Internet applications, only the Reader needs
 to be implemented. The specific field support required for TIFF-F
 Readers and Writers is summarized below.

3.9.1 TIFF Reader

 The fields in the following table are specified for a TIFF-F Reader.
 The range of values for required and recommended fields are as shown.
 The minimum subset of values are also shown. If required fields are
 omitted in a TIFF-F file, the Baseline TIFF default value will apply.
 Image data must not have any coding errors. In the table, certain
 fields have a value that is a sequence of flag bits (e.g. T4Options).
 An implementation should test the setting of the relevant flag bits
 individually to allow extensions to the sequence of flag bits to be
 appropriately ignored.

Parsons & Rafferty Informational [Page 19] RFC 2306 TIFF-F Profile March 1998

 As noted within [TIFF], a TIFF file begins with an 8-byte image file
 header, of which the first two bytes (0-1) contain the byte order
 within the file.  The permissible values are:
     II- Byte order from least significant byte to the most
         significant byte (little-endian)
     MM - byte order is always from most significant to least
         significant (big-endian)
 For a TIFF-F Reader, the legal values are:
     ByteOrder: MM,II (Either byte order is allowed)

3.9.1.1 Fields for TIFF-F Reader

 Recommended Fields in the table are shown with an asterisk (*).
 Other fields may be present, but they should be of an informational
 nature, so that a reader can elect to ignore them.
 Informational fields which are often present in TIFF-F images are:
    Software, Datetime, BadFaxLines, CleanFaxData and
    ConsecutiveBadFaxLines.
Field             | Values      | Minimum     | Comment
------------------|-------------|-------------|----------------------
BitsPerSample     | 1           | 1           |one bit per sample
Compression       | 3,4         | 3           |3 for T.4 (MH, MR)
                  |             |             |4 for T.6 - MMR
FillOrder         | 2,1         | 2           |LSB first or MSB first
ImageWidth        | 1728, 2048, | 1728        |depends on XResolution
                  | 2432, 2592, |             |
                  | 3072, 3648, |             |
                  | 3456, 4096, |             |
                  | 4864        |             |
ImageLength       | >0          |             |required
NewSubFileType    | Bit 1 = 1   | Bit 1 = 1   |single page of
                  |             |             |multipage file
Orientation *     | 1           |             |1st row=top left,
                  |             |             | 1st col=top
PageNumber        | X/X         | 0/1         |pg/tot, 0 base,
                  |             |             | tot in 1st IFD
PhotometricInterp | 0,1         | 0           |0 is white
ResolutionUnit    | 2,3         | 2           |inches (default)
RowsPerStrip      |=ImageLength |=ImageLength |
                  | or other    |             |
SamplesPerPixel   | 1           | 1           |one sample per pixel
StripByteCounts   | >0          |             |required

Parsons & Rafferty Informational [Page 20] RFC 2306 TIFF-F Profile March 1998

StripOffsets      | >0          |             |required
T4Options         | Bit 0 = 0,1 | Bit 0 = 0   |MH,MR(incl if not MMR)
                  | Bit 1 = 0   | Bit 1 = 0   |
                  | Bit 2 = 0,1 | Bit 2 = 0,1 | Non-Byte-aligned and
                  |             |             | Byte-Aligned EOLs
T6Options         | 0           |             |MMR (incl only if MMR)
XResolution       | 204,200,300,| 204         | If unit is per inch
                  | 400,408,    |             |
                  | 77          |             | If unit is per cm
YResolution       | 196,98,100, | 196,98      | If unit is per inch
                  | 200,300,391,|             |
                  | 400,        |             |
                  | 77,38.5     |             | If unit is per cm
------------------|-------------|-------------|----------------------

3.9.2 TIFF-F Writer

 For the case of writing (creating) a TIFF-F file format from an image
 data stream or other raster data, implementations SHOULD write files
 which can be read by a TIFF-F Reader as defined in 3.9.1.  It is
 recommended that all fields from the table in 3.9.1.1 SHOULD be
 included when writing TIFF-F files in order to  minimize dependencies
 on default values. Image data must not have any coding errors.
 Other fields may be present, but they should be of an informational
 nature, so that a Reader may elect to ignore them.
 For the case of writing "minimum subset" TIFF-F files, the rules
 defined in section 3.6 apply.
 Informational fields that may be useful for TIFF-F files are:
     Software, Datetime, BadFaxLines, ConsecutiveBadFaxLines
 TIFF Writers SHOULD only generate the fields that describe facsimile
 image quality when the image has been generated from a fax image data
 stream where error correction (e.g. Group 3 Error Correction Mode)
 was not used.  These fields are:  CleanFaxData, BadFaxLines and
 ConsecutiveBadFaxLines.

4. MIME sub-type image/tiff

 [TIFFREG] describes the registration of the MIME content-type image/
 tiff to refer to TIFF 6.0 encoded image data.   When transported by
 MIME, the TIFF content defined by this document must be encoded
 within an image/tiff content type. In addition, an optional
 "application" parameter is defined for image/tiff to identify a
 particular application's subset of TIFF and TIFF extensions for the

Parsons & Rafferty Informational [Page 21] RFC 2306 TIFF-F Profile March 1998

 encoded image data, if it is known. 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.

4.1 Refinement of MIME sub-type image/tiff for Application F

 Since this document defines a facsimile specific profile of TIFF, it
 is useful to note an appropriate application parameter for the
 image/tiff MIME content-type.
 The "faxbw" application parameter is defined for black and white
 facsimile.  It is suitable for use by applications that can process
 one or more TIFF for facsimile profiles or subsets used for the
 encoding of black and white facsimile data.
 Since this document defines a profile of TIFF for facsimile which is
 suitable for use with black and white facsimile image data,
 applications which use this profile or its minimum subset should set
 the value of the application parameter to "faxbw".
 An example of the use of the image/tiff MIME Content-type with the
 application parameter set with the value "faxbw" follows:
 Example:
        Content-type: image/tiff; application=faxbw
 In this example, use of this parameter value will enable applications
 to identify the content as being within a profile or subset of TIFF
 for Facsimile that is suitable for encoding black and white image
 data, before attempting to process the image data.

5. Implementation Usage

 5.1 Internet Fax Usage
 The usage of TIFF-F is envisioned as a component of Internet Fax.  It
 is anticipated that Internet Fax may use both a TIFF-F Reader and
 TIFF-F Writer. The details of the Internet Fax services and their use
 of TIFF-F will be specified in other documents.

5.2 VPIM Usage

 The Application F of TIFF (i.e. TIFF-F content) is a secondary
 component of the VPIM Message as defined in [VPIM2].  Voice messaging
 systems can often handle fax store-and-forward capabilities in
 addition to traditional voice message store-and- forward functions.

Parsons & Rafferty Informational [Page 22] RFC 2306 TIFF-F Profile March 1998

 As a result, TIFF-F fax messages can optionally be sent between
 compliant VPIM systems, and may be rejected if the recipient system
 cannot deal with fax.
 Refer to the VPIM Specification for proper usage of this content.

6. Security Considerations

 This document describes the encoding for TIFF-F, which is a profile
 of the TIFF encoding for facsimile.  As such, it does not create any
 security issues not already identified in [TIFFREG], in its use of
 fields as defined in [TIFF]. There are also new TIFF fields defined
 within this specification, but they are of a purely descriptive
 nature, so that no new security risks are incurred.
 Further, the encoding specified in this document does not in any way
 preclude the use of any Internet security protocol to encrypt,
 authenticate, or non-repudiate TIFF-F encoded facsimile messages.

7. 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

8. 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.

Parsons & Rafferty Informational [Page 23] RFC 2306 TIFF-F Profile March 1998

 [REQ] Bradner, S., "Key words for use in RFCs to Indicate
      Requirement Levels", RFC 2119, March 1997.
 [T.30] ITU-T Recommendation T.30 - "Procedures for Document
      Facsimile Transmission in the General Switched Telephone
      Network", June, 1996
 [T.4] ITU-T Recommendation T.4 - "Standardization of Group 3
      Facsimile Apparatus for Document Transmission", June, 1996
 [T.6] ITU-T Recommendation T.6 - "Facsimile Coding Schemes and
      Coding Control Functions for Group 4 Facsimile Apparatus",
      March, 1993
 [TIFF] Adobe Developers Association, TIFF (TM) Revision 6.0 -
      Final, June 3, 1992.
 [TIFFREG] Parsons, G., Rafferty, J. and S. Zilles, "Tag Image File
      Format (TIFF) - image/tiff:  MIME Sub-type Registration ", RFC
      2302, March 1998.
 [VPIM2] G. Vaudreuil and G. Parsons, "Voice Profile for Internet
      Mail - version 2", Work In Progress, <draft-ema-vpim-06.txt>,
      November 1997.

Parsons & Rafferty Informational [Page 24] RFC 2306 TIFF-F Profile March 1998

9. 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 & Rafferty Informational [Page 25]

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