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RFC2301 - File Format for Internet Fax

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

Network Working Group L. McIntyre

Request for Comments: 2301 Xerox Corporation

Category: Standards Track S. Zilles

Adobe Systems, Inc.

R. BUCkley

Xerox Corporation

D. Venable

Xerox Corporation

G. Parsons

Northern Telecom

J. Rafferty

Human Communications

March 1998

File Format for Internet Fax

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.

Abstract

This document describes the TIFF (Tag Image File Format)

representation of image data specified by the ITU-T Recommendations

for black-and-white and color facsimile. This file format

specification is commonly known as TIFF-FX. It formally defines

minimal, extended and lossless JBIG modes (Profiles S, F, J) for

black-and-white fax, and base JPEG, lossless JBIG and Mixed Raster

Content modes (Profiles C, L, M) for color and grayscale fax. These

modes or profiles correspond to the content of the applicable ITU-T

Recommendations. Files formatted according to this specification use

the image/tiff MIME Content Type.

Table of Contents

1. INTRODUCTION........................................................4

1.1. Scope..........................................................5

1.2. Approach.......................................................5

1.3. Overview of this draft.........................................5

2. TIFF and Fax........................................................7

2.1. TIFF Overview..................................................7

2.1.1. File Structure.............................................7

2.1.2. Image Structure............................................9

2.1.3. TIFF File Structure for Fax Applications..................10

2.2 TIFF Fields for All Fax Applications...........................11

2.2.1. TIFF Fields required for all fax modes....................12

2.2.2. Additional TIFF Fields required for all fax modes.........13

2.2.3. TIFF Fields recommended for all fax modes.................15

2.2.4. New TIFF Fields recommended for fax modes.................16

3. Minimal Black-and-White Fax Mode...................................18

3.1. Overview......................................................18

3.2. Required TIFF Fields..........................................18

3.2.1 Baseline Fields............................................18

3.2.2 Extension Fields...........................................20

3.2.3 New Fields.................................................20

3.3. Recommended TIFF Fields.......................................20

3.4. End of Line (EOL) and Return to Control (RTC).................20

3.4.1 RTC Exclusion..............................................21

3.5. File Structure................................................22

3.6. Minimal Black-and-White Mode Summary..........................23

4. Extended Black-and-White Fax Mode..................................24

4.1. TIFF-F Overview...............................................25

4.2. Required TIFF Fields..........................................26

4.2.1. Baseline Fields...........................................26

4.2.2. Extension Fields..........................................28

4.2.3. New Fields................................................29

4.3. Recommended TIFF Fields.......................................29

4.3.1. Baseline Fields...........................................29

4.3.2. Extension Fields..........................................29

4.3.3. New Fields................................................29

4.4. Technical Implementation Issues...............................30

4.4.1. Strips....................................................30

4.4.2. Bit Order.................................................31

4.4.3. Multi-Page................................................31

4.4.4. Compression...............................................31

4.4.5. Example Use of Page-quality Fields........................32

4.4.6. Practical Guidelines for Writing and Reading Multi-Page

TIFF-F Files..............................................33

4.4.7. Use of TIFF-F for Streaming Applications..................34

4.5. Implementation Warnings.......................................34

4.5.1. Uncompressed Data.........................................34

4.5.2. Encoding and Resolution...................................35

4.5.3. EOL byte-aligned..........................................35

4.5.4. EOL.......................................................36

4.5.5. RTC Exclusion.............................................36

4.5.6. Use of EOFB for T.6 Compressed Images.....................37

4.6. Example Use of TIFF-F.........................................37

4.7. Extended Black-and-white Fax Mode Summary.....................37

5. Lossless JBIG Black-and-White Fax Mode.............................39

5.1. Overview......................................................40

5.2. Required TIFF Fields..........................................40

5.2.1. Baseline Fields...........................................40

5.2.2. Extension Fields..........................................40

5.2.3. New Fields................................................41

5.3. Recommended TIFF Fields.......................................41

5.4. Lossless JBIG Black-and-White Mode Summary....................41

6. Base Color Fax Mode................................................43

6.1. Overview......................................................43

6.2. Required TIFF Fields..........................................43

6.2.1. Baseline Fields...........................................43

6.2.2. Extension Fields..........................................45

6.2.3. New Fields................................................46

6.3. Recommended TIFF Fields.......................................47

6.4. Base Color Fax Mode Summary...................................47

7. Lossless Color Mode................................................49

7.1. Overview......................................................50

7.1.1. Color Encoding............................................50

7.1.2. JBIG Encoding.............................................50

7.2. Required TIFF Fields..........................................51

7.2.1. Baseline Fields...........................................51

7.2.2. Extension Fields..........................................52

7.2.3. New Fields................................................53

7.3. Recommended TIFF Fields.......................................53

7.4. Lossless Color Fax Mode Summary...............................53

8. Mixed Raster Content Mode..........................................55

8.1 Overview.......................................................55

8.1.1. MRC 3-layer model.........................................55

8.1.2. A TIFF Representation for the MRC 3-layer model...........56

8.2. Required TIFF Fields..........................................58

8.2.1. Baseline Fields...........................................58

8.2.2. Extension Fields..........................................59

8.2.3. New Fields................................................60

8.3. Recommended TIFF Fields.......................................62

8.4. Rules and Requirements for Images.............................62

8.5. MRC Fax Mode Summary..........................................63

9. MIME content-type image/tiff.......................................66

9.1 Refinement of MIME content-type image/tiff for Facsimile

Applications...................................................66

10. Security Considerations...........................................67

11. References........................................................67

12. Authors' Addresses................................................69

Annex A: Summary of TIFF Fields for Internet Fax .....................70

Annex B. IANA Registration for image/tiff Application Parameter

Values used for facsimile....................................75

Full Copyright Statement..............................................77

1. Introduction

This document describes the use of TIFF (Tag Image File Format) to

represent the data content and structure generated by the current

suite of ITU-T Recommendations for Group 3 facsimile. These

Recommendations and the TIFF fields described here support the

following facsimile modes or profiles:

S: minimal black-and-white mode, using binary MH compression

[T.4]

F: extended black-and-white mode, using binary MH, MR and MMR

compression [T.4, T.6]

J: lossless JBIG black-and-white mode, with JBIG compression

[T.85, T.82]

C: lossy color and grayscale mode, using JPEG compression

[T.42, T.81]

L: lossless color and grayscale mode, using JBIG compression

[T.43, T.82]

M: mixed raster content mode [T.44], using a combination of

existing compression methods

Each profile corresponds to the content of ITU-T Recommendations

shown and is a subset of the full TIFF for facsimile specification.

Profile S describes a minimal interchange set of fields, which will

guarantee that, at least, binary black-and-white images will be

supported. Implementations are required to support this minimal

interchange set of fields.

With the intent of specifying a file format for Internet Fax, this

draft:

1. specifies the structure of TIFF files for facsimile data,

2. defines ITU fax-compatible values for existing TIFF fields,

3. defines new TIFF fields and values required for compatibility

with ITU color fax.

This specification of TIFF for facsimile is known as TIFF-FX.

1.1 Scope

This document defines a TIFF-based file format specification for

enabling standardized messaging-based fax over the Internet. It

specifies the TIFF fields and field values required for compatibility

with the existing ITU-T Recommendations for Group 3 black-and-white,

grayscale and color facsimile. TIFF has historically been used for

handling fax image files in applications such as store-and-forward

messaging. Implementations that support this file format

specification for import/eXPort may elect to support it as a native

format. This document recommends a TIFF file structure that is

compatible with low-memory and page-level streaming implementations.

Unless otherwise noted, the current TIFF specification [TIFF] and

selected TIFF Technical Notes [TTN1, TTN2] are the primary references

for describing TIFF and defining TIFF fields. This document is the

primary reference for defining TIFF field values for fax

applications.

1.2 Approach

The basic approach to using TIFF for facsimile data is to insert the

compressed fax image data in a TIFF file and use TIFF fields to

encode the parameters that describe the image data. These fields will

have values that comply with the ITU-T Recommendations. The MIME

content type of the resulting file will be image/tiff, with an

optional Application parameter [TIFF-REG]; see Section 9.

This approach takes advantage of TIFF features and structures that

bridge the data formats and performance requirements of both legacy

fax machines and host-based fax applications. TIFF constructs for

pages, images, and strips allow a TIFF file to preserve the fax data

stream structure and the performance advantages that come with it. A

TIFF-based approach also builds on an established base of users and

implementors and ensures backward compatibility with existing TIFF-

based IETF proposals and work in progress for Internet fax.

1.3 Overview of this draft

Section 2 gives an overview of TIFF. Section 2.1 describes the

structure of TIFF files, including general guidelines for structuring

multi-page TIFF files. Section 2.2 lists the TIFF fields that are

required or recommended for all fax modes. The TIFF fields used only

by specific fax modes are described in Sections 3-8, which describe

the individual fax modes. These sections also specify the ITU-

compatible field values (image parameters) for each mode.

The full set of permitted fields of TIFF for facsimile are included

in the current TIFF specification, Section 2 of this document and the

sections on specific modes of facsimile operation. This document

defines profiles of TIFF for facsimile, where a profile is a subset

of the full set of permitted fields and field values of TIFF for

facsimile.

Section 3 defines the minimal black-and-white facsimile mode (Profile

S), which is required in all implementations. Section 4 defines the

extended black-and-white fax mode (Profile F), which provides a

standard definition of TIFF-F. Section 5 describes the lossless

black-and-white mode using JBIG compression (Profile J). Section 6

defines the base color mode, required in all color implementations,

for the lossy JPEG representation of color and grayscale facsimile

data (Profile C). Section 7 defines the lossless JBIG color and

grayscale facsimile mode (Profile L) and Section 8 defines the Mixed

Raster Content facsimile mode (Profile M). Each of these sections

concludes with a table summarizing the required and recommended

fields for each mode and the values they can have.

Section 9 describes the MIME content type image/tiff and the use of

the optional Application parameter in connection with TIFF for

facsimile. Sections 10, 11, 12 and 13 give Security Considerations,

the ISOC Copyright Notice, References and Authors' Addresses. Annex A

gives a summary of the TIFF fields used or defined in this document

and provides a convenient reference for implementors.

To implement only the minimal interchange black-and-white set of

fields and values (Profile S), one need read only Sections 1, 2, 3, 9

and 10.

The following tree diagram shows the relationship among profiles and

between profiles and coding methods.

S (MH)

/ B&W / \ Color

------------ ----------

/ \ / F (MMR, MR) C (JPEG)

/ / J (JBIG) ---- / L (JBIG) M (MRC)

A profile is based on a collection of ITU-T facsimile coding methods.

For example, Profile S, the minimal mode, is based on Modified

Huffman (MH) compression, which are defined in ITU-T Rec. T.4.

Profile F specifies Modified Read (MR) and Modified Modified Read

(MMR) compressions, which are defined in ITU-T Rec. T.4 and T.6.

All implementations of TIFF for facsimile MUST implement Profile S,

which is the root node of the tree. All color implementations of TIFF

for facsimile MUST implement Profile C. The implementation of a

particular profile MUST also implement those profiles on the path

that connect it to the root node, and MAY optionally implement

profiles not on the path connecting it to the root node. For example,

an implementation of Profile M must also implement Profiles C and S,

and may optionally implement Profile F, J or L. For another example,

an implementation of Profile C must also implement Profile S, and may

optionally implement Profile F or J.

The key Words "MUST", "MUST NOT", "REQUIRED", "SHALL", " NOT",

"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

document are to be interpreted as described in [REQ].

2. TIFF and Fax

2.1. TIFF Overview

TIFF provides a means for describing, storing and interchanging

raster image data. A primary goal of TIFF is to provide a rich

environment within which applications can exchange image data. The

current TIFF specification [TIFF] defines a commonly used, core set

of TIFF fields known as Baseline TIFF. The current specification and

TIFF Technical Notes 1 and 2 [TTN1, TTN2] define several TIFF

extensions. The TIFF- based specification for fax applications uses a

subset of Baseline TIFF fields, with selected extensions, as

described in this document. In a few cases, this document defines new

TIFF fields specifically for fax applications.

2.1.1. File Structure

TIFF is designed for raster images, which makes it a good match for

facsimile documents, which are multi-page raster images. Each raster

image consists of a number of rows or scanlines, each of which has

the same number of pixels, the unit of sampling. Each pixel has at

least one sample or component (exactly one for black-and-white

images).

A TIFF file begins with an 8-byte image file header. The first two

bytes describe the byte order used within the file. Legal values are

"II" (0x4949) when bytes are ordered from least to most significant

(little- endian), and "MM" (0x4D4D), when bytes are ordered from most

to least significant (big-endian) within a 16- or 32-bit integer.

Either byte order can be used, except in the case of the minimal

black-and-white mode, which SHALL use value "II". The next two bytes

contain the value 42 that identifies the file as a TIFF file and is

ordered according to the value in the first two bytes of the header.

The last four bytes give the offset that points to the first image

file Directory (IFD). This and all other offsets in a TIFF file are

with respect to the beginning of the TIFF file. An IFD can be at any

location in the file after the header but must begin on a word

boundary.

An IFD is a sequence of tagged fields, sorted in ascending order by

tag value. An IFD consists of a 2-byte count of the number of fields,

a sequence of field entries and a 4-byte offset to the next IFD. The

fields contain information about the image and pointers to the image

data. Each separate raster image in the file is represented by an

IFD.

Each field entry in an IFD has 12 bytes and consists of a 2-byte Tag,

2 bytes identifying the field type (e.g. short, long, rational,

ASCII), 4 bytes giving the count (number of values or offsets), and 4

bytes that either contain the offset to a field value stored outside

the IFD, or, based on the type and count, the field value itself.

Resolution and metadata such as dates, names and descriptions are

examples of "long" field values that do not fit in 4 bytes and

therefore use offsets in the field entry. Details are given in the

TIFF specification [TIFF].

A TIFF file can contain more than one IFD, where each IFD is a

subfile whose type is given in the NewSubfileType field. Multiple

IFDs can be organized either as a linked list, with the last entry in

each IFD pointing to the next IFD (the pointer in the last IFD is 0),

or as a tree, using the SubIFDs field in the primary IFD [TTN1]. The

SubIFDs field contains an array of pointers to child IFDs of the

primary IFD.

Child IFDs describe related images, such as reduced resolution

versions of the primary IFD image. The same IFD can point both to a

next IFD and to child IFDs, and child IFDs can themselves point to

other IFDs.

All fax modes represent a multi-page fax image as a linked list of

IFDs, with a NewSubfileType field containing a bit that identifies

the IFD as one page of a multi-page document. Each IFD has a

PageNumber field, identifying the page number in ascending order,

starting at 0 for the first page. While a Baseline TIFF reader is not

required to read any IFDs beyond the first, an implementation that

reads the files that comply with this specification SHALL read

multiple IFDs. Only the Mixed Raster Content fax mode, described in

Section 8, requires the use of child IFDs.

The following figure illustrates the structure of a multi-page TIFF

file.

+-----------------------+

Header ------------+

+-----------------------+ First IFD

IFD (page 0) <-----------+ Offset

+--- ------------+

Value +-----------------------+

Offset +--> Long Values --+

+----------------------- Strip

Image Data <-+ Offset

strip 1 page 0

+-----------------------+

: :

+-----------------------+ Next IFD

IFD (page 1) <-----------+ Offset

+--- ------------+

Value +-----------------------+

Offset +--> Long Values --+

+----------------------- Strip

Image Data <-+ Offset

strip 1 page 1

+-----------------------+

strip 2 page 1 <-+

+-----------------------+

: :

+-----------------------+ Next IFD

IFD (page 2) <-----------+ Offset

:

2.1.2 Image Structure

An IFD stores an image as one or more strips, as shown in the

preceding figure. A strip consists of 1 or more scanlines (rows) of

raster image data in compressed form. An image may be stored in a

single strip or may be divided into several strips, which would

require less memory to buffer. (Baseline TIFF recommends about 8k

bytes per strip, but existing fax usage is typically one strip per

image.)

Each IFD requires three strip-related fields: StripOffsets,

RowsPerStrip and StripByteCounts. The StripOffsets field is an array

of pointers to the strip or strips that contain the actual image

data. The StripByteCounts field gives the number of bytes in each

strip after compression. TIFF requires that each strip, except the

last, contain the same number of scanlines, which is given in the

RowsPerStrip field. This document introduces the new StripRowCounts

field that allows a variable number of scanlines per strip, which is

required by the Mixed Raster Content fax mode (Section 8).

Image data is stored as uninterpreted, compressed image data streams

within a strip. The formats of these streams follow the ITU-T

Recommendations. The Compression field in the IFD indicates the type

of compression, and other TIFF fields in the IFD describe image

attributes, such as color encoding and spatial resolution.

Compression parameters are stored in the compressed data stream,

rather than in TIFF fields. This makes the TIFF representation and

compressed data format specification independent of each another.

This approach, modeled on [TTN2], allows TIFF to gracefully add new

compression schemes as they become available.

Some attributes can be specified both in the compressed data stream

and within a TIFF field. It is possible that the two values will

differ. When this happens for values required to interpret the data

stream, then the values in the data stream take precedence. For

informational values that are not required to interpret the data

stream, such as author name, then the TIFF field value takes

precedence.

2.1.3 TIFF File Structure for Fax Applications

The TIFF specification has a very flexible file structure, which does

not specify the ordering of IFDs, field values and image data in a

file. Individual applications may require or recommend an ordering.

This specification recommends that when using a TIFF file for

facsimile, A multi-page fax document SHOULD be represented as a

linked list of IFDs. It also recommends that a TIFF file for

facsimile SHOULD order pages in a TIFF file in the same way that they

are ordered in a fax data stream. In a TIFF file, a page consists of

several elements: one or more IFDs (including subIFDs), long field

values that are stored outside the IFDs, and image data (in one or

more strips).

The minimal black-and-white mode (Profile S) specifies a required

ordering of pages and elements within a page (Section 3.5). The

extended black-and-white mode (Profile F) provides guidelines for

ordering pages and page elements (Section 4.4.6). Other profiles

SHOULD follow these guidelines. This recommendation is intended to

simplify the implementation of TIFF writers and readers in fax

applications and the conversion between TIFF file and fax data stream

representations. However, for interchange robustness, 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.

This specification introduces an optional new GlobalParametersIFD

field, defined in Section 2.2.4. This field has type IFD and

indicates parameters describing the fax session. While it is often

possible to oBTain these parameters by scanning the file, it is

convenient to make them available together in one place for fast and

easy Access. If the GlobalParametersIFD occurs in a TIFF file, it

SHOULD be located in the first IFD, immediately following the 8-byte

image file header.

2.2 TIFF Fields for All Fax Applications

The TIFF specification [TIFF] is organized as a baseline set and

several extensions, including technical notes [TTN1, TTN2] that will

be incorporated in the next release of TIFF. The baseline and

extensions have required and optional fields.

Facsimile applications require (and recommend) a mixture of baseline

and extensions fields, as well as some new fields that are not part

of the TIFF specification and that are defined in this document. This

sub- section lists the fields that are required or recommended for

all modes. In particular, Section 2.2.1 lists the fields that are

required by all modes and that have values that do not depend on the

mode. Section 2.2.2 lists the fields that are required by all modes

and that have values which do depend on the mode. Section 2.2.3 lists

the fields that are recommended for all modes. Fields that are

required or recommended by some but not all modes are given in the

section (Section 3-8) that describes that mode. The sections for each

fax mode have sub-sections for required and recommended fields; each

sub-section organizes the fields according to whether they are

baseline, extension or new.

The fields required for facsimile have only a few legal values,

specified in the ITU-T Recommendations. Of these legal values, some

are required and some are optional, just as they are required

(mandatory) or optional in fax implementations that conform to the

ITU-T Recommendations. The required and optional values are noted in

the sections on the different fax modes.

This section describes the fields required or recommended by all fax

modes. The pattern for the description of TIFF fields in this draft

is:

FieldName(TagValueInDecimal) = allowable values. TYPE

WhetherRequiredByTIFForTIFFforFAX

Count = (omitted if =1) = (if not in current spec but available)

Explanation of the field, how it's used, and the values it can have.

Default value, if any, as specified in [TIFF]

When a field's default value is the desired value, that field may be

omitted from the relevant IFD unless specifically required by the

text of this specification.

2.2.1. TIFF fields required for all fax modes

The TIFF fields listed in this section SHALL be used by all fax

modes, but have field values that are not specified by the ITU

standards, i.e. the fields do not depend on the mode. The next sub-

section lists the fields that SHALL be used by all fax modes, but

which do have values specified by the ITU-specified or mode-specific

values. Fields that SHALL be used by some but not all modes are given

in the sections (3-8) which describe the modes that uses them.

ImageLength(257) SHORT or LONG

RequiredByTIFFBaseline

Total number of scanlines in image.

No default, must be specified.

PageNumber(297) SHORT

RequiredByTIFFforFAX, TIFFExtension

Count = 2

The first number represents the page number (0 for the first page);

the second number is the total number of pages in the document. If

the second value is 0, then the total page count is not available.

No default, must be specified

RowsPerStrip(278) SHORT or LONG

RequiredByTIFFBaseline

The number of scanlines per TIFF strip, except for the last strip.

For a single strip image, this is the same as the value of the

ImageLength field.

Default = 2**32 - 1 (meaning all scanlines in one strip)

StripByteCounts(279) SHORT or LONG

RequiredByTIFFBaseline

Count = number of strips

For each strip, the number of bytes in that strip after compression.

No default, must be specified.

StripOffsets(273) SHORT or LONG

RequiredByTIFFBaseline

Count = number of strips

For each strip, the byte offset from the beginning of the file to

the start of that strip.

No default, must be specified.

2.2.2 Additional TIFF fields required for all fax modes

The TIFF fields listed in this section SHALL be used by all fax

modes, but the values associated with them depend on the mode being

described and the associated ITU Recommendations. Therefore, only the

fields are defined here; the values applicable to a particular fax

mode are described in Sections 3-8. Fields that SHALL be used by some

but not all modes are given in the section (3-8) describing the mode

that uses them.

BitsPerSample(258) SHORT

RequiredByTIFFBaseline

Number of bits per image sample

Default = 1 (field may be omitted if this is the value)

Compression(259) SHORT

RequiredByTIFFBaseline

Compression method used for image data

Default = 1 (no compression, so may not be omitted for FAX)

FillOrder(266) SHORT

RequiredByTIFFforFax

The default bit order in Baseline TIFF per [TIFF] is indicated by

FillOrder=1, where bits are not reversed before being stored.

However, TIFF for Fax 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).

Default = 1 (field may be omitted if this is the value)

Facsimile data appears on the phone line in bit-reversed order

relative to its description in the relevant ITU compression

Recommendation. Therefore, a wide majority of facsimile

implementations choose this natural order for storage. Nevertheless,

all readers conforming to this specification must be able to read

data in both bit orders.

ImageWidth(256) SHORT or LONG

RequiredByTIFFBaseline

The number of pixels (columns) per scanline (row) of the image

No default, must be specified.

NewSubFileType(254) LONG

RequiredByTIFFforFAX

A general indication of the kind of data contained in this IFD

Bit 1 is 1 if the image is a single page of a multi-page document.

Default = 0 (no subfile bits on, so may not be omitted for FAX)

PhotometricInterpretation(262) SHORT

RequiredByTIFFBaseline

The color space of the image data

No default, must be specified

ResolutionUnit(296) SHORT

RequiredByTIFFBaseline

The unit of measure for resolution. 2 = inch, 3 = centimeter;

Default = 2 (field may be omitted if this is the value)

SamplesPerPixel(277) SHORT

RequiredByTIFFBaseline

The number of color components per pixel; SamplesPerPixel is 1 for a

black-and-white, grayscale or indexed (palette) image.

Default =1 (field may be omitted if this is the value)

XResolution(282) RATIONAL

RequiredByTIFFBaseline

The horizontal resolution of the image in pixels per resolution

unit. The ITU-T Recommendations for facsimile specify a small number

of horizontal resolutions: 100, 200, 300, 400 pixels per inch, and

80, 160 pixels per centimeter (or 204, 408 pixels per inch). The

allowed XResolution values for each mode are given in the section

defining that mode. Per [T.4], it is permissible for applications to

treat the following XResolution values as being equivalent: <204,

200> and <400,408> in pixels/inch. These equivalencies were allowed

by [T.4] to permit conversions between inch and metric based

facsimile terminals.

TIFF for Facsimile Writers SHOULD express XResolution in inch based

units, for consistency with historical practice and to maximize

interoperability. See the table below for information on how to

convert from an ITU-T metric value to its inch based equivalent

resolution.

No default, must be specified

YResolution(283) RATIONAL

RequiredByTIFFBaseline

The vertical resolution of the image in pixels per resolution unit.

The ITU-T Recommendations for facsimile specify a small number of

vertical resolutions: 100, 200, 300, 400 pixels per inch, and 38.5,

77, 154 pixels per centimeter (or 98, 196, 391 pixels per inch). The

allowed YResolution values for each mode are given in the section

defining that mode. Per [T.4], it is permissible for applications to

treat the following YResolution values as being equivalent: <98,

100>, <196, 200>, and <391, 400> in pixels/inch. These equivalencies

were allowed by [T.4] to permit conversions between inch and metric

based facsimile terminals. TIFF for Facsimile Writers SHOULD express

YResolution in inch based units, for consistency with historical

practice and to maximize interoperability. See the table below for

information on how to convert from an ITU-T metric value to its inch

based equivalent resolution. No default, must be specified

+-----------------------------+-----------------------------+

XResolution YResolution

+--------------+--------------+--------------+--------------+

ResolutionUnitResolutionUnitResolutionUnitResolutionUnit

=2 (inch) =3 (cm) =2 (inch) =3 (cm)

+--------------+--------------+--------------+--------------+

100 100

+--------------+--------------+--------------+--------------+

204 80 98 38.5

200 100

+--------------+--------------+--------------+--------------+

204 80 196 77

200 200

+--------------+--------------+--------------+--------------+

204 80 391 154

+--------------+--------------+--------------+--------------+

300 300

+--------------+--------------+--------------+--------------+

408 160 391 154

400 400

+--------------+--------------+--------------+--------------+

2.2.3 TIFF fields recommended for all fax modes

The TIFF fields listed in this section MAY be used by all fax modes.

However, Profile S writers (the minimal fax mode described in Section

3) SHOULD NOT use these fields. Recommended fields that are mode-

specific are described in Sections 3-8.

DateTime(306) ASCII

OptionalInTIFFBaseline

Date/time of image creation in 24-hour format "YYYY:MM:DD HH:MM:SS".

No default.

DocumentName(269) ASCII

OptionalInTIFFExtension(DocumentStorageAndRetrieval)

The name of the scanned document. This is a TIFF extension field,

not a Baseline TIFF field.

No default.

ImageDescription(270) ASCII

OptionalInTIFFBaseline

A string describing the contents of the image.

No default.

Orientation(274) = 1-8. SHORT

OptionalinTIFFBaseline

1: 0th row represents the visual top of the image; the 0th column

represents the visual left side of the image. See the current TIFF

spec [TIFF] for further values; Baseline TIFF only requires value=1.

Default = 1.

Note: It is recommended that a writer that is aware of the

orientation will include this field to give a positive indication of

the orientation, even if the value is the default. If the

Orientation field is omitted, the reader SHALL assume a value of 1.

Software(305) ASCII

OptionalInTIFFBaseline

The optional name and release number of the software package that

created the image.

No default.

2.2.4 New TIFF fields recommended for fax modes

The new TIFF fields listed in this section MAY be used by all fax

modes, but their support is not expected for the minimal fax mode

described in Section 3. In addition, support for these new TIFF

fields has not been included in historical TIFF-F readers described

in Section 4 and [TIFF- F]. These fields describe "global" parameters

of the fax session that created the image data. They are optional,

not part of the current TIFF specification, and are defined in this

document.

The first new field, GlobalParametersIFD, is an IFD that contains

global parameters and is located in a Primary IFD.

GlobalParametersIFD (400) IFD

An IFD containing global parameters. It is recommended that a TIFF

writer place this field in the first IFD, where a TIFF reader would

find it quickly.

Each field in the GlobalParametersIFD is a TIFF field that is legal

in any IFD. Required baseline fields should not be located in the

GlobalParametersIFD, but should be in each image IFD. If a conflict

exists between fields in the GlobalParametersIFD and in the image

IFDs, then the data in the image IFD shall prevail.

Among the GlobalParametersIFD entries is a new ProfileType field

which generally describes information in this IFD and in the TIFF

file.

ProfileType(401) LONG

The type of image data stored in this IFD.

0 = Unspecified

1 = Group 3 fax

No default

The following new global fields are defined in this document as IFD

entries for use with fax applications.

FaxProfile(402) = 0 - 6. BYTE

The profile that applies to this file; a profile is subset of the

full set of permitted fields and field values of TIFF for facsimile.

The currently defined values are:

0: does not conform to a profile defined for TIFF for facsimile

1: minimal black & white lossless, Profile S

2: extended black & white lossless, Profile F

3: lossless JBIG black & white, Profile J

4: lossy color and grayscale, Profile C

5: lossless color and grayscale, Profile L

6: Mixed Raster Content, Profile M

CodingMethods(403) LONG

This field indicates which coding methods are used in the file. A

bit value of 1 indicates which of the following coding methods is

used:

Bit 0: unspecified compression,

Bit 1: 1-dimensional coding, ITU-T Rec. T.4 (MH - Modified Huffman),

Bit 2: 2-dimensional coding, ITU-T Rec. T.4 (MR - Modified Read),

Bit 3: 2-dimensional coding, ITU-T Rec. T.6 (MMR - Modified MR),

Bit 4: ITU-T Rec. T.82 coding, using ITU-T Rec. T.85 (JBIG),

Bit 5: ITU-T Rec. T.81 (Baseline JPEG),

Bit 6: ITU-T Rec. T.82 coding, using ITU-T Rec. T.43 (JBIG color),

Bits 7-31: reserved for future use

Note: There is a limit of 32 compression types to identify standard

compression methods.

VersionYear(404) BYTE

Count: 4

The year of the standard specified by the FaxProfile field, given as

4 characters, e.g. '1997'; used in lossy and lossless color modes.

ModeNumber (405) BYTE

The mode of the standard specified by the FaxProfile field. A

value of 0 indicates Mode 1.0; used in Mixed Raster Content mode.

3. Minimal Black-and-White Fax Mode

This section defines the minimal black-and-white subset of TIFF for

facsimile. This subset is designated Profile S. All implementations

of TIFF for facsimile SHALL support the minimal subset.

Black-and-white mode is the binary fax application most users are

familiar with today. This mode is appropriate for black-and-white

text and line art. Black-and-white mode is divided into two levels of

capability. This section describes the minimal interchange set of

TIFF fields that must be supported by all implementations in order to

assure that some form of image, albeit black-and-white, can be

interchanged. This minimum interchange set is a strict subset of the

fields and values defined for the extended black-and-white mode

(TIFF-F or Profile F) in Section 4, which describes extensions to the

minimal interchange set of fields that provide a richer set of

black-and-white capabilities.

3.1. Overview

The minimal interchange portion of the black-and-white facsimile mode

supports 1-dimensional Modified Huffman (MH) compression, with the

original Group 3 fax resolutions, commonly called "standard" and

"fine."

To assure interchange, this mode uses the minimal set of fields, with

a minimal set of values. There are no recommended fields in this

mode. Further, the TIFF file is required to be "little endian," which

means that the byte order value in the TIFF header is "II". This mode

defines a required ordering for the pages in a fax document and for

the IFDs and image data of a page. It also requires that a single

strip contain the image data for each page; see Section 3.5. The

image data may contain RTC sequences, as specified in Section 3.4.

3.2. Required TIFF Fields

Besides the fields listed in Section 2.2.1, the minimal black-and-

white fax mode requires the following fields. The fields listed in

Section 2.2.1 and the fields and fax-specific values specified in

this sub- section must be supported by all implementations.

3.2.1 Baseline fields

BitsPerSample(258) = 1. SHORT

RequiredByTIFFBaseline

Binary data only.

Default = 1 (field may be omitted if this is the value)

Compression(259) = 3. SHORT

RequiredByTIFFBaseline

3 = 1- or 2- dimensional coding.

The value 3 is a TIFF extension value [TIFF]. The T4Options field

must be specified and its value specifies that the data is encoded

using the Modified Huffman (MH) encoding of [T.4].

FillOrder(266) = 2. SHORT

RequiredByTIFFBaseline

2 = Least Significant Bit first

NOTE: Baseline TIFF readers are only required to support FillOrder =

1, where the lowest numbered pixel is stored in the MSB of the byte.

However, because many devices, such as modems, transmit the LSB first

when converting the data to serial form, it is common for black-and-

white fax products to use the second FillOrder =2, where the lowest

numbered pixel is stored in the LSB. Therefore, this value is

specified in the minimal black-and-white mode.

ImageWidth(256) = 1728. SHORT or LONG

RequiredByTIFFBaseline

This mode only supports a page width of 1728 pixels. This width

corresponds to North American Letter and Legal and to ISO A4 size

pages.

No default, must be specified.

NewSubFileType(254) = (Bit 1=1). LONG

RequiredByTIFFforFAX

Bit 1 is 1 if the image is a single page of a multi-page document.

Default = 0 (no subfile bits on, so may not be omitted for fax)

PhotometricInterpretation(262) = 0. SHORT

RequiredByTIFFBaseline

0 = pixel value 1 means black

No default, must be specified

ResolutionUnit(296) = 2. SHORT

RequiredByTIFFBaseline

The unit of measure for resolution. 2 = inch.

Default = 2 (field may be omitted if this is the value)

SamplesPerPixel(277) = 1. SHORT

RequiredByTIFFBaseline

The number of components per pixel; 1 for black-and-white

Default =1 (field may be omitted if this is the value)

XResolution(282) = 200, 204. RATIONAL

RequiredByTIFFBaseline

The horizontal resolution of the image is expressed in pixels per

resolution unit. In pixels/inch, the allowed values are 200 and 204,

which may be treated as equivalent. See Section 2.2.2 for inch-

metric equivalency.

No default, must be specified

YResolution(283) = 98, 100, 196, 200. RATIONAL

RequiredByTIFFBaseline

The vertical resolution of the image is expressed in pixels per

resolution unit. In pixels/inch, the allowed values are 98, 100,

196 and 200; 98 and 100 may be treated as equivalent, and 196 and

200 may be treated as equivalent. See Section 2.2.2 for inch-metric

equivalency.

No default, must be specified

3.2.2 Extension fields

T4Options(292) = (Bit 0 = 0, Bit 1 = 0, Bit 2 = 0, 1) LONG

RequiredTIFFExtension (when Compression = 3)

Bit 0 = 0 indicates MH encoding.

Bit 1 must be 0

Bit 2 = 1 indicates that EOLs are byte aligned, = 0 EOLs not byte

aligned

Default is all bits are 0 (applies when EOLs are not byte aligned)

Note: The T4Options field is required when the Compression field has

a value of 3. Bit 0 of this field specifies the encoding used (MH

only in this mode) and Bit 2 indicates whether the EOL codes are

byte-aligned or not. If they are byte aligned, then fill bits have

been added as necessary so that the End of Line (EOL) codes always

end on byte boundaries. See Section 3.4 for details.

3.2.3. New Fields

None.

3.3. Recommended TIFF Fields

None.

3.4. End of Line (EOL) and Return to Control (RTC)

The handling of End of Line (EOL) codes and Return to Control (RTC)

sequences illustrate the differences between conventional fax, which

is bit and stream oriented, and TIFF, which is byte and file

oriented. Conventional fax, Baseline TIFF and TIFF extensions for fax

all handle EOLs and RTCs differently.

In conventional fax, an MH-compressed fax data stream for a page

consists of the following sequence:

EOL, compressed data (first line), EOL, compressed data, ... ,

EOL, compressed data (last line), RTC (6 consecutive EOL codes)

Baseline TIFF does not use EOL codes or Return to Control (RTC)

sequences for MH-compressed data. However, the TIFF extension field

T4Options used in this specification for MH compression (Compression

= 3) requires EOLs.

Furthermore, Bit 2 in the T4Options field indicates whether or not

the EOL codes are byte aligned. If Bit 2 = 1, indicating the EOL

codes are byte aligned, then fill bits have been added as necessary

before EOL codes so that an EOL code always ends on a byte boundary,

and the first bit of data following an EOL begins on a byte boundary.

Without fill bits, an EOL code may end in the middle of a byte. 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). Not all TIFF readers

historically used for fax are able to deal with non-byte aligned

data.

While TIFF extension requires EOL codes, TIFF in fax applications has

traditionally prohibited RTC sequences. Implementations that want

common processing and interfaces for fax data streams and Internet

fax files would prefer that the TIFF data include RTC sequences.

To reconcile these differences, RTCs are allowed in cases where EOL

codes are not byte aligned and no fill bits have been added to the

data. This corresponds to situations where the fax data is simply

inserted in a strip without being processed or interpreted. RTCs

should not occur in the data when EOLs have been byte aligned. This

is formally specified in the next sub-section.

3.4.1. RTC Exclusion

Implementations which wish to maintain strict conformance with TIFF

and compatibility with the historical use of TIFF for fax SHOULD NOT

include the RTC sequence when writing TIFF files. However,

implementations which need to support "transparency" of T.4-generated

image data MAY include RTCs when writing TIFF files if the flag

settings of the T4Options field are set for non-byte aligned data,

i.e. Bit 2 is 0. Implementors of TIFF readers should be aware that

there are some existing TIFF implementations for fax that include the

RTC sequence in MH image data. Therefore, minimal set readers MUST be

able to process files which do not include RTCs and SHOULD be able to

process files which do include RTCs.

3.5. File Structure

The TIFF header, described in Section 2.1.1, contains two bytes which

describe the byte order used within the file. For the minimal black-

and- white mode, these bytes SHALL have the value "II" (0x4949),

denoting that the bytes in the TIFF file are in LSByte-first order

(little- endian). The first or 0th IFD immediately follows the

header, so that offset to the first IFD is 8. The headers values are

shown in the following table:

+--------+-------------------+--------+-----------+

Offset Description Value

+--------+-------------------+--------+-----------+

0 Byte Order 0x4949 (II)

+--------+-------------------+--------+-----------+

2 Identifier 42 decimal

+--------+-------------------+--------+-----------+

4 Offset of 0th IFD 0x 0000 0008

+--------+-------------------+--------+-----------+

The minimal black-and-white mode SHALL order IFDs and image data

within a file as follows: 1) there SHALL be an IFD for each page in a

multi- page fax document; (2) the IFDs SHALL occur in the same order

in the file as the pages occur in the document; (3) the IFD SHALL

precede the image data to which it has offsets; (4) the image data

SHALL occur in the same order in the file as the pages occur in the

document; (5) the IFD, the value data and the image data it has

offsets to SHALL precede the next image IFD; and (6) the image data

for each page SHALL be contained within a single strip.

As a result of (6), the StripOffsets field will contain the pointer

to the image data. With two exceptions, the field entries in the IFD

contain the field values instead of offsets to field values located

outside the IFD. The two exceptions are the values for the

XResolution and YResolution fields, both of which are type RATIONAL

and require 2 4- byte numbers. These "long" field values SHALL be

placed immediately after the IFD which contains the offsets to them,

and before the image data pointed to by that IFD.

The effect of these requirements is that the IFD for the first page

SHALL come first in the file after the TIFF header, followed by the

long field values for XResolution and YResolution, followed by the

image data for the first page, then the IFD for second page, etc.

This is shown in the following figure. Each IFD is required to have a

PageNumber field, which has value 0 for the first page, 1 for the

second page, and so on.

+-----------------------+

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

+-----------------------+

:

Using this file structure may reduce the memory requirements in

implementations. It is also provides some support for streaming, in

which a file can be processed as it is received and before the entire

file is received.

3.6 Minimal Black-and-white Mode Summary

The table below summarizes the TIFF fields that comprise the minimal

interchange set for black-and-white facsimile. The Baseline and

Extension fields and field values MUST be supported by all

implementations. For convenience in the table, certain fields which

have a value that is a sequence of flag bits are shown taking integer

values that correspond to the flags that are set. An implementation

should test the setting of the relevant flag bits individually,

however, to allow extensions to the sequence of flag bits to be

appropriately ignored. (See, for example, T4Options below.)

+---------------------------+--------------------------------+

Baseline Fields Values

+---------------------------+--------------------------------+

BitsPerSample 1

+---------------------------+--------------------------------+

Compression 3: 1D Modified Huffman coding

set T4Options = 0 or 4

+------------------------------------------------------------+

+---------------------------+--------------------------------+

FillOrder 2: least significant bit first

+---------------------------+--------------------------------+

ImageWidth 1728

+---------------------------+--------------------------------+

ImageLength n: total number of scanlines

in image

+---------------------------+--------------------------------+

NewSubFileType 2: Bit 1 identifies single

page of a multi-page document

+---------------------------+--------------------------------+

PageNumber n,m: page number n followed by

total page count m

+---------------------------+--------------------------------+

PhotometricInterpretation 0: pixel value 1 means black

+---------------------------+--------------------------------+

ResolutionUnit 2: inch

+---------------------------+--------------------------------+

RowsPerStrip number of scanlines per strip

= ImageLength, with one strip

+---------------------------+--------------------------------+

SamplesPerPixel 1

+---------------------------+--------------------------------+

StripByteCounts number of bytes in TIFF strip

+---------------------------+--------------------------------+

StripOffsets offset from beginning of

file to single TIFF strip

+---------------------------+--------------------------------+

XResolution 204, 200 (pixels/inch)

+---------------------------+--------------------------------+

YResolution 98, 196, 100, 200 (pixels/inch)

+---------------------------+--------------------------------+

Extension Fields

+---------------------------+--------------------------------+

T4Options 0: MH coding, EOLs not byte

aligned

4: MH coding, EOLs byte aligned

+---------------------------+--------------------------------+

4. Extended Black-and-White fax mode

This section defines the extended black-and-white mode or Profile F

of TIFF for facsimile. It provides a standard definition of what has

historically been known as TIFF Class F and now TIFF-F. In doing so,

it aligns this mode with current ITU-T Recommendations for black-

and-white fax and with existing industry practice. Implementations of

this profile include implementations of Profile S.

This section describes extensions to the minimal interchange set of

fields (Profile S) that provide a richer set of black-and-white

capabilities. The fields and values described in this section are a

superset of the fields and values defined for the minimal interchange

set in Section 3. In addition to the MH encoding, Modified READ (MR)

and Modified Modified READ (MMR) encoding as described in [T.4] and

[T.6] are supported.

Section 4.1 gives an overview of TIFF-F. Section 4.2 describes the

TIFF fields that SHALL be used in this mode. Section 4.3 describes

the fields that MAY be used in this mode. In the spirit of the

original TIFF-F specification, Sections 4.4 and 4.5 discuss technical

implementation issues and warnings. Section 4.6 gives an example use

of TIFF-F. Section 4.7 gives a summary of the required and

recommended fields and their values.

4.1 TIFF-F Overview

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 serves as the formal

definition of the F application of [TIFF] for Internet applications.

For ease of reference, the term TIFF-F will be used throughout this

document as a shorthand for the extended black-and-white mode or

profile of TIFF for facsimile.

Up until the TIFF 6.0 specification, TIFF supported various "Classes"

which defined the use of TIFF for various applications. Classes were

used to support specific applications. In this spirit, TIFF-F has

been known historically as "TIFF Class F". Previous informal TIFF-F

documents [TIFF-F0] 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

adding the TIFF extensions to 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 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.

4.2. Required TIFF Fields

This section lists the required fields and the values they must have

to be ITU-compatible. Besides the fields listed in Section 2.2.1, the

extended black-and-white fax mode SHALL use the following fields.

4.2.1. Baseline fields

BitsPerSample(258) = 1. SHORT

RequiredByTIFFBaseline

Binary data only.

Default = 1 (field may be omitted if this is the value)

Compression(259) = 3, 4. SHORT

RequiredByTIFFBaseline

3 = 1- or 2- dimensional coding, must have T4Options field This is

a TIFF Extension value [TIFF].

4 = 2-dimensional coding, ITU-T Rec. T.6 (MMR - Modified Modified

Read, must have T6Options field)) This is a TIFF Extension value.

Default = 1 (and is not applicable; field must be specified)

NOTE: Baseline TIFF permits use of value 2 for Modified Huffman

encoding, but data is presented in a form which does not use EOLs,

and so TIFF for facsimile uses Compression=3 instead. See Sections

4.4.4, 4.5.1 and 4.5.2 for more information on compression and

encoding.

FillOrder(266) = 1 , 2. SHORT

RequiredByTIFFBaseline

Profile 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

ImageWidth(256) SHORT or LONG

RequiredByTIFFBaseline

This mode supports the following fixed page widths: 1728, 2592, 3456

(corresponding to North American Letter and Legal, ISO A4 paper

sizes), 2048, 3072, 4096 (corresponding to ISO B4 paper size), and

2432, 3648, 4864 (corresponding to ISO A3 paper size).

No default; must be specified

NOTE: 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 longer supported in

Group 3 facsimile, so the related width values are now obsolete. See

section 4.5.2 for more information on inch/metric equivalencies and

other implementation details.

NewSubFileType(254) = (Bit 1=1). LONG

RequiredByTIFFforFAX

Bit 1 is 1 if the image is a single page of a multi-page document.

Default = 0 (no subfile bits on, so may not be omitted for fax)

NOTE: Bit 1 is always set to 1 for TIFF-F, indicating a single page

of a multi-page image. The same bit settings are used when TIFF-F is

used for a one page fax image. See Section 4.4.3 for details on

multi-page files.

PhotometricInterpretation(262) = 0, 1. SHORT

RequiredByTIFFBaseline

0 = pixel value 1 means black, 1 = pixel value 1 means white.

This field allows notation of an inverted or negative image.

No default, must be specified

ResolutionUnit(296) = 2, 3. SHORT

RequiredByTIFFBaseline

The unit of measure for resolution. 2 = inch, 3 = centimeter; TIFF-F

has traditionally used inch-based measures.

Default = 2 (field may be omitted if this is the value)

SamplesPerPixel(277) = 1. SHORT

RequiredByTIFFBaseline

1 = monochrome, bilevel in this case (see BitsPerSample)

Default =1 (field may be omitted if this is the value)

XResolution(282) = 200, 204, 300, 400, 408 RATIONAL

RequiredByTIFFBaseline

The horizontal resolution of the image is expressed in pixels per

resolution unit. In pixels/inch, the allowed values are: 200, 204,

300, 400, and 408. See Section 2.2.2 for inch-metric equivalency.

No default, must be specified

NOTE: 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 80 pixels/cm, which is

equivalent to 204 pixels per inch. See section 4.5.2 for information

on implementation details.

YResolution(283) = 98, 100, 196, 200, 300, 391, and 400 RATIONAL

RequiredByTIFFBaseline

The vertical resolution of the image is expressed in pixels per

resolution unit. In pixels/inch, the allowed values are: 98, 100,

196, 200, 300, 391, and 400 pixels/inch.

See Section 2.2.2 for inch-metric equivalency.

No default, must be specified

NOTE: 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 and 38.5 (cm),

which are equivalent to 196 and 98 pixels per inch respectively. See

section 4.5.2 for more information on implementation details.

NOTE: Not all combinations of XResolution, YResolution and ImageWidth

are legal. The following table gives the legal combinations and

corresponding paper size [T.30].

+--------------+-----------------+---------------------------+

XResolution x YResolution ImageWidth

+--------------+-----------------+---------+--------+--------+

200x100, 204x98

200x200, 204x196 1728 2048 2432

204x391

+--------------+-----------------+---------+--------+--------+

300 x 300 2592 3072 3648

+--------------+-----------------+---------+--------+--------+

408 x 391, 400 x 400 3456 4096 4864

+--------------+-----------------+---------+--------+--------+

Letter,A4 B4 A3

Legal

+---------+--------+--------+

Paper Size

+---------------------------+

4.2.2. Extension fields

T4Options(292) = (Bit 0 = 0 or 1, Bit 1 = 0, Bit 2 = 0 or 1) LONG

RequiredTIFFExtension (when Compression = 3)

T4Options was also known as Group3Options in a prior version of

[TIFF].

Bit 0 = 1 indicates MR encoding, = 0 indicates MH encoding.

Bit 1 must be 0

Bit 2 = 1 indicates that EOLs are byte aligned, = 0 EOLs not byte

aligned

Default is all bits are 0 (applies when MH encoding is used and EOLs

are not byte aligned EOLs) (See Section 3.2.2.)

The T4Options field is required when the Compression field has a

value of 3. This field specifies the encoding used (MH or MR) and

whether the EOL codes are byte-aligned or not. If they are byte

aligned, then fill bits have been added as necessary so that the End

of Line (EOL) codes always end on byte boundaries See Sections 3.4,

4.5.3 and 4.5.4 for details.

T6Options(293) = (Bit 0 = 0, Bit 1 = 0). LONG

RequiredTIFFExtension (when Compression = 4)

Used to indicate parameterization of 2D Modified Modified Read

compression. T6Options was also known as Group4Options in a prior

version of [TIFF].

Bit 0 must be 0.

Bit 1 = 0 indicates uncompressed data mode is not allowed; = 1

indicates uncompressed data is allowed (see [TIFF]).

Default is all bits 0. For FAX, the field must be present and have

the value 0. The use of uncompressed data where compression would

expand the data size is not allowed for FAX.

NOTE: 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 4.5.6.

4.2.3. New fields

None.

4.3. Recommended TIFF fields

4.3.1. Baseline fields

See Section 2.2.3.

4.3.2. Extension fields

See Section 2.2.3.

4.3.3. New fields

Three new, optional fields, used in the original TIFF-F description

to describe page quality, are defined in this specification. The

information contained in these fields is usually obtained from

receiving facsimile hardware (if applicable). 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

applications 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

The number of "bad" scan lines encountered by the facsimile device

during reception. A "bad" scanline is defined as a scanline that,

when decoded, comprises an incorrect number of pixels. Note that

PercentBad = (BadFaxLines/ImageLength) * 100

No default.

CleanFaxData(327) = 0, 1, 2. SHORT

Indicates if "bad" lines encountered during reception are stored in

the data, or if "bad" lines have been replaced by the receiver.

0 = No "bad" lines

1 = "bad" lines exist, but were regenerated by the receiver,

2 = "bad" lines exist, but have not been regenerated.

No default.

NOTE: 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

Maximum number of consecutive "bad" scanlines received. The

BadFaxLines field indicates only the quantity of bad lines.

No Default.

NOTE: The BadFaxLines and ImageLength data indicate only the quantity

of bad lines. The ConsecutiveBadFaxLines field is an indicator of the

distribution of bad lines and may therefore be a better general

indicator of perceived image quality. See Section 4.4.5 for examples

of the use of these fields.

4.4. Technical Implementation Issues

4.4.1 Strips

In general, TIFF files divide an image into "strips," also known as

"bands." Each strip contains a few scanlines 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 number of scanlines in a strip is described by the RowsPerStrip

value and the number of bytes in the strip after compression by the

StripByteCount value. The location in the TIFF file of each strip is

given by the StripOffsets values.

Strip size is application dependent. The recommended approach for

multi- page TIFF-F images is to represent each page as a single

strip. Existing TIFF-F usage is typically one strip per page in

multi-page TIFF-F files. See Sections 2.1.2 and 2.1.3.

4.4.2 Bit Order

The current TIFF specification [TIFF] does not require a Baseline

TIFF reader to support FillOrder=2, i.e. lowest numbered 1-bit pixel

in the least significant bit of a byte. It further recommends that

FillOrder=2 be used only in special purpose applications.

Facsimile data appears on the phone line in bit-reversed order

relative to its description in ITU-T Recommendation T.4. Therefore,

a wide majority of facsimile applications choose this natural order

for data in a file. Nevertheless, TIFF-F readers must be able to read

data in both bit orders and support FillOrder values of 1 and 2.

4.4.3. Multi-Page

Many existing applications 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.

It is recommended that applications 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.

4.4.4. 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 [T.4] 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 ITU-T T.6

Recommendation [T.6]. MMR 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 supports these three compression methods. The most common

practice is the one-dimensional Modified Huffman (MH) compression

method. This is specified by setting the Compression field value to

3 and then setting bit 0 of the T4Options field to 0. Alternatively,

the two dimensional Modified READ (MR) method, which is much less

frequently used in historical TIFF-F implementations, may be selected

by setting bit 0 of the T4Options field to 1. The value of Bit 2 in

this field is determined by the use of fill bits.

Depending upon the application, the more efficient two-dimensional

Modified Modified Read (MMR)compression method from T.6 may be

selected by setting the Compression field value to 4 and then setting

the first two bits (and all unused bits) of the T6Options field to 0.

More information to aid the implementor in making a compression

selection is contained in Section 4.5.2.

Baseline TIFF also permits use of Compression=2 to specify Modified

Huffman compression, but the data does not use EOLs. As a result,

TIFF-F uses Compression=3 instead of Compression=2 to specify

Modified Huffman compression.

4.4.5. 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.

TIFF Writers SHOULD only generate these fields 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.

4.4.6. Practical Guidelines for Writing and 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.

The structure for a multi-page TIFF-F file will include one IFD per

page of the document. In this case, this IFD will define the

attributes for a single page. A second simplifying guideline is that

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, 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, another simplifying guideline 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 applications 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 applications which require the use of "streaming"

techniques (see section 4.4.7). In the event a different image strip

size guideline has been used (e.g. constant size for image strips

that may be less than the page size), this will immediately be

evident from the values/offsets of the fields that are related to

strips.

A third simplifying guideline is that each IFD SHOULD be placed in

the TIFF-F file structure at a point which precedes the image which

the IFD describes.

In addition, a fourth simplifying guideline 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.

If the image data is stored in multiple strips, then the strips

SHOULD occur in the file in the same order that the data they contain

occurs in the facsimile transmission, starting at the top of the

page.

TIFF-F writers MAY make a fifth simplifying guideline, in which the

IFD, the value data and the image data to which the IFD has offsets

precede the next image IFD. However, this guideline has been relaxed

(writers MAY rather than SHOULD use it) compared to the other

guidelines given here to reflect past practices for TIFF-F.

In the case of the minimal mode, which is also the minimal subset of

Profile S, the SHOULD's and MAY's of these guidelines become SHALL's

(see Section 3.5).

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).

4.4.7. Use of TIFF-F for Streaming Applications

TIFF-F has historically been used for handling fax image files in

applications 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,

assumptions may be required that differ from those provided in this

section (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.

4.5. Implementation Warnings

4.5.1 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.

4.5.2. 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, implementors 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.

Implementors 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 applications to treat the following

XResolution values as being equivalent: <204,200> and <400,408>. In

a similar respect, the following YResolution values 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 applications,

but this use is not recommended for the creation of TIFF-F files by a

writer.

4.5.3. 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, or Profile

S, as defined in Section 3 includes support for both byte-aligned and

non- byte-aligned EOLs; see Section 3.2.2.

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.

4.5.4. 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.

4.5.5. RTC Exclusion

Aside from EOLs, TIFF-F files have historically only contained image

data. This means that applications 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, applications which need to support "transparency" of [T.4]

image data MAY include RTCs 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.

4.5.6 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.

4.6. Example Use of TIFF-F

The Profile 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

tradi- tional voice message store-and-forward functions. 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.

4.7. Extended Black-and-white Fax Mode Summary

Recommended fields are shown with an asterisk *.

Required fields or values are shown with a double asterisk **. If the

double asterisk is on the field name, then all the listed values are

required of implementations; if the double asterisks are in the

Values column, then only the values suffixed with a double asterisk

are required of implementations.

+---------------------------+--------------------------------+

Baseline Fields Values

+---------------------------+--------------------------------+

BitsPerSample 1**

+---------------------------+--------------------------------+

Compression 3**: 1D Modified Huffman and

2D Modified Read coding

4: 2D Modified Modified Read

coding

+---------------------------+--------------------------------+

DateTime* {ASCII}: date/time in 24-hour

format "YYYY:MM:DD HH:MM:SS"

+---------------------------+--------------------------------+

FillOrder** 1: most significant bit first

2: least significant bit first

+------------------------------------------------------------+

+------------------------------------------------------------+

ImageDescription* {ASCII}: A string describing

the contents of the image.

+---------------------------+--------------------------------+

ImageWidth 1728**, 2048, 2432, 2592,

3072, 3456, 3648, 4096, 4864

+---------------------------+--------------------------------+

ImageLength** n: total number of scanlines

in image

+---------------------------+--------------------------------+

NewSubFileType 2**: Bit 1 identifies single

page of a multi-page document

+---------------------------+--------------------------------+

Orientation 1**-8, Default 1

+---------------------------+--------------------------------+

PhotometricInterpretation 0: pixel value 1 means black

** 1: pixel value 1 means white

+---------------------------+--------------------------------+

ResolutionUnit** 2: inch

3: centimeter

+---------------------------+--------------------------------+

RowsPerStrip** n: number of scanlines per

TIFF strip

+---------------------------+--------------------------------+

SamplesPerPixel 1**

+---------------------------+--------------------------------+

Software* {ASCII}: name & release

number of creator software

+---------------------------+--------------------------------+

StripByteCounts** <n>: number or bytes in TIFF

strip

+---------------------------+--------------------------------+

StripOffsets** <n>: offset from beginning of

file to each TIFF strip

+---------------------------+--------------------------------+

XResolution 200, 204**, 300, 400, 408

(written in pixels/inch)

+---------------------------+--------------------------------+

YResolution 98**, 196**, 100,

200, 300, 391, 400

(written in pixels/inch)

+---------------------------+--------------------------------+

Extension Fields

+---------------------------+--------------------------------+

+---------------------------+--------------------------------+

T4Options 0**: required if Compression

is Modified Huffman, EOLs are

not byte aligned

1: required if Compression is

2D Modified Read, EOLs are

not byte aligned

4**: required if Compression

is Modified Huffman, EOLs are

byte aligned

+---------------------------+--------------------------------+

T4Options (continued) 5: required if Compression

is 2D Modified Read, EOLs are

byte aligned

+---------------------------+--------------------------------+

T6Options 0: required if Compression is

2D Modified Modified Read

+---------------------------+--------------------------------+

DocumentName* {ASCII}: name of scanned

document

+---------------------------+--------------------------------+

PageNumber** n,m: page number followed by

total page count

+---------------------------+--------------------------------+

New Fields

+---------------------------+--------------------------------+

BadFaxLines* number of "bad" scanlines

encountered during reception

+---------------------------+--------------------------------+

CleanFaxData* 0: no "bad" lines

1: "bad" lines exist, but were

regenerated by receiver

2: "bad" lines exist, but have

not been regenerated

+---------------------------+--------------------------------+

ConsecutiveBadFaxLines* Max number of consecutive

"bad" lines received

+---------------------------+--------------------------------+

5. Lossless JBIG Black-and-White Fax Mode

This section defines the lossless JBIG black-and-white mode or

Profile J of TIFF for facsimile. Implementations of this profile are

required to also implement Profile S.

The previous section described the extended interchange set of TIFF

fields for black-and-white fax, which provided support for the MH, MR

and MMR compression of black-and-white images. This section adds a

mode with JBIG compression capability.

5.1. Overview

This section describes a black-and-white mode that uses JBIG

compression. The ITU-T has approved the single-progression sequential

mode of JBIG [T.82] for Group 3 facsimile. JBIG coding offers

improved compression for halftoned originals. JBIG compression is

used in accordance with the application rules given in ITU-T Rec.

T.85 [T.85].

This mode is essentially the extended black-and-white mode with JBIG

compression used instead of MH, MR or MMR.

5.2. Required TIFF Fields

This section lists the required fields and the values they must have

to be ITU-compatible. Besides the fields listed in Section 2.2.1, the

extended black-and-white fax mode requires the following fields.

5.2.1. Baseline fields

The TIFF fields that SHALL be used in this mode are the same as those

described in Section 4.2.1 for the extended black-and-white mode,

with two exceptions: the following text replaces the text in Section

4.2.1 for the Compression and FillOrder fields.

Compression(259) = 9. SHORT

RequiredByTIFFBaseline

9 = ITU-T Rec. T.82 coding, applying ITU-T Rec. T.85 (JBIG). This is

a TIFF extension value.

Default = 1 (and is not applicable; field must be specified).

FillOrder(266) = 2. SHORT

RequiredByTIFFBaseline

2 = Pixels are arranged within a byte such that pixels with lower

column values are stored in the lower-order bits of the bytes, i.e.,

least significant bit first (LSB).

NOTE: The JBIG coding of black-and-white image data in Profile J

follows ITU-T Rec. T.85 [T.85], which specifies LSB first ordering

within a byte. Note that Baseline TIFF readers are only required to

support MSB first ordering or FillOrder = 1.

5.2.2. Extension fields

Same fields as those in Section 2.2.1.

5.2.3. New fields

None.

5.3. Recommended TIFF Fields

See Section 2.2.3 and 2.2.4.

5.4. Lossless JBIG Black-and-white Fax Mode Summary

Recommended fields are shown with an asterisk *.

Required fields or values are shown with a double asterisk **. If the

double asterisk is on the field name, then all the listed values are

required of implementations; if the double asterisks are in the

Values column, then only the values suffixed with a double asterisk

are required of implementations.

+---------------------------+--------------------------------+

Baseline Fields Values

+---------------------------+--------------------------------+

BitsPerSample 1**

+---------------------------+--------------------------------+

Compression 9**: JBIG coding

+---------------------------+--------------------------------+

DateTime* {ASCII}: date/time in 24-hour

format "YYYY:MM:DD HH:MM:SS"

+---------------------------+--------------------------------+

FillOrder** 1: most significant bit first

2: least significant bit first

+---------------------------+--------------------------------+

ImageDescription* {ASCII}: A string describing

the contents of the image.

+---------------------------+--------------------------------+

ImageWidth 1728**, 2048, 2432, 2592,

3072, 3456, 3648, 4096, 4864

+---------------------------+--------------------------------+

ImageLength** n: total number of scanlines

in image

+---------------------------+--------------------------------+

NewSubFileType** 2: Bit 1 identifies single

page of a multi-page document

+---------------------------+--------------------------------+

Orientation 1**-8, Default 1

+------------------------------------------------------------+

+---------------------------+--------------------------------+

PhotometricInterpretation 0: pixel value 1 means black

** 1: pixel value 1 means white

+---------------------------+--------------------------------+

ResolutionUnit** 2: inch

3: centimeter

+---------------------------+--------------------------------+

RowsPerStrip** n: number of scanlines per

TIFF strip

+---------------------------+--------------------------------+

SamplesPerPixel** 1

+---------------------------+--------------------------------+

Software* {ASCII}: name & release

number of creator software

+---------------------------+--------------------------------+

StripByteCounts** <n>: number of bytes in TIFF

strip

+---------------------------+--------------------------------+

StripOffsets** <n>: offset from beginning of

file to each TIFF strip

+---------------------------+--------------------------------+

XResolution 200, 204**, 300, 400, 408

(written in pixels/inch)

+---------------------------+--------------------------------+

YResolution 98**, 196**, 100,

200, 300, 391, 400

(written in pixels/inch)

+---------------------------+--------------------------------+

Extension Fields

+---------------------------+--------------------------------+

DocumentName* {ASCII}: name of document

scanned

+---------------------------+--------------------------------+

PageNumber** n,m: page number followed by

total page count

+---------------------------+--------------------------------+

New Fields

+---------------------------+--------------------------------+

GlobalParametersIFD* IFD: global parameters IFD

+---------------------------+--------------------------------+

ProfileType* n: type of data stored in file

+---------------------------+--------------------------------+

FaxProfile* n: ITU-compatible fax mode

+---------------------------+--------------------------------+

CodingMethods* n: compression algorithms used

in file

+---------------------------+--------------------------------+

6. Base Color Fax Mode

6.1. Overview

This section defines the lossy color mode or Profile C of TIFF for

facsimile. Implementations of this profile are required to also

implement Profile S.

This is the base mode for color and grayscale facsimile, which means

that all applications that support color fax must support this mode.

The basic approach is the lossy JPEG compression [T.4, Annex E; T.81]

of L*a*b* color data [T.42]. Grayscale applications use the L*

lightness component; color applications use the L*, a* and b*

components.

This mode uses a new PhotometricInterpretation field value to

describe the L*a*b* encoding specified in [T.42]. This encoding

differs in two ways from the other L*a*b* encodings used in TIFF

[TIFF, TTN1]: it specifies a different default range for the a* and

b* components, based on a comprehensive evaluation of existing

hardcopy output, and it optionally allows selectable range for the

L*, a* and b* components.

6.2. Required TIFF Fields

This section lists the required fields, in addition to those given in

Section 2.2.1, and the values they must support to be compatible with

ITU-T Rec. T.42 and Annex E in ITU-T Rec. T.4.

6.2.1. Baseline Fields

ImageWidth(256). SHORT or LONG

This mode supports the following fixed page widths: 864, 1024, 1216,

1728, 2048, 2432, 2592, 3072, 3456, 3648, 4096, 4864.

NewSubFileType(254) = (Bit 1=1). LONG

RequiredByTIFFforFAX

Bit 1 is 1 if the image is a single page of a multi-page document.

Default = 0 (no subfile bits on, so may not be omitted for fax)

BitsPerSample(258) = 8, 12. SHORT

Count = SamplesPerPixel

The base color fax mode requires 8 bits per sample, with 12 as an

option. 12 bits per sample is not baseline TIFF.

Compression(259) = 7. SHORT

Base color fax mode uses Baseline JPEG compression. Value 7

represents JPEG compression as specified in [TTN2].

FillOrder(266) = 1 , 2. SHORT

RequiredByTIFFBaseline

Profile C 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

PhotometricInterpretation(262) = 10. SHORT

Base color fax mode requires pixel values to be stored using the CIE

L*a*b* encoding defined in ITU-T Rec. T.42. This encoding is

indicated by the PhotometricInterpretation value 10, referred to as

ITULAB. With this encoding, the minimum sample value is mapped to 0

and the maximum sample value is mapped to (2^n - 1), i.e. the

maximum value, where n is the BitsPerSample value. The conversion

from unsigned ITULAB-encoded samples values to signed CIE L*a*b*

values is determined by the Decode field; see Sec. 6.2.3

NOTE: PhotometricInterpretation values 8 and 9 specify encodings for

use with 8-bit-per-sample CIE L*a*b* [TIFF] and ICC L*a*b* [TTN1]

data, but they are fixed encodings, which use different minimum and

maximum samples than the T.42 default encoding. As currently defined,

they are not able to represent fax-encoded L*a*b* data.

ResolutionUnit(296) = 2, 3. SHORT

The unit of measure for resolution. 2 = inch, 3 = centimeter;

Default = 2 (field may be omitted if this is the value)

SamplesPerPixel(277) = 1, 3. SHORT

1: L* component only, required in base color mode

3: L*, a*, b* components

Encoded according to PhotometricInterpretation field

XResolution(282) = 100, 200, 300, 400. RATIONAL

YResolution(283) = 100, 200, 300, 400. RATIONAL

The resolution of the image is expressed in pixels per resolution

unit. In pixels per inch, allowed XResolution values are: 100, 200,

300, and 400. The base color fax mode requires the pixels to be

square, hence YResolution must equal XResolution. Base resolution is

200 pixels per inch and SHALL be supported by all implementations of

this mode. See Section 2.2.2 for inch-metric equivalency.

NOTE: Not all combinations of XResolution, YResolution and ImageWidth

are legal. The following table gives the legal combinations for inch-

based resolutions and the corresponding paper sizes [T.30].

+--------------------------------+---------------------------+

XResolution x YResolution ImageWidth

+--------------------------------+---------------------------+

100 x 100 864 1024 1216

+--------------------------------+---------------------------+

200 x 200 1728 2048 2432

+--------------------------------+---------------------------+

300 x 300 2592 3072 3648

+--------------------------------+---------------------------+

400 x 400 3456 4096 4864

+--------------------------------+---------------------------+

Letter,A4 B4 A3

Legal

+---------------------------+

Paper Size

+---------------------------+

6.2.2 Extension Fields

The JPEG compression standard allows for the a*b* chroma components of

an image to be subsampled relative to the L* lightness component. The

extension fields ChromaSubSampling and ChromaPositioning define the

subsampling. They are the same as YCbCrSubSampling and YCbCrPositioning

in [TIFF], but have been renamed to reflect their applicability to other

color spaces.

ChromaSubSampling(530). SHORT

Count = 2

Specifies the subsampling factors for the chroma components of a

L*a*b* image. The two subfields of this field, ChromaSubsampleHoriz

and ChromaSubsampleVert, specify the horizontal and vertical

subsampling factors respectively.

SHORT 0: ChromaSubsampleHoriz = 1, 2.

1: equal numbers of lightness and chroma samples horizontally,

2: twice as many lightness samples as chroma samples horizontally,

SHORT 1: ChromaSubsampleVert = 1, 2.

1: equal numbers of lightness and chroma samples vertically,

2: twice as many lightness samples as chroma samples vertically,

The default value for ChromaSubSampling is (2,2), which is the

default for chroma subsampling in color fax [T.4, Annex E]. No

chroma subsampling, i.e. ChromaSubSampling = (1,1), is an option

for color fax

ChromaPositioning(531) = 1. SHORT

Specifies the spatial positioning of chroma components relative to

the lightness component.

1: centered,

A value of 1 means chrominance samples are spatially offset and

centered with respect to luminance samples. See the current TIFF

specification under YcbCr positioning for further information.

Default = 1, which is what ITU-T T.4, Annex E specifies.

6.2.3. New Fields

Decode(433). SRATIONAL

Count = 2 * SamplesPerPixel

Describes how to map image sample values into the range of values

appropriate for the current color space. In general, the values are

taken in pairs and specify the minimum and maximum output value for

each color component. For the base color fax mode, Decode has a

count of 6 values and maps the unsigned ITULAB-encoded sample values

(Lsample, asample, bsample) to signed L*a*b* values, as follows:.

L* = Decode[0] + Lsample x (Decode[1]-Decode[0])/(2^n -1)

a* = Decode[2] + asample x (Decode[3]-Decode[2])/(2^n -1)

b* = Decode[4] + bsample x (Decode[5]-Decode[4])/(2^n -1)

where Decode[0], Decode[2] and Decode[4] are the minimum values for

L*, a* and b*; Decode[1], Decode[3] and Decode[5] are the maximum

values for L*, a* and b*; and n is the BitsPerSample, either 8 or

12. For example, when n=8, L*=Decode[0] when Lsample=0 and

L*=Decode[1] when Lsample=255.

ITU-T Rec. T.42 specifies the ITULAB encoding in terms of a range

and offset for each component, which are related to the minimum and

maximum values as follows:

minimum = - (range x offset) / 2^n - 1

maximum = minimum + range

The Decode field default values depend on the color space. For the

ITULAB color space encoding, the default values correspond to the

base range and offset, as specified in ITU-T Rec. T.42 [T.42]. The

following table gives the base range and offset values for

BitsPerSample=8 and 12, and the corresponding default minimum and

maximum default values for the Decode field, calculated using the

equations above when PhotometricInterpetation=10.

+-----------------------------------------------+

ITU-T Rec. T.42 Decode

+---------+----------- base values default values

BitsPer + Component +------------------+----------------------------+

-Sample Range Offset Min Max

+---------+-----------+--------+---------+--------------+-------------+

8 L* 100 0 0 100

+-----------+--------+---------+--------------+-------------+

a* 170 128 -21760/255 21590/255

+-----------+--------+---------+--------------+-------------+

b* 200 96 -19200/255 31800/255

+---------+-----------+--------+---------+--------------+-------------+

12 L* 100 0 0 100

+-----------+--------+---------+--------------+-------------+

a* 170 2048 -348160/4095 347990/4095

+-----------+--------+---------+--------------+-------------+

b* 200 1536 -307200/4095 511800/4095

+---------+-----------+--------+---------+--------------+-------------+

For example, when PhotometricInterpretation=10 and BitsPerSample=8,

the default value for Decode is (0, 100, -21760/255, 21590/255,

-19200/255, 31800/255).

6.3. Recommended TIFF Fields

See Sections 2.2.3. and 2.2.4.

6.4 Base Color Fax Mode Summary

Recommended fields are shown with an asterisk *

Required fields or values are shown with a double asterisk **. If the

double asterisk is on the field name, then all the listed values are

required of implementations; if the double asterisks are in the

Values column, then only the values suffixed with a double asterisk

are required of implementations.

+---------------------------+--------------------------------+

Baseline Fields Values

+---------------------------+--------------------------------+

BitsPerSample 8**: 8 bits per color sample

12: optional 12 bits/sample

+---------------------------+--------------------------------+

Compression** 7: JPEG

+---------------------------+--------------------------------+

DateTime* {ASCII}: date/time in 24-hour

format "YYYY:MM:DD HH:MM:SS"

+---------------------------+--------------------------------+

+------------------------------------------------------------+

FillOrder** 1: most significant bit first

2: least significant bit first

+---------------------------+--------------------------------+

ImageDescription* {ASCII}: A string describing

the contents of the image.

+---------------------------+--------------------------------+

ImageWidth 864, 1024, 1216, 1728**, 2048

2432, 2592, 3072, 3456, 3648

4096, 4864

+---------------------------+--------------------------------+

ImageLength** n: total number of scanlines

in image

+---------------------------+--------------------------------+

NewSubFileType** 2: Bit 1 identifies single page

of a multi-page document

+---------------------------+--------------------------------+

Orientation 1**-8, Default 1

+---------------------------+--------------------------------+

PhotometricInterpretation 10**: ITULAB

+---------------------------+--------------------------------+

ResolutionUnit** 2: inch

3: centimeter

+---------------------------+--------------------------------+

RowsPerStrip** n: number of scanlines per

TIFF strip

+---------------------------+--------------------------------+

SamplesPerPixel 1**: L* (lightness)

3: LAB

+---------------------------+--------------------------------+

Software* {ASCII}: name & release number

of creator software

+---------------------------+--------------------------------+

StripByteCounts** <n>: number or bytes in

TIFF strip

+---------------------------+--------------------------------+

StripOffsets** <n>: offset from beginning

of file to each TIFF strip

+---------------------------+--------------------------------+

XResolution 100, 200**, 300, 400 (written

in pixels/inch)

+---------------------------+--------------------------------+

YResolution 100, 200**, 300, 400

(must equal XResolution)

+---------------------------+--------------------------------+

+---------------------------+--------------------------------+

Extension Fields

+---------------------------+--------------------------------+

DocumentName* {ASCII}: name of scanned

document

+---------------------------+--------------------------------+

PageNumber** n,m: page number followed by

total page count

+---------------------------+--------------------------------+

ChromaSubSampling (1,1), (2, 2)**

(1, 1): equal numbers of

lightness and chroma samples

horizontally and vertically

(2, 2): twice as many lightness

samples as chroma samples

horizontally and vertically

+---------------------------+--------------------------------+

ChromaPositioning 1**: centered

+---------------------------+--------------------------------+

New Fields

+---------------------------+--------------------------------+

Decode** minL, maxL, mina, maxa, minb,

maxb: minimum and maximum

values for L*a*b*

+---------------------------+--------------------------------+

GlobalParametersIFD* IFD: IFD containing

global parameters

+---------------------------+--------------------------------+

ProfileType* n: type of data stored in

TIFF file

+---------------------------+--------------------------------+

FaxProfile* n: ITU-compatible fax mode

+---------------------------+--------------------------------+

CodingMethods* n: compression algorithms

used in file

+---------------------------+--------------------------------+

VersionYear* byte sequence: year of ITU std

+---------------------------+--------------------------------+

7. Lossless Color Mode

This section defines the lossless color mode or Profile L of TIFF for

facsimile. Implementations of this profile are required to also

implement Profiles S and C.

7.1. Overview

This mode, defined in [T.43], uses JBIG to losslessly code three

types of color and grayscale images: one bit per color CMY, CMYK and

RGB images; a palettized (i.e. mapped) color image; and continuous

tone color and grayscale images. The last two are multi-level and use

the L*a*b* encoding specified in [T.42].

7.1.1. Color Encoding

While under development, this mode was called T.Palette, as one of

its major additions was palette or mapped color images. Baseline TIFF

only allows RGB color maps, but ITU-T Rec. T.43 requires L*a*b* color

maps, using the encoding specified in ITU-T Rec. T.42. Palette color

images are expressed with indices (bits per sample) of 12 bits or

less, or optionally 13 to 16 bits, per [T.43].

Enabling T.43 color maps in TIFF requires the extension field

Indexed, defined in [TTN1], and the PhotometricInterpretation field

value 10, defined in Section 6.2.1. The following table shows the

corresponding PhotometricInterpretation, SamplesPerPixel,

BitsPerSample and Indexed field values for the different T.43 image

types.

+----------------------------------------------------------+

Image Type PhotometricIn Samples Bits Per Indexed

-terpretation PerPixel Sample

------------+-------------+----------+----------+---------

RGB 2=RGB 3 1 0

+----------------------------------------------------------+

CMY 5=CMYK 3 1 0

+------------+-------------+----------+----------+---------+

CMYK 5=CMYK 4 1 0

+------------+-------------+----------+----------+---------+

Palette 10=ITULAB 1 n 1

+------------+-------------+----------+----------+---------+

Grayscale 10=ITULAB 1 8, 12 0

+------------+-------------+----------+----------+---------+

Color 10=ITULAB 3 8, 12 0

+------------+-------------+----------+----------+---------+

7.1.2. JBIG Encoding

T.43 uses the single-progression sequential mode of JBIG, defined in

ITU-T Rec. T.82. To code multi-level images using JBIG, which is a

bi-level compression method, an image is resolved into a set of bit-

planes, and each bit-plane is then JBIG compressed. For continuous

tone color and grayscale images, Gray code conversion is used. The

Gray code conversion is part of the data stream encoding, and is

therefore invisible to TIFF.

7.2. Required TIFF Fields

This section lists the required fields, in addition to those in

Section 2.2.1, and the values they must have to be compatible with

ITU-T Rec. T.43.

7.2.1. Baseline Fields

ImageWidth(256). SHORT or LONG

Same page widths as the base color mode; see Section 6.2.1.

NewSubFileType(254) = (Bit 1=1). LONG

RequiredByTIFFforFAX

Bit 1 is 1 if the image is a single page of a multi-page document.

Default = 0 (no subfile bits on, so may not be omitted for fax)

BitsPerSample(258) = 1, 2-8, 9-16. SHORT

Count = SamplesPerPixel

RGB, CMY, CMYK: 1 bit per sample

Continuous tone (L*a*b*): 2-8 bits per sample, 9-12 bits optional

Palette color: 12 or fewer bits per sample, 13-16 bits optional

Note: More than 8 bits per sample is not baseline TIFF.

ColorMap(320). SHORT

Count = 3 * number of sample values

Lossless color fax mode supports palette-color (indexed) images

where the single component value is used as an index into a full

color lookup table stored in the ColorMap field. The sample value is

encoded using the number of bits given by the BitsPerSample field

value. However, per [T.43],the number of sample values may be less

than 2**BitsPerSample. The color lookup table is only required to

have as many entries as there are number of sample values. For

palette-color images in lossless color fax mode, the ITULAB encoding

with 8 or optionally 12 bits per color map value is supported. To

utilize a color map, the TIFF Indexed field must be present. TIFF

orders the color map values so that all the L* values come first,

followed by all the a* values and then all the b* values. Because

ITU-T Rec. T.43 specifies a "chunky" ordering with the L*a*b*

components of the first value, followed by those of the second

value, and so on, reproducing color map values from a fax data

stream in a TIFF file requires reordering values.

Compression(259) = 10. SHORT

10: ITU-T Rec. T.43 representation, using ITU-T Rec. T.82 (JBIG)

coding

FillOrder(266) = 1 , 2. SHORT

RequiredByTIFFBaseline

Profile 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

PhotometricInterpretation(262) = 2, 5, 10. SHORT

2: RGB

5: CMYK, including CMY

10: ITULAB

Image data may also be stored as palette color images, where pixel

values are represented by a single component that is an index into a

color map using the ITULAB encoding. This color map is specified by

the ColorMap field. To use palette color images, set the

PhotometricInterpretation to 10,SamplesPerPixel to 1, and Indexed to

1. The color map is stored in the ColorMap field. See Section 7.1.1

for further discussion on the color encoding.

ResolutionUnit(296) = 2, 3. SHORT

The unit of measure for resolution. 2 = inch, 3 = centimeter;

Default = 2 (field may be omitted if this is the value)

SamplesPerPixel(277) = 1, 3, 4. SHORT

1: Palette color image, or L*-only if Indexed = 0 and

PhotometricInterpretation is 10 (ITULAB).

3: RGB, or L*a*b*, or CMY if PhotometricInterpretation is 5 (CMYK).

4: CMYK.

XResolution(282) = 100, 200, 300, 400. RATIONAL

YResolution(283) = 100, 200, 300, 400. RATIONAL

The resolution of the image is expressed in pixels per resolution

unit. In pixels per inch, allowed XResolution values are: 100, 200,

300, and 400. The lossless color fax mode requires the pixels to be

square, hence YResolution must equal XResolution. Base resolution is

200 pixels per inch. See Section 2.2.2 for inch-metric equivalency.

7.2.2. Extension Fields

Indexed(364) = 0, 1. SHORT

0: not a palette-color image

1: palette-color image

This field is used to indicate that each sample value is an index

into an array of color values specified in the ColorMap field.

Lossless color fax mode supports palette-color images with the

ITULAB encoding. The SamplesPerPixel value must be 1.

7.2.3. New Fields

Decode(433) SRATIONAL

Decode is used in connection with the ITULAB encoding of image data

and color map values; see Section 6.2.3.

7.3. Recommended TIFF Fields

See Sections 2.2.3. and 2.2.4.

7.4. Lossless Color Fax Mode Summary

Recommended fields are shown with an asterisk *.

+--------------------+--------------------------------------+

Baseline Fields Values

+--------------------+--------------------------------------+

BitsPerSample 1: Binary RGB, CMY(K)

8: 8 bits per color sample

9-16: optional

+--------------------+--------------------------------------+

ColorMap n: LAB color map

+--------------------+--------------------------------------+

Compression 10: JBIG, per T.43

+--------------------+--------------------------------------+

DateTime* {ASCII}: date/time in the 24-hour

format "YYYY:MM:DD HH:MM:SS"

+--------------------+--------------------------------------+

FillOrder** 1: Most significant bit first

2: Least significant bit first

+--------------------+--------------------------------------+

ImageDescription* {ASCII}: A string describing the

contents of the image.

+--------------------+--------------------------------------+

ImageWidth 864, 1024, 1216, 1728**, 2048, 2432,

2592, 3072, 3456, 3648, 4096, 4864

+--------------------+--------------------------------------+

ImageLength** n: total number of scanlines in image

+--------------------+--------------------------------------+

NewSubFileType 2: Bit 1 identifies single page of a

multi-page document

+--------------------+--------------------------------------+

Orientation 1**-8, Default 1

+--------------------+--------------------------------------+

PhotometricInter- 2: RGB

pretation 5: CMYK

10: ITULAB

+--------------------+--------------------------------------+

+--------------------+--------------------------------------+

ResolutionUnit 2: inch

3: centimeter

+--------------------+--------------------------------------+

RowsPerStrip n: number of scanlines per TIFF strip

+--------------------+--------------------------------------+

SamplesPerPixel 1: L* (lightness)

3: LAB, RGB, CMY

4: CMYK

+--------------------+--------------------------------------+

Software* {ASCII}: name & release number of

creator software

+--------------------+--------------------------------------+

StripByteCounts <n>: number or bytes in TIFF strip

+--------------------+--------------------------------------+

StripOffsets <n>: offset from beginning of file to

each TIFF strip

+--------------------+--------------------------------------+

XResolution 100, 200, 300, 400 (written in

pixels/inch)

+--------------------+--------------------------------------+

YResolution equal to XResolution (pixels must be

square)

+--------------------+--------------------------------------+

Extension Fields

+--------------------+--------------------------------------+

DocumentName* {ASCII}: name of scanned document

+--------------------+--------------------------------------+

PageNumber n,m: page number followed by total

page count

+--------------------+--------------------------------------+

Indexed 0: not a palette-color image

1: palette-color image

+--------------------+--------------------------------------+

New Fields

+--------------------+--------------------------------------

Decode minL, maxL, mina, maxa, minb, maxb:

minimum and maximum values for L*a*b*

+--------------------+--------------------------------------+

GlobalParameters IFD: global parameters IFD

IFD*

+-----------------------------------------------------------+

+--------------------+--------------------------------------+

ProfileType* n: type of data stored in TIFF file

+--------------------+--------------------------------------+

FaxProfile* n: ITU-compatible fax mode

+--------------------+--------------------------------------+

CodingMethods* n:compression algorithms used in

file

+--------------------+--------------------------------------+

VersionYear* byte sequence: year of ITU fax std

+--------------------+--------------------------------------+

8. Mixed Raster Content Mode

This section defines the Mixed Raster Content mode or Profile M of

TIFF for facsimile. Implementations of this profile are required to

implement Profiles S and C, and may optionally implement Profiles F,

J and L.

8.1. Overview

Unlike previous fax modes, which use a single coding method and

spatial resolution for an entire fax page, the Mixed Raster Content

mode [T.44] enables different coding methods and resolutions within a

single page. For example, consider a page that contains black-and-

white text, which is best coded with MMR or JBIG, a color bar chart,

best coded with JBIG, and a scanned color image, best coded with

JPEG. Similarly, while spatial resolution of 400 pixels per inch may

be best for the black-and- white text, 200 pixel per inch is usually

sufficient for a color image.

Rather than applying one coding method and resolution to all

elements, MRC allows multiple coders and resolutions within a page.

By itself, MRC does not define any new coding methods or resolutions.

Instead it defines a 3-layer image model for structuring and

combining the scanned image data. The MRC 3-layer model has been

applied here using the TIFF format to yield a data structure which

differs from [T.44] though it applies the same coding methods, uses

the same compressed image data stream and is consistent with the TIFF

principle of a single IFD per image.

8.1.1. MRC 3-layer model

The 3 layers of the MRC model are Foreground and Background, which

are both multi-level, and Mask, which is bi-level. Each layer may

appear only once on a page and is coded independently of the other

two. In our earlier example, the black-and-white text could be in the

Mask layer, the color chart in the Foreground layer, and the color

image in the Background layer.

Each layer is an image and, when present, is represented by at least

one IFD in a TIFF file. This is consistent with TIFF, which provides

fields to define the attributes, such as resolution, image size, bits

per sample, etc., of a single image or layer. The distribution of

content among layers is determined by the writer, as is the choice of

coding method, color encoding and spatial resolution for a layer.

The final image is obtained by using the Mask layer to select pixels

from the other two layers. When the Mask layer pixel value is 1, the

corresponding pixel from the Foreground layer is selected; when it is

0, the corresponding pixel from the Background layer is selected.

Details are given in the Introduction of [T.44].

Not all pages, and not all parts of a page, require 3 layers. If

there is only one layer present, then that layer is the primary image

or IFD. If there is more than one layer, then the Mask must be one of

the layers, in which case it is the primary image and it must be page

size.

MRC allows a page to be split into strips, with a variable number of

scanlines in a strip. A strip can have 1, 2 or 3 layers. A single,

stripped layer may be stored as a single, stripped image in an IFD,

e.g., all strips associated with the Background layer may be treated

as a single image. Alternatively, each strip associated with a layer

may be stored as a separate image or IFD, e.g., the Background layer

can be composed of several images that are offset vertically with

respect to the page. In this case, there can be no overlap between

images associated with a single layer. According to [T.4] Annex G,

strips having more than 1 layer SHOULD NOT be more than 256 lines in

length unless the capability to receive longer strips has been

negotiated.

Furthermore, color fax also requires the spatial resolutions of

Background and Foreground images to be legal fax values that are also

integer factors of the Mask image resolution. For example, if the

Mask Layer resolution is 400 pixels per inch, then allowed

resolutions for the Foreground and Background layers are 100, 200 or

400 pixels per inch; if the Mask is at 300 pixels per inch, then

allowed values are 100 and 300. The Foreground and Background layer

resolutions can be independently set.

8.1.2. A TIFF Representation for the MRC 3-layer model

In the TIFF representation of the 3-layer MRC model, each page is

represented by a single IFD, called the Primary IFD, that represents

the Mask layer (unless the Foreground or Background is the single

layer present), and a set of child IFDs that are referenced through

the SubIFDs extension field [TTN1]. To distinguish MRC-specific

SubIFDs from other SubIFDs, the NewSubFileType field MUST have Bit 4

ON, indicating an MRC-related IFD. A new ImageLayer field is also

introduced that consists of two values that identify the layer

(Foreground, Background, or Mask) and the order within the layer

(first, second, ... image of the layer); see Section 8.2.3.

Because MRC allows strips with variable numbers of scanlines, a

reader MUST support StripRowCounts field because a writer may use it

in place of the RowsPerStrip field in this mode. The StripRowCounts

field allows each layer, with a variable number of scanlines in each

strip, to be represented by a single IFD, when the coding parameters

are the same for all strips in the layer. The MRC standard [T.44]

allows the Foreground and Background layers to have strips with

different coding parameters. In this case, a separate IFD is required

to represent the strips which use different coding parameters; see

text in next paragraph. In all cases, the Mask layer is required to

be represented by a single IFD and a single set of coding parameters.

The use of SubIFDs to store child IFDs is described in [TTN1]. An

example is shown graphically below. The Primary IFD associated with

page 1 (PrimaryIFD 0) points to page 2 (PrimaryIFD 1) with the

nextIFD offset. The Primary IFD, corresponding to the Mask layer

(ImageLayer=[2,1]), contains a SubIFDs field that points to a list of

child IFDs. The first child IFD represents one image of the

Background layer, i.e., ImageLayer=[1,1]. This child IFD points to

the second child IFD via the nextIFD offset. This child represents

the second Background layer image, ImageLayer=[1,2]. Finally, the

second child points to the third child, which corresponds to the

single Foreground layer image, ImageLayer=[3,1]. The next IFD offset

associated with this Foreground image is 0, indicating no more child

IFDs exist. Each primary IFD has the NewSubFileType set to 18,

indicating the IFD is MRC-specific (bit 4) and that it is a single

page of a multi-page document (bit 1). Each child IFD has the

NewSubFileType set to 16, indicating the IFD is MRC-specific. The 'V'

character should be read as a down-pointing arrow.

(nextIFD)

PRIMARY IFD 0 ------------> PRIMARY IFD 1--> ...

ImageLayer = [2,1]

NewSubFileType = 18

SubIFDs

V

Child IFD

ImageLayer = [1,1]

NewSubFileType = 16

(nextIFD)

V

Child IFD

ImageLayer = [1,2]

NewSubFileType = 16

(nextIFD)

V

Child IFD

ImageLayer = [3,1]

NewSubFileType = 16

(nextIFD)

V

0

In the example above, the SubIFDs field of the Primary IFD points to

the first IFD in a list of child IFDs. TIFF allows the SubIFDs field

to point to an array of IFDs, each of which can be the first of a

list of IFDs. An MRC-enabled TIFF reader must scan all available

child IFDs to locate and identify IFDs associated with MRC layers.

In the case where the Background or Foreground layers are described

with multiple IFDs, the XPosition and YPosition TIFF fields specify

the offset to the upper-left corner of the IFD with respect to the

Mask layer; see Section 8.2.2. When there is only a single layer

(Mask, Foreground, or Background), it is stored as the Primary IFD.

8.2. Required TIFF Fields

This section describes the TIFF fields required, in addition to those

in Section 2.2.1, to represent MRC mode fax images. Since MRC mode

stores fax data as a collection of images corresponding to layers or

parts of layers, the coding methods, color encodings and spatial

resolutions used by previous modes apply to MRC. Therefore, the

descriptions here will typically reference the appropriate earlier

section. Fields and values specific to MRC mode are pointed out.

8.2.1. Baseline Fields

ImageWidth(256). SHORT or LONG

Same page widths as the base color mode; see Section 6.2.1.

In the MRC mode, the width of a Foreground or Background image in

the coded data stream may be less than the page width. In this case,

the image width in the coded data steam is used to interpret the

coded data, and the value of this field is used as the page width.

NewSubFileType(254) = 16, 18. LONG

For MRC fax mode, the NewSubFileType field has two bits that are

required.

Bit 1 indicates a single page of a multi-page document and must be

set for the Primary IFD;

Bit 4 indicates MRC imaging model as described in ITU-T

Recommendation T.44 [T.44], and must be set for Primary IFDs

and all MRC-specific child IFDs.

BitsPerSample(258) = 1, 2-8, 9-16 SHORT

Compression(259) = 3, 4, 7, 9, 10. SHORT

SamplesPerPixel(277) = 1, 3, 4. SHORT

FillOrder(266) = 1 , 2. SHORT

RequiredByTIFFBaseline

Profile 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

ResolutionUnit(296) = 2, 3. SHORT

PhotometricInterpretation(262) = 0, 1, 2, 5, 10. SHORT

For Mask layer, see Sections 4.2.1 and 5.2.1.

For Foreground and Background layers, see Sections 6.2.1 and 7.2.1.

ColorMap(320). SHORT

Count = 3 * (2**BitsPerSample)

Used when Foreground or Background layer is a palette-color image;

see Section 7.2.1.

XResolution(282) = 100, 200, 300, 400. RATIONAL

YResolution(283) = 100, 200, 300, 400. RATIONAL

The resolution of the image is expressed in pixels per resolution

unit. In pixels per inch, allowed XResolution values for all layers

are: 100, 200, 300, and 400. MRC color fax mode requires the pixels

to be square, hence YResolution must equal XResolution for all

layers. The resolution of Background and Foreground layers must each

be an integer factor of the Primary image, which is the Mask layer,

when it is present; see Section 8.4.

See Section 2.2.2 for inch-metric equivalency.

8.2.2. Extension Fields

ChromaSubSampling(530). SHORT

ChromaPositioning(531). SHORT

For Foreground and Background layers, see Section 6.2.2.

Indexed(346) = 0, 1. SHORT

For Foreground and Background layers: 1 indicates a palette-color

image, see Section 7.2.2.

T4Options(292) = 0, 1, 4, 5. SHORT

T6Options(293) = 0. SHORT

For Mask layer, see Section 4.2.2.

SubIFDs(330). IFD

Count = number of child IFDs

Each value is an offset from the beginning of the TIFF file to a

child IFD [TTN1].

XPosition(286). RATIONAL

YPosition(287). RATIONAL

Specifies the horizontal and vertical offsets of the top-left of the

IFD from the top-left of the Primary IFD in page resolution units.

For example, if the Primary IFD is at 400 pixels per inch, and a

foreground layer IFD is at 200 pixels per inch and located at pixel

coordinate (345, 678) with respect to the Primary IFD, the XPosition

value is 345/400 and the YPosition value is 678/400.

Color fax does not currently allow overlap of any component images

within a single layer.

Default values for XPosition and YPosition are 0.

8.2.3. New Fields

Decode(433). SRATIONAL

For Foreground and Background layers, see Section 6.2.3.

DefaultImageColor(434). SHORT

Count = SamplesPerPixel

In areas where no image data is available, a default color is needed

to specify the color value. If the StripByteCounts value for a strip

is 0, then the color for that strip must be defined by a default

image color.

The DefaultImageColor field uses the same encoding as the image

data, and its value is therefore interpreted using the

PhotometricInterpretation, SamplesPerPixel, BitsPerSample, and

Indexed fields. If the fax data stream requires a different

encoding, then transferring the default color value between a TIFF

file and fax data stream requires a color conversion.

For the Foreground layer image, the default value for the

DefaultImageColor field is black. For other cases, including the

Background layer image, the default value is white.

StripRowCounts(559). LONG

Count = number of strips

The number of scanlines stored in a strip. MRC allows each fax strip

to store a different number of scanlines. For strips with more than

one layer there is a maximum strip size of 256 scanlines or full

page size. The 256 maximum SHOULD be used unless the capability to

receive longer strips has been negotiated. This field replaces

RowsPerStrip for IFDs with variable-sized strips. Only one of the

two fields, StripRowCounts and RowsPerStrip, may be used in an IFD.

ImageLayer (34732). SHORT or LONG.

Count = 2

Image layers are defined such that layer 1 is the Background layer,

layer 3 is the Foreground layer, and layer 2 is the Mask layer,

which selects pixels from the Background and Foreground layers. The

ImageLayer tag contains two values, describing the layer to which

the image belongs and the order in which it is imaged.

ImageLayer[0] = 1, 2, 3.

1: Image is a Background image, i.e., the image that will appear

whenever the Mask contains a value of 0. Background images

typically contain low-resolution, continuous-tone imagery.

2: Image is the Mask layer. In MRC, if the Mask layer is present, it

must be the Primary IFD and be full page in extent (no gaps.)

3: Image is a Foreground image, i.e., the image that will appear

whenever the Mask contains a value of 1. The Foreground image

generally defines the color of text or lines, but may also

contain high-resolution imagery.

ImageLayer[1]:

1: first image to be imaged in this layer,

2: second image to be imaged in this layer,

3: ...

Value describing the image order. In MRC, this may be considered

the strip number. Since MRC mode currently does not allow overlap

between images within a layer, the order value does not have any

visual effect.

In MRC fax mode, it is possible that only a single layer is

transmitted. For example, if a page contains only a single

continuous-tone photograph, then only the Background layer may be

transmitted. In this case, the Background layer will be stored as the

Primary IFD. ImageLayer[0] will be 1 indicating Background;

ImageLayer[1] will be 1 since there can be no other IFDs associated

with that layer. No Mask layer will exist.

8.3. Recommended TIFF Fields

See Sections 2.2.3. and 2.2.4.

8.4. Rules and Requirements for Images

The MRC mode defines a fundamental set of rules for images in the 3-

layer representation.

1. If more than one layer exists, then the binary Mask layer SHALL be

present and be the primary image. The Mask layer SHALL support the

encoding defined in Section 3 and MAY support the encodings

defined in Sections 4 and 5. If only one layer exists, then the

image corresponding to that layer is the primary image.

2. When the binary Mask layer is the Primary IFD, the Primary IFD

defines and extends to the entire page boundary; all attached

model images cannot extend beyond the Primary image. Resolution

differences may cause some pixels to "hang over" the page

boundary, but no new pixels should exist completely beyond the

page extent. When the Foreground or Background layer is the

Primary IFD, the Primary IFD may not be page width.

3. The Background and Foreground images SHALL support the color

encoding defined in Section 6 and MAY support the color encoding

defined in Section 7. These images MAY optionally cover only a

portion of the strip or page.

4. Each Primary IFD and each MRC-specific SubIFD must have an

ImageLayer field to specify which layer the IFD belongs to, and

the imaging order of that IFD within the layer.

5. Each Primary IFD must have a NewSubFileType field value set to 18,

indicating a single page of a multi-page document (bit 1) and MRC

mode (bit 4).

6. Each MRC-specific child IFD must have a NewSubFileType field value

set to 16, indicating MRC mode (bit 4).

7. In MRC mode, each layer is transmitted as a sequence of strips. It

is possible that each strip of each layer can be stored as a

separate IFD. In this case, the SubIFDs structure pointed to by

the Primary IFD will contain several IFDs that have an ImageLayer

field with the layer identified as either Background (layer 1) or

Foreground (layer 3). There may be no overlap in the vertical

direction between IFDs associated with a single layer, although

there may be a gap from one of these images to the next. The TIFF

XPosition and YPosition fields are used to indicate the placement

of these images with respect to the primary image.

8. When the Mask image is present, the resolution of Background and

Foreground images must each be an integer factor of the Mask

image. For example, if the Mask image is 400 pixels/inch, then the

Background or Foreground image may be at 400 pixels/inch (400/1),

200 pixels/inch (400/2) or 100 pixels/inch (400/4).

8.5. MRC Fax Mode Summary

Recommended fields are shown with an asterisk *

+------------------+-----------------------------------------+

Baseline Fields Values

-----------------------------------------------------------

BitsPerSample 1: binary mask

8: 8 bits per color sample

9-16: optional 12 bits/sample

+------------------+-----------------------------------------+

ColorMap n: LAB color map

+------------------+-----------------------------------------+

Compression 3: Modified Huffman and Modified Read

4: Modified Modified Read

7: JPEG

9: JBIG, per T.85

10: JBIG, per T.43

+------------------+-----------------------------------------+

DateTime* {ASCII): date/time in the 24-hour format

"YYYY:MM:DD HH:MM:SS"

+------------------+-----------------------------------------

FillOrder** 1: Most significant bit first

2: Least significant bit first

+------------------+-----------------------------------------

ImageDescription* {ASCII}: A string describing the

contents of the image.

+------------------+-----------------------------------------+

ImageWidth 864, 1024, 1216, 1728**, 2048, 2432,

2592, 3072, 3456, 3648, 4096, 4864

+------------------+-----------------------------------------+

ImageLength** n: total number of scanlines in image

+------------------+-----------------------------------------+

NewSubFileType 16, 18:

Bit 1 indicates single page of a multi-

page document on Primary IFD

Bit 4 indicates MRC model

+------------------+-----------------------------------------+

+------------------+-----------------------------------------+

Orientation 1**-8, Default 1

+------------------+-----------------------------------------+

PhotometricInter 0: WhiteIsZero

pretation 1: BlackIsZero

2: RGB

5: CMYK

10: ITULAB

+------------------+-----------------------------------------+

ResolutionUnit 2: inch

3: centimeter

+------------------+-----------------------------------------+

RowsPerStrip n: number or scanlines per strip

+------------------+-----------------------------------------+

SamplesPerPixel 1: L* (lightness)

3: RGB, LAB, CMY

4: CMYK

+------------------+-----------------------------------------+

Software* {ASCII}: name & release number of

creator software

+------------------+-----------------------------------------+

StripByteCounts <n>: number or bytes in each strip

+------------------+-----------------------------------------+

StripOffsets <n>: offset from beginning of file to

each TIFF strip

+------------------+-----------------------------------------

XResolution 100, 200, 300, 400 (written in

pixels/inch)

+------------------+-----------------------------------------

YResolution equal to XResolution (pixels must be

square)

+------------------+-----------------------------------------+

Extension Fields

+------------------+-----------------------------------------+

T4Options 0: required if Compression is Modified

Huffman, EOLs not byte aligned

1: required if Compression 2D Modified

Read, EOLs are not byte aligned

4: required if Compression Modified

Huffman, EOLs byte aligned

5: required if Compression 2D Modified

Read, EOLs are byte aligned

+------------------+-----------------------------------------+

T6Options 0: required if Compression is 2D

Modified Modified Read

+------------------+-----------------------------------------+

+------------------+-----------------------------------------+

DocumentName* {ASCII}: name of scanned document

+------------------+-----------------------------------------+

PageNumber n,m: page number followed by total page

count

+------------------+-----------------------------------------+

ChromaSubSampling (1,1), (2, 2)**

(1, 1): equal numbers of lightness and

chroma samples horizontally & vertically

(2, 2): twice as many lightness samples

as chroma horizontally and vertically

+------------------+-----------------------------------------+

ChromaPositioning 1: centered

+------------------+-----------------------------------------+

Indexed 0: not a palette-color image

1: palette-color image

+------------------+-----------------------------------------+

SubIFDs <IFD>: byte offset to fg/bg IFDs

+------------------+-----------------------------------------+

XPosition horizontal offset in primary IFD

resolution units

+------------------+-----------------------------------------+

YPosition vertical offset in primary IFD

resolution units

+------------------+-----------------------------------------+

New Fields

+------------------+-----------------------------------------+

Decode minL, maxL, mina, maxa, minb, maxb:

minimum and maximum values for L*a*b*

+------------------+-----------------------------------------+

DefaultImageColor <n>: background color

+------------------+-----------------------------------------+

StripRowCounts <n>: number of scanlines in each strip

+------------------+-----------------------------------------+

ImageLayer n, m: layer number, imaging sequence

(e.g., strip number)

+------------------+-----------------------------------------+

GlobalParameters IFD: global parameters IFD

IFD*

+------------------+-----------------------------------------+

ProfileType* n: type of data stored in TIFF file

+------------------+-----------------------------------------+

FaxProfile* n: ITU-compatible fax mode

+------------------+-----------------------------------------+

CodingMethods* n: compression algorithms used in file

+------------------+-----------------------------------------+

ModeNumber* n: version of ITU fax standard

+------------------+-----------------------------------------+

+------------------------------------------------------------+

VersionYear* byte sequence: year of ITU fax standard

+------------------+-----------------------------------------+

9. MIME content-type image/tiff

[TIFF-REG] describes the registration of the MIME content-type

image/tiff to refer to TIFF 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

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.

9.1 Refinement of MIME content-type image/tiff for Facsimile

Applications

Since this document defines facsimile specific profiles of TIFF, it

is useful to note an appropriate application parameter for the

image/tiff MIME content-type.

The two values of the image/tiff application parameter as defined for

facsimile are shown below, separated by a comma:

faxbw, faxcolor

The "faxbw" application parameter 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.

The "faxcolor" application parameter is suitable for use by

applications that can process one or more TIFF for facsimile profiles

or subsets that can be used for the encoding of black and white, AND

color facsimile data.

Since this document defines several profiles of TIFF for facsimile,

the following rules should be followed when setting the application

parameter value. For TIFF image data which is encoded for the

profiles of TIFF for Facsimile that support black-and-white image

data (Profiles S, F or J), applications which use one of these

profiles or a subset should set the value of the application

parameter to "faxbw". For TIFF image data which is encoded for the

defined profiles of TIFF for Facsimile that support color image data

(Profiles C, L or M), as well as black-and-white image data,

applications which use one of these profiles or a subset should set

the value of the application parameter to "faxcolor".

An example of the use of the image/tiff MIME Content-type with the

application parameter set with the value 'faxbw' follows:

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.

In a similar respect, an example of the image/tiff MIME Content-type

with the application parameter setting suitable for handling a color

subset or profile of TIFF for facsimile is shown below:

Content-type: image/tiff; application=faxcolor

10. Security Considerations

This document describes a file format for Internet fax, which is a

series of profiles of TIFF for facsimile. As such, it does not create

any security issues not already identified in [TIFF-REG], 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-encoded facsimile messages.

11. References

[REQ] Bradner, S, "Key words for use in RFCs to Indicate Requirement

Levels", RFC2119, March 1997.

[T.4] ITU-T Recommendation T.4, Standardization of group 3 facsimile

apparatus for document transmission, October 1997

[T.6] ITU-T Recommendation T.6, Facsimile coding schemes and coding

control functions for group 4 facsimile apparatus, November 1988

[T.30] ITU-T Recommendation T.30 - Procedures for Document Facsimile

Transmission in the General Switched Telephone Network, June 1996

[T.42] ITU-T Recommendation T.42, Continuous-tone colour

representation method for facsimile, February 1996

[T.43] ITU-T Recommendation T.43, Colour and gray-scale image

representations using lossless coding scheme for facsimile, February

1997

[T.44] ITU-T Recommendation T.44, Mixed Raster Content (MRC), October

1997.

[T.81] ITU-T Recommendation T.81, Information technology - Digital

compression and coding of continuous-tone still images - Requirements

and guidelines, September 1992

[T.82] ITU-T Recommendation T.82, Information technology - Coded

representation of picture and audio information - Progressive bi-

level image compression, March 1995

[T.85] ITU-T Recommendation T.85, Application profile for

Recommendation T.82 - Progressive bi-level image compression (JBIG

coding scheme) for facsimile apparatus, August 1995

[TIFF] Tag Image File Format, Revision 6.0, Adobe Developers

Association, June 3, 1992,

FTP://ftp.adobe.com/pub/adobe/devrelations/

devtechnotes/pdffiles/tiff6.pdf

The TIFF 6.0 specification dated June 3, 1992 specification (c)

1986-1988, 1992 Adobe Systems Incorporated. All Rights Reserved.

[TIFF-FY] Parsons, G. and J. Rafferty, "Tag Image File Format (TIFF)

- F Profile for Facsimile", RFC2306, March 1998.

[TIFF-F0] TIFF Class F specification, Apr 28, 1990,

ftp://ftp.faximum.com/pub/documents/tiff_f.txt

[TIFF-REG] Parsons, G., Rafferty J. and S. Zilles, "Tag Image File

Format (TIFF) - image/tiff MIME Sub-type Registration", RFC2302,

March 1998.

[TTN1] Adobe PageMaker 6.0 TIFF Technical Notes, Sept. 14, 1995,

http://www.adobe.com/supportservice/devrelations/PDFS/TN/TIFFPM6.pdf

[TTN2] Draft TIFF Technical Note 2, Replacement TIFF/JPEG

specification, March 17, 1995,

ftp://ftp.sgi.com/graphics/tiff/TTN2.draft.txt

[VPIM2] Vaudreui,l G. and G. Parsons, "Voice Profile for Internet

Mail - version 2", work in progress, <draft-ema-vpim-06.txt>

The ITU-T Recommendations are available at http://www.itu.ch.

12. Authors' Addresses

Lloyd McIntyre Stephen Zilles

Xerox Corporation Adobe Systems Inc.

Mailstop PAHV-305 Mailstop W14

3400 Hillview Ave. 345 Park Avenue

Palo Alto, CA 94304 USA San Jose, CA 95110-2704, USA

Voice: +1-650-813-6762 Voice: +1-408-536-4766

Fax: +1-650-845-2340 Fax: +1-408-536-4042

Email: lmcintyre@adoc.xerox.com Email: szilles@adobe.com

Robert Buckley Dennis Venable

Xerox Corporation Xerox Corporation

Mailstop 0128-30E Mailstop 0128-27E

800 Phillips Road 800 Phillips Road

Webster, NY 14580, USA Webster, NY 14580, USA

Voice: +1-716-422-1282 Voice: +1-716-422-8009

Fax: +1-716-422-6117 Fax: +1-716-422-6117

Email: Rob_Buckley@wb.xerox.com Email: venable@wrc.xerox.com

Glenn S. Parsons James Rafferty

Northern Telecom Human Communications

P.O. Box 3511, Station C 12 Kevin Drive

Ottawa, ON K1Y 4H7, Canada Danbury, CT 06811-2901, USA

Phone: +1-613-763-7582 Phone: +1-203-746-4367

Fax: +1-613-763-2697 Fax: +1-203-746-4367

Email: Glenn.Parsons@Nortel.ca Email: Jrafferty@worldnet.att.net

Annex A: Summary of TIFF Fields for Internet Fax

This annex includes tables which list by mode the TIFF fields used in

the proposed fax file format. The fields are organized into 3

categories:

1) TIFF Baseline Fields

2) TIFF Extension Fields

3) New Fields.

The tables include the allowed values for each fax mode. Entries

other than explicit numbers are described by:

n - single number

n, m - 2 numbers

a, b, c - 3 numbers

r - rational number

<n> - array of numbers

<b> - byte sequence

{ASCII} - string

IFD - IFD byte offset

<IFD> - array of IFD byte offsets

A blank entry in the table indicates that the field is not used by

that particular fax mode.

Table A.1 TIFF Baseline Fields

+---------------------------------------------------------+

Fax Mode/Profile

+---------------------------------------------------------

Minimal Extended JBIG Lossy Lossless Mixed

+---------- B&W B&W B&W Color Color Raster

TIFF Content

Field S F J C L M

+----------+---------+----------+--------+---------+--------+--------+

BitsPer 1 1 1 8, 12 1, 2-8 1, 2-8

Sample 9-16 9-16

+----------+---------+----------+--------+---------+--------+--------+

ColorMap <n> <n>

+----------+---------+----------+--------+---------+--------+--------+

Compres- 3 3, 4 9 7 10 3, 4, 7

sion 9,10

+----------+---------+----------+--------+---------+--------+--------+

DateTime {ASCII} {ASCII} {ASCII} {ASCII} {ASCII}

+----------+---------+----------+--------+---------+--------+--------+

FillOrder 2 1, 2 1, 2 1, 2 1, 2 1,2

+----------+---------+----------+--------+---------+--------+--------+

+----------+---------+----------+--------+---------+--------+--------+

ImageDes- {ASCII} {ASCII} {ASCII} {ASCII} {ASCII}

cription

+----------+---------+----------+--------+---------+--------+--------+

Image- n n n n n n

Length

+----------+---------+----------+--------+---------+--------+--------+

Image- 1728 1728, 2048, 2432 864, 1024, 1216, 1728,

Width 2592, 3072, 3456 2048, 2432, 2592, 3072,

3648, 4096, 4864 3456, 3648, 4096, 4864

+----------+---------+----------+--------+---------+--------+--------+

NewSub- 2 2 2 2 2 16, 18

FileType

+----------+---------+----------+--------+---------+--------+--------+

Orien- 1 1-8 1-8 1-8 1-8 1-8

tation

+----------+---------+----------+--------+---------+--------+--------+

Photo- 0 0, 1 0, 1 10 2, 5, 0, 1,

metric- 10 2, 5,

Interp- 10

retation

+----------+---------+----------+--------+---------+--------+--------+

Resolu- 2 2, 3 2, 3 2, 3 2, 3 2, 3

tionUnit

+----------+---------+----------+--------+---------+--------+--------+

RowsPer- n n n n n n

Strip

+----------+---------+----------+--------+---------+--------+--------+

Samples- 1 1 1 1, 3 1, 3, 4 1, 3, 4

PerPixel

+----------+---------+----------+--------+---------+--------+--------+

Software {ASCII} {ASCII} {ASCII} {ASCII} {ASCII}

+----------+---------+----------+--------+---------+--------+--------+

Strip- n <n> <n> <n> <n> <n>

Byte-

Counts

+----------+---------+----------+--------+---------+--------+--------+

Strip- n <n> <n> <n> <n> <n>

Offsets

+----------+---------+----------+--------+---------+--------+--------+

XResolu- 204 200, 204, 300 100, 200, 300, 400

tion 200 400, 408

+----------+---------+----------+--------+---------+--------+--------+

YResolu- 98, 196 98, 196, 100, 200 100, 200, 300, 400

tion 100,200 300, 391, 400

+----------+---------+----------+--------+---------+--------+--------+

Table A.2 TIFF Extension Fields

+---------------------------------------------------------+

Fax Mode/Profile

+---------------------------------------------------------

Minimal Extended JBIG Lossy Lossless Mixed

+---------- B&W B&W B&W Color Color Raster

TIFF Content

Field S F J C L M

+----------+---------+----------+--------+---------+--------+--------+

Chroma- 1 1

Position-

ing

+----------+---------+----------+--------+---------+--------+--------+

Chroma- <1, 1> <1, 1>

SubSampl- <2, 2> <2, 2>

ing

+----------+---------+----------+--------+---------+--------+--------+

Document- {ASCII} {ASCII} {ASCII} {ASCII} {ASCII}

Name

+----------+---------+----------+--------+---------+--------+--------+

Indexed 0,1 0,1

+----------+---------+----------+--------+---------+--------+--------+

Page- n, m n, m n, m n, m n, m n, m

Number

+----------+---------+----------+--------+---------+--------+--------+

SubIFDs <IFD>

+----------+---------+----------+--------+---------+--------+--------+

T4Options 0, 4 0, 1, 0, 1,

4, 5 4, 5

+----------+---------+----------+--------+---------+--------+--------+

T6Options 0 0

+----------+---------+----------+--------+---------+--------+--------+

XPosition r

+----------+---------+----------+--------+---------+--------+--------+

YPosition r

+----------+---------+----------+--------+---------+--------+--------+

Table A.3 New Fields

+---------------------------------------------------------+

Fax Mode/Profile

+---------------------------------------------------------

Minimal Extended JBIG Lossy Lossless Mixed

+---------- B&W B&W B&W Color Color Raster

TIFF Content

Field S F J C L M

+----------+---------+----------+--------+---------+--------+--------+

BadFax- n

Lines

+----------+---------+----------+--------+---------+--------+--------+

CleanFax- 0, 1, 2

Data

+----------+---------+----------+--------+---------+--------+--------+

Coding- n n n n

Method

+----------+---------+----------+--------+---------+--------+--------+

Consecu- n

tiveBad-

FaxLines

+----------+---------+----------+--------+---------+--------+--------+

Decode <r> <r> <r>

+----------+---------+----------+--------+---------+--------+--------+

Default- <n>

ImageColor

+----------+---------+----------+--------+---------+--------+--------+

Fax- n n n n

Profile

+----------+---------+----------+--------+---------+--------+--------+

Global- IFD IFD IFD IFD IFD

Parame-

tersIFD

+----------+---------+----------+--------+---------+--------+--------+

Image- n, m

Layer

+----------+---------+----------+--------+---------+--------+--------+

Mode- n

Number

+----------+---------+----------+--------+---------+--------+--------

Profile- n n n n

Type

+--------------------------------------------------------------------+

+----------+---------+----------+--------+---------+--------+--------+

Strip- <n>

RowCounts

+----------+---------+----------+--------+---------+--------+--------+

Version- <b> <b>

Year

+----------+---------+----------+--------+---------+--------+--------+

Annex B. IANA Registration for image/tiff Application Parameter

Values used for facsimile

To: IANA@isi.edu

Subject: Registration of new Application parameter values for

image/tiff

MIME media type name: image/tiff

Optional parameters: Application

New Value(s): faxbw, faxcolor

Description of Use:

faxbw - The "faxbw" application parameter 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.

The definition of the use of this value is contained in Section 9 of

this document (TIFFPLUS).

Faxcolor - The "faxcolor" application parameter is suitable for use

by applications that can process one or more TIFF for facsimile

profiles or subsets that can be used for the encoding of black and

white, AND color facsimile data. The definition of the use of this

value is contained in Section 9 of this document (TIFFPLUS).

Security Considerations:

Security considerations related to use of the TIFF subsets described

by the "faxbw" and "faxcolor" values of the Application parameter are

identified in Section 10 of this document (TIFFPLUS).

Persons & email addresses to contact for further information:

Glenn W. Parsons (Glenn.Parsons@Nortel.ca)

James Rafferty (Jrafferty@worldnet.att.net)

Stephen Zilles (szilles@adobe.com)

Change Controller: Stephen Zilles

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.

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.

 
 
 
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