SIST ISO 12639:2002
(Main)Graphic technology -- Prepress digital data exchange -- Tag image file format for image technology (TIFF/IT)
Graphic technology -- Prepress digital data exchange -- Tag image file format for image technology (TIFF/IT)
Technologie graphique -- Échange de données numériques de préimpression -- Format de fichier d'image d'étiquette pour la technologie d'image
Grafična tehnologija - Izmenjava digitalnih podatkov v grafični pripravi - Slikovna tehnologija; slikovni format TIFF/IT
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INTERNATIONAL IS0
STANDARD 12639
First edition
1998-I O-01
Graphic technology - Prepress digital data
-Tag image file format for
exchange
image technology (TIFF/IT)
Technologie graphique - khange de don&es numkriques de
prkimpression - Format de fichier d ’image d ’etiquette pour la technologie
d ’image
Reference number
IS0 12639: 1998(E)
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IS0 12639: 1998(E)
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Contents
Page
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4 Terms, symbols, abbreviations, and field types . . . . . . . . . . . . . . . . . . . . . . . . 2
5 Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
6 Image data type description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Annexes
A Relationship between image types on a colour page . . . . . . . . . . . . . . . . . . . 27
B Colour values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
C The Tag Image File Format and TIFF/IT . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
D Final page (FP) file format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
E Identification and determination procedures . . . . . . . . . . . . . . . . . . . . . . . . . 34
F Examples of TIFF/IT-CT and TIFF/IT-CT/P1 files . . . . . . . . . . . . . . . . . . . 35
G Monochrome continuous tone picture colour value calculation . . . . . . . . . . 38
H Alphabetical list of TIFF/IT field names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
I
Background of the Pl (Profile 1) conformity level - TIFF/IT-P1 . . . . . . . . . 43
0 IS0 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-121 1 Geneve 20 l Switzerland
iso@ iso.ch
Internet
Printed in Switzerland
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0 IS0
IS0 12639:1998(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards bodies (IS0 member bodies). The work of preparing
International Standards is normally carried out through IS0 technical committees.
Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take
part in the work. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for voting. Publication as an International Standard requires
approval by at least 75 % of the member bodies casting a vote.
International Standard IS0 12639 was prepared by Technical Committee IS01
TC 130, Graphic technology.
Annexes A to I of this International Standard are for information only.
. . .
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IS0 12639: 1998(E)
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Introduction
This International Standard was prepared by Working Group 2 (Prepress data
exchange) of ISO/TC 130, Graphic technology, and is based on American National
Standard IT8.8- 1993, Graphic technology - Prepress digital data exchange - Tag
image file format for image technology (TIFF/IT).
.
The technical content of this International Standard enables the interchange of
various types of rasterised colour and monochrome image data files among
electronic, digital systems used in prepress image processing, graphic arts design
and related document creation and production operations. This International
Standard is intended for use as a media-independent means for such interchange,
thus is applicable to facilitate interchange through a variety of mechanisms such as,
though not limited to, network, magnetic and optical media.
The image data types supported by this International Standard include those
specified in IS0 10755: 1992, IS0 10756: 1993, IS0 10759: 1993 (Colour Picture
Data, Colour Line Art Data, and Monochrome Image Data) and also specified in
ANSI IT8.8-1993.
This International Standard, though based on ANSI IT8.8-1993, goes further to
specify a second, more constrained, level of conformity called Profile 1 (PI) for
each image data type. The Pl formats for CT (Colour Picture), MP (Monochrome
Picture), and BP (Binary Picture) files are compatible with the popular TIFF 6.0
files for CMYK (Separated) Images, Monochrome Images and Bilevel Images
respectively. The Pl formats for HC (High Resolution Continuous Tone), LW
(Line Art) and BL (Binary Line Art), though not compatible with TIFF 6.0, are
designed to be easier to implement within desktop systems by limiting the range of
options and selections. These Profile 1 formats allow for a broader usage of this
International Standard by allowing conformance to a simplified, restricted subset of
functionality supported by many popular application software systems used in the
prepress, graphic arts document processing and computer graphics and imaging
industries.
In support of backward compatibility, the IT8Header field provides the ability to
include, in TIFF/IT, unmodified headers (appended by an ASCII “null” at the end of
the character string) from IS0 10755, IS0 10756 and IS0 10759. This may be
particularly useful if a file is being transported from one IS0 10755, IS0 10756, or
IS0 10759 environment to another via TIFF/IT. TIFF/IT readers are not required to
interpret and use the contents of the ITSHeader field.
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IS0 12639: 1998(E)
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Graphic technology - Prepress digital data exchange - Tag image file
format for image technology (TIFF/IT)
data exchange - Monochrome image data on magnetic
1 Scope
tape.
This International Standard specifies a media-independent
IS0 1264 1: 1997, Graphic technology - Prepress digital
means for prepress electronic data exchange. This
data exchange - Colour targets-for input scanner
International Standard defines image file formats for
calibration.
encoding colour continuous tone picture images, colour
line art images, high resolution continuous tone images,
IS0 12642: 1996, Graphic technology - Prepress digital
monochrome continuous tone picture images, binary
- Input data for characterisation of 4 -
data exchange
.
picture images, and binary line art images.
colour process printing.
ANSI CGATS. 15: ‘), Graphic technology - Prepress
2 Normative references
digital data exchange - Three-component color data
definitions.
The following normative documents contain provisions
which, through reference in this text, constitute provisions
TIFF, Revision 6.0 Final: Aldus Corporation (now Adobe
of this International Standard. For dated references,
Systems Incorporated), June 3, 1992.
subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements
based on this International Standard are encouraged to
3 Definitions
investigate the possibility of applying the most recent
editions of the normative documents indicated below. For
For the purposes of this International Standard, the
undated references, the latest edition of the normative
following definitions apply.
document referred to applies. Members of IS0 and IEC
maintain registers of currently valid International
3.1 big-endian (byte-ordering): Method for arranging the
Standards.
sequence of the bytes within a SHORT or LONG from the
most significant to the least significant byte, as the byte
ISO/IEC 646: 1991, Information technology - IS0 7-bit
address increases.
coded character set,for information interchange.
3.2 little-endian (byte-ordering): Method for arranging
IS0 3166: 1993, Codes.for the representation of names qf
.
the sequence of the bytes within a SHORT or LONG from
countries.
the least significant to the most significant byte, as the byte
address increases.
IS0 10755: 1992, Graphic technology - Prepress digital
data exchange - Colour picture data on magnetic tape.
3.3 offset: Address within a TIFF/IT file, relative to byte
zero of the file.
IS0 10756: 1994, Graphic technology - Prepress digital
data exchange - Colour line art data on magnetic tape.
3.4 offset value: SHORT or LONG value within a
TIFF/IT file, containing the offset of a data element.
IS0 10759: 1994, Graphic technology - Prepress digital
1
1) To be published.
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IS0 12639: 1998(E)
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3.5 pixel: A picture element, the smallest single building 3.14 trapping: Technique for modifying colour
block of a picture containing colour identification and size separations to account for dimensional variations in the
(when used to describe dimensions relating to the picture printing process by overprinting in selected colours at the
resolution, as in pixels per inch).
boundaries between colours which might inadvertently be
left uncoloured by normal errors in printing press
3.6 printing tone value; printing dot value (of a data registration.
set): Number, recorded as data in the computer,
3.15 word-aligned: Sequence of bytes beginning at an
corresponding to the percentage area on a printing forme
that is intended to accept ink for transfer to the final sheet. even offset.
NOTE 1 This corresponds to the tone value of a half-tone film.
3.16 writer: An application, system or subsystem that
The light end of the final reproduction scale (highlights) will have
generates a file based on predetermined criteria and
values approaching 0% (or often in computer files, 0) and the dark
prepares the file for output.
end of the scale (shadows) will have values approaching 100% (or
often in computer files, 255).
4 Notations, symbols, abbreviations and field
3.7 reader: An application, system or subsystem that
types
accepts a file as its input and performs a level of processing
on that file that, at the minimum, accepts or rejects the file
4.1 Notations
based on predetermined criteria and, if accepted, passes the
file to the next stage of processing.
All numeric values in this International Standard are
expressed in decimal notation, unless otherwise indicated.
3.8 run length encoding: Data encoding method in which
A letter “h” is suffixed to indicate a hexadecimal value.
a sequence of data items, which may include many adjacent
Literal strings are denoted in this International Standard by
repetitions of the same value, is represented by a sequence
enclosing them in single quotation marks. In the
of ordered pairs, each consisting of a value and a repeat
descriptions of file parameters, field names from IS0
count.
10755, IS0 10756, and IS0 10759 are enclosed in
brackets.
NOTE 2 Run length encoding may result in data compression.
Preferred values in TIFF/IT fields are preceded by “=” and
3.9 separations: Individual planes of data that correspond
enclosed in parentheses, for example “(=5) “. Preferred
to each of the single colours to be used in the rendering
values are those values which are required to be accepted
process. For “process” colours these are cyan (C), magenta
and recognized by a compliant application or reader. A
(M), yellow (Y), and black (K). Additional separations are
compliant application or writer may write values other
often required for spot or speciality colours or for
than preferred values but the reader is not required to
imagewise finishing treatments such as varnish.
accept or recognize the value. It is left to the discretion of
the reader.
3.10 string: Serial sequence of characters, bytes, integers,
etc.
Required values in TIFF/IT fields are preceded by I ’=” but
not enclosed in parentheses, for example “=5 ”. Required
3.11 TIFF/IT field, TIFF field: A one-dimensional array
values are those values which are required to be written by
of values (though most are a single-entry array) having an
a compliant application or writer and are required to be
associated count.
accepted and recognized by a compliant application or
reader.
NOTE 3 An array is identified by a Field name, a Tag number,
and a Field type.
Default values, if specified, are preceded by “Default =” or
“d= “, for example “Default = 0,255 ”. In some tables,
3.12 TIFF/IT tag: A unique numeric identifier for each
default values are indicated in a “default value” column.
entry in the TIFF/IT file.
The reader shall assume the default value if no value is
written by the writer in the default-specified field.
3.13 transparent colour: Attribute that signifies that the
Because the default values shown for all “TIFF” tag
underlying image (if any) shows through.
numbers are those specified for TIFF files, they may not be
NOTE 4 A clear run is where no colour is present and the valid for the particular TIFF/IT file type. In all such cases,
underlying image (if any) shows through. The colour “white”
a mandatory field value or values is specified.
signifies that no underlying image should show through, only the
underlying substrate (paper). The “transparent” attribute may be
NOTE 5 When an entry is made in a “default value” column it
applied to any or all separations of a pixel run or a palette colour
might reference a TIFF 6.0 default value that may not be a valid
in a LW, HC, BL or BP file.
value for the particular TIFF/IT file type. This is usually
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IS0 12639: 1998(E)
indicated by entry of a mandatory field value or values in the
Pl Profile 1
tables.
TIFF Tag Image File Format , Version 6.0, Aldus
Classification marks used in clause 7 are defined as
Corporation.
follows:
m Mandatory (Absolute Requirement) field
TIFF/IT TIFF for image technology
The writer is required to include mandatory fields.
The reader is required to read and process the field.
NOTE 6 For character strings, it is recommended that only
The reader is allowed to reject those files where character values 32- 126 be used and to assume letters A-Z and a-z
have the same significance respectively.
mandatory fields are omitted.
4.3 Field types
opt, o Optional field
The writer may include or omit optional fields. The
reader is not required to read or process optional The field types used in this International Standard are as
follows:
fields.
ASCII: A field type consisting of a byte containing a
d Default field
The writer may include or omit default fields. The graphic character code from IS0 646. The
reader shall assume the default value for the field if last character in an ASCII string shall be a
the field is omitted. The reader is required to read “null” (character O/O).
and process the field when it contains any required
BYTE: A field type consisting of an 8-bit unsigned
or preferred values.
binary integer.
These classifications may vary by file type, and are
discussed further in clause 7. LONG: . A field type consisting of a 32-bit unsigned
binary integer.
Image File Directory (IFD) entries are identified by a field
RATIONAL: A field type consisting of two LONGS, the
name of one or more words, written with initial capital
first representing the numerator of a fraction
letters, and no internal spaces (e.g. “PageName ”).
and the second its denqminator.
4.2 Symbols and abbreviations
SHORT: A field type consisting of a 16-bit unsigned
binary integer.
The following symbols and abbreviations are used within
this International Standard with the meanings indicated:
BL binary line art (or run length encoded bitmap) 5 Conformance
image or file
This International Standard has two levels of conformance:
BP binary picture (or byte-packed bitmap) image or TIFF/IT (also referred to as full TIFF/IT) conformance and
file TIFF/IT-P1 conformance. Both conformance levels are
intended to support a media-independent means for the
CEPS Colour Electronic Prepress System exchange of various images used in the prepress, printing,
graphic arts, and information processing fields. TIFF/IT-
CT colour continuous tone picture image or file PI conformance provides a minimized set of options to
permit simpler implementation and compatibility, where
DDES Digital Data Exchange Specification possible (for CT, BP, and MP files), with commonly
available TIFF 6.0 readers and writers. TIFF/IT-P1 is
DTP Desktop Publishing intended for use where the full set of TIFF/IT options is not
required.
HC high resolution continuous tone (colour) image
Only TIFF/IT fields defined in this International Standard
or file
need to be written, recognized and interpreted by
IFD image file directory conforming implementations. TIFF fields that are
unclassified or not referred to in this International Standard
LW colour line art (or line work) image or file are not required to be supported for an implementation to
conform to this International Standard. If an unsupported
MP monochrome continuous tone picture image or field is read, processing of that field is at the discretion of
file the reader. The reader shall follow the strategy described
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IS0 12639: 1998(E)
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in TIFF and attempt to process the file while ignoring clause 7. Conformance with a specific image file type or
unsupported fields. (See annex I.) types requires identification of the specific image file type
using the identification defined in 5.1 with the designation
This International Standard specifies conforming TIFF/IT
YPl” appended (e.g. TIFF/IT-CT/PI).
and/or TIFF/IT-PI files for specific image data types. Files
for each specific image data type that conform to the
5.4 Conformance identification
requirements of this International Standard shall be
considered conforming TIFF/IT and/or TIFF/IT-P1 files for
Conformance with the provisions of this International
the specific image data type. Readers that accept and
Standard shall be identified individually for files, readers,
process these files shall be considered conforming TIFF/IT
and writers. The accepted terminology shall be the image
or TIFF/IT-P1 readers for the specific image data types.
file type followed by the designation “file ”, “reader ”, or
Writers that generate and output these files shall be
“writer” (e.g. TIFF/IT writer, TIFF/IT-CT/PI reader,
considered conforming TIFF/IT or TIFF/IT-P1 writers for
TIFF/IT-LW file).
the specific image data types. Where requirements of this
International Standard and TIFF 6.0 are in conflict, this
International Standard shall take precedence.
6 Image data type description
5.1 Image file type identification
6.1 Colour continuous tone picture image (CT)
data
TIFF/IT provides the ability to represent the data structure
of a wide range of printing and graphic arts images. The
A colour continuous tone picture image (CT) is a
identification of the individual image file types is as
rectangular array of pixels (picture elements). A pixel is
follows (see annex E):
represented by a set of values corresponding to its colour
components.
TIFF/IT-CT colour continuous tone picture image data
TIFF/IT-LW colour line art image data
NOTE 7 Pixels typically consist of four bytes, representing cyan
TIFF/IT-HC high resolution continuous tone image data
(C), magenta (M), yellow (Y), and black (K) process colours.
TIFF/IT-MP monochrome continuous tone picture image
data
6.2 Colour line art (LW) image data
TIFF/IT-BP binary picture image data
TIFF/IT-BL binary line art image data
A colour line art or line work (LW) image is a rectangular
array of pixels. Each pixel is one of a limited number of
5.2 TIFF/IT conformance
colours. The colours are defined in a palette table which
specifies the values of the colour separation components
For conformance to this International Standard, all image
for each entry in the palette. Line work images have areas
file types do not have to be implemented. Each image file
of many pixels of the same palette entry. Run length
type described in clause 7 may be individually
encoding techniques are used. Underlying images may be
implemented. Files, readers or writers may be identified as
made visible by the use of a transparent colour capability.
conforming for either all image file types or specifically
Colour line art images are normally of higher resolution
identified image file types.
than colour continuous tone picture images (CT).
Conformance with TIFF/IT requires implementation of the
6.3 High resolution continuous tone (HC) image
requirements for all image file types as described in clause
data
7. Conformance with a specific image file type or types
requires identification of the specific image file type using
A high resolution continuous tone (HC) image is a
the identification defined in 5.1 (e.g. TIFF/IT-CT).
rectangular array of pixels. A pixel is represented by a set
of values corresponding to its colour components. It is
5.3 TIFF/IT-P1 conformance
typically at the higher resolution of colour line art. It is
also characterized by a transparent colour capability and
TIFF/IT-P1 conformance provides an ability to represent
run length encoded similar to colour line art. It does not use
the data structure of various images in as simple and
a palette table and as such does not have the same limited
straightforward a way as possible in order to support image
colour representation of colour line art. High resolution
file exchange with prepress, printing, graphic arts, and
continuous tone images are typically used to define the
information processing systems and applications. TIFF/IT-
edges between merged colour continuous tone picture
Pl is a subset of TIFF/IT.
images, and between colour line art and colour continuous
tone picture images.
Conformance with TIFF/IT-PI requires implementation of
the requirements for all image file types as described in
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NOTE 8 Annex A describes the relationship between CT, LW,
7.1 Structure of TIFF/IT file
and HC images. Annex D describes an additional data type called
Final Page (FP) which describes a completed page.
This International Standard incorporates the notation and
structure as defined in TIFF 6.0 Sections 1 and 2. In
6.4 Monochrome and binary images
addition, those TIFF tags identified but not defined in this
International Standard shall be as defined in TIFF 6.0.
In addition to the colour formats specified in 6.1, 6.2, and
Where requirements of this International Standard and
6.3, monochrome continuous tone and binary DDES
TIFF 6.0 are in conflict, this International Standard shall
images are also supported. These images are similar to
take precedence.
their colour counterparts, except that their formats take
advantage of the reduced amount of data associated with
7.1.1 Overview
monochrome (single colour) and binary images.
A TIFF/IT file conveys image data for a single image or a
6.4.1 Monochrome continuous tone picture image (MP)
set of related images. The TIFF/IT structure includes a
data
short header, one or more Image File Directories (IFD),
and the image data associated with the IFDs. Image
A monochrome continuous tone picture image (MP)
parameters are encoded in tagged fields in the IFD. Fields
consists of a rectangular array of pixels. Each pixel is
that are not used to describe an image are omitted from its
represented by a single byte value indicating the varying
IFD. Each field is identified by its tag value rather than its
intensity of the single image colour at that pixel location.
position in the directory entry.
The intended effect is to reproduce the monochrome
continuous tone picture using various levels of the
7.1.2 Header
specified image colour.
A TIFF/IT file begins with an eight-byte image file header.
The monochrome continuous tone picture format is similar
to, though not identical to, a monochrome version of the
Bytes O-l : The pair of bytes at offset 0 of the file contains
colour continuous tone picture format with a single colour
the IS0 646 characters “11” (4949h) or “MM”
per pixel and is therefore not interleaved.
(4D4Dh). “II” signifies that the file is stored in
little-endian byte order. “MM” signifies that
6.4.2 Binary picture image (BP) data
the file is stored in big-endian byte order. A
writer may write either of the two byte orders.
A binary picture image (BP) consists of a rectangular array
A reader shall interpret both byte orders.
of pixels. Each pixel is represented by a single bit value
indicating that the pixel location is to be part of the
NOTE 9 In normal TIFF usage, this parameter applies to all data
background (bit value 0) or part of the image (bit value 1)
within headers , directories, and image data. In this International
for that pixel location. The bits are ordered left to right Standard, certain 16-bit fields in the image data have a fixed “big-
endian” byte order which will be defined with the specific image
within the byte; i.e. the most significant bit first. A
data types in clause 7.3 through 7.8.
background and a foreground colour may each be
specified.
Bytes 2-3: The pair of bytes (SHORT) at offset 2 contains
the constant 42 (2Ah).
6.4.3 Binary line art image (BL) data
Bytes 4-7: The four bytes (LONG) at offset 4 contain the
A binary line art image (BL) consists of a rectangular array
offset of the first IFD of the file. The directory
of pixels. Each pixel is represented by a single value which
is required to begin on a word-aligned
is encoded as a sequence of pairs of background and image
boundary.
colours.
7.1.3 Image subfiles
The binary line art image is further characterized by having
continuous areas of many pixels of image and background
A TIFF/IT file contains one or more subfiles, each
colour. Run length encoding techniques are used.
representing a single image which may be among a set of
related images in the same TIFF/IT file. Each subfile
consists of an Image File Directory (In>) together with one
7 Requirements
or more referenced word-aligned sequences containing
image data.
The format of the TIFF/IT and TIFF/IT-PI image data files
and the specific requirements for each of the individual
image file types follow. See annex F for examples of the
structure of these files.
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IS0 12639:1998(E)
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The offsets of the word-aligned sequences containing the
7.1.4 PFD (Image File Directory)
image data for each strip are contained in the data values of
Each IFD is located at an arbitrary word-aligned offset the mandatory StripOffsets field (tag 273, LONG or
within the file. The IFDs are forward-chained together. SHORT, count = StripsPerlmage) .
An IFD consists of a two-byte count of the quantity of IFD
entries within it, one or more IFD entries sorted in The StripByteCounts field (tag 279, LONG or SHORT,
ascending order of tag number, and a four-byte offset to the Count = StripsPerlmage) specifies the number of bytes for
each strip.
next IFD in the chain (zero in the case of the last IFD in the
file). Each IFD entry is a 12-byte field, describing a one-
parameter field that defines an attribute of the file. The structure of a TIFF/IT file containing a single image
subfile is shown in figure 1.
7.1.5 IFD entry
7.2 General parameters
Each IFD entry consists of a SHORT (two-byte) tag
number identifying the field, a SHORT (two-byte) data
This subclause describes, in general terms, each of the
type identifying the field type, a LONG (four-byte) count, fields used in TIFF/IT files. For usage specific to an image
and a LONG (four-byte) offset value. The offset value
file type (i.e. CT, LW, HC, MP, BP, and BL) see the
shall be an even number since the value is expected to be
subclause appropriate to that file type. Annex H provides
on a 16-bit word boundary.
an alphabetical listing of TIFF/IT fields.
The field type codes are: 7.2.1 Job identification
1 BYTE
The job and picture name of the image are described by the
2 ASCII
document name (DocumentName) and image description
3 SHORT
(ImageDescription) fields. The page name (PageName)
4 LONG
field may also be used. Annex H contains an alphabetical
5 RATIONAL
list of TIFF/IT fields.
The count determines the number of data elements in the 269 DocumentName ASCII [Job Name]
value. The count of an ASCII string entry shall be the 270 ImageDescription ASCII [Picture Name, Image
number of characters (bytes) in the string, including the Name]
terminating null character.
285 PageName ASCII
NOTE 10 In the case of an ASCII string, the IS0 10755, IS0
The originator of the image may be identified, and a
10756, and IS0 10759 headers do not have a terminating null,
copyright statement may be inclu
...
SLOVENSKI STANDARD
SIST ISO 12639:2002
01-november-2002
*UDILþQDWHKQRORJLMD,]PHQMDYDGLJLWDOQLKSRGDWNRYYJUDILþQLSULSUDYL6OLNRYQD
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Graphic technology -- Prepress digital data exchange -- Tag image file format for image
technology (TIFF/IT)
Technologie graphique -- Échange de données numériques de préimpression -- Format
de fichier d'image d'étiquette pour la technologie d'image
Ta slovenski standard je istoveten z: ISO 12639:1998
ICS:
35.240.30 Uporabniške rešitve IT v IT applications in information,
informatiki, dokumentiranju in documentation and
založništvu publishing
37.100.99 'UXJLVWDQGDUGLY]YH]L] Other standards related to
JUDILþQRWHKQRORJLMR graphic technology
SIST ISO 12639:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 12639:2002
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SIST ISO 12639:2002
INTERNATIONAL IS0
STANDARD 12639
First edition
1998-I O-01
Graphic technology - Prepress digital data
-Tag image file format for
exchange
image technology (TIFF/IT)
Technologie graphique - khange de don&es numkriques de
prkimpression - Format de fichier d ’image d ’etiquette pour la technologie
d ’image
Reference number
IS0 12639: 1998(E)
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SIST ISO 12639:2002
IS0 12639: 1998(E)
0 IS0
Contents
Page
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4 Terms, symbols, abbreviations, and field types . . . . . . . . . . . . . . . . . . . . . . . . 2
5 Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
6 Image data type description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Annexes
A Relationship between image types on a colour page . . . . . . . . . . . . . . . . . . . 27
B Colour values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
C The Tag Image File Format and TIFF/IT . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
D Final page (FP) file format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
E Identification and determination procedures . . . . . . . . . . . . . . . . . . . . . . . . . 34
F Examples of TIFF/IT-CT and TIFF/IT-CT/P1 files . . . . . . . . . . . . . . . . . . . 35
G Monochrome continuous tone picture colour value calculation . . . . . . . . . . 38
H Alphabetical list of TIFF/IT field names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
I
Background of the Pl (Profile 1) conformity level - TIFF/IT-P1 . . . . . . . . . 43
0 IS0 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-121 1 Geneve 20 l Switzerland
iso@ iso.ch
Internet
Printed in Switzerland
ii
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IS0 12639:1998(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards bodies (IS0 member bodies). The work of preparing
International Standards is normally carried out through IS0 technical committees.
Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take
part in the work. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for voting. Publication as an International Standard requires
approval by at least 75 % of the member bodies casting a vote.
International Standard IS0 12639 was prepared by Technical Committee IS01
TC 130, Graphic technology.
Annexes A to I of this International Standard are for information only.
. . .
111
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Introduction
This International Standard was prepared by Working Group 2 (Prepress data
exchange) of ISO/TC 130, Graphic technology, and is based on American National
Standard IT8.8- 1993, Graphic technology - Prepress digital data exchange - Tag
image file format for image technology (TIFF/IT).
.
The technical content of this International Standard enables the interchange of
various types of rasterised colour and monochrome image data files among
electronic, digital systems used in prepress image processing, graphic arts design
and related document creation and production operations. This International
Standard is intended for use as a media-independent means for such interchange,
thus is applicable to facilitate interchange through a variety of mechanisms such as,
though not limited to, network, magnetic and optical media.
The image data types supported by this International Standard include those
specified in IS0 10755: 1992, IS0 10756: 1993, IS0 10759: 1993 (Colour Picture
Data, Colour Line Art Data, and Monochrome Image Data) and also specified in
ANSI IT8.8-1993.
This International Standard, though based on ANSI IT8.8-1993, goes further to
specify a second, more constrained, level of conformity called Profile 1 (PI) for
each image data type. The Pl formats for CT (Colour Picture), MP (Monochrome
Picture), and BP (Binary Picture) files are compatible with the popular TIFF 6.0
files for CMYK (Separated) Images, Monochrome Images and Bilevel Images
respectively. The Pl formats for HC (High Resolution Continuous Tone), LW
(Line Art) and BL (Binary Line Art), though not compatible with TIFF 6.0, are
designed to be easier to implement within desktop systems by limiting the range of
options and selections. These Profile 1 formats allow for a broader usage of this
International Standard by allowing conformance to a simplified, restricted subset of
functionality supported by many popular application software systems used in the
prepress, graphic arts document processing and computer graphics and imaging
industries.
In support of backward compatibility, the IT8Header field provides the ability to
include, in TIFF/IT, unmodified headers (appended by an ASCII “null” at the end of
the character string) from IS0 10755, IS0 10756 and IS0 10759. This may be
particularly useful if a file is being transported from one IS0 10755, IS0 10756, or
IS0 10759 environment to another via TIFF/IT. TIFF/IT readers are not required to
interpret and use the contents of the ITSHeader field.
iv
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Graphic technology - Prepress digital data exchange - Tag image file
format for image technology (TIFF/IT)
data exchange - Monochrome image data on magnetic
1 Scope
tape.
This International Standard specifies a media-independent
IS0 1264 1: 1997, Graphic technology - Prepress digital
means for prepress electronic data exchange. This
data exchange - Colour targets-for input scanner
International Standard defines image file formats for
calibration.
encoding colour continuous tone picture images, colour
line art images, high resolution continuous tone images,
IS0 12642: 1996, Graphic technology - Prepress digital
monochrome continuous tone picture images, binary
- Input data for characterisation of 4 -
data exchange
.
picture images, and binary line art images.
colour process printing.
ANSI CGATS. 15: ‘), Graphic technology - Prepress
2 Normative references
digital data exchange - Three-component color data
definitions.
The following normative documents contain provisions
which, through reference in this text, constitute provisions
TIFF, Revision 6.0 Final: Aldus Corporation (now Adobe
of this International Standard. For dated references,
Systems Incorporated), June 3, 1992.
subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements
based on this International Standard are encouraged to
3 Definitions
investigate the possibility of applying the most recent
editions of the normative documents indicated below. For
For the purposes of this International Standard, the
undated references, the latest edition of the normative
following definitions apply.
document referred to applies. Members of IS0 and IEC
maintain registers of currently valid International
3.1 big-endian (byte-ordering): Method for arranging the
Standards.
sequence of the bytes within a SHORT or LONG from the
most significant to the least significant byte, as the byte
ISO/IEC 646: 1991, Information technology - IS0 7-bit
address increases.
coded character set,for information interchange.
3.2 little-endian (byte-ordering): Method for arranging
IS0 3166: 1993, Codes.for the representation of names qf
.
the sequence of the bytes within a SHORT or LONG from
countries.
the least significant to the most significant byte, as the byte
address increases.
IS0 10755: 1992, Graphic technology - Prepress digital
data exchange - Colour picture data on magnetic tape.
3.3 offset: Address within a TIFF/IT file, relative to byte
zero of the file.
IS0 10756: 1994, Graphic technology - Prepress digital
data exchange - Colour line art data on magnetic tape.
3.4 offset value: SHORT or LONG value within a
TIFF/IT file, containing the offset of a data element.
IS0 10759: 1994, Graphic technology - Prepress digital
1
1) To be published.
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3.5 pixel: A picture element, the smallest single building 3.14 trapping: Technique for modifying colour
block of a picture containing colour identification and size separations to account for dimensional variations in the
(when used to describe dimensions relating to the picture printing process by overprinting in selected colours at the
resolution, as in pixels per inch).
boundaries between colours which might inadvertently be
left uncoloured by normal errors in printing press
3.6 printing tone value; printing dot value (of a data registration.
set): Number, recorded as data in the computer,
3.15 word-aligned: Sequence of bytes beginning at an
corresponding to the percentage area on a printing forme
that is intended to accept ink for transfer to the final sheet. even offset.
NOTE 1 This corresponds to the tone value of a half-tone film.
3.16 writer: An application, system or subsystem that
The light end of the final reproduction scale (highlights) will have
generates a file based on predetermined criteria and
values approaching 0% (or often in computer files, 0) and the dark
prepares the file for output.
end of the scale (shadows) will have values approaching 100% (or
often in computer files, 255).
4 Notations, symbols, abbreviations and field
3.7 reader: An application, system or subsystem that
types
accepts a file as its input and performs a level of processing
on that file that, at the minimum, accepts or rejects the file
4.1 Notations
based on predetermined criteria and, if accepted, passes the
file to the next stage of processing.
All numeric values in this International Standard are
expressed in decimal notation, unless otherwise indicated.
3.8 run length encoding: Data encoding method in which
A letter “h” is suffixed to indicate a hexadecimal value.
a sequence of data items, which may include many adjacent
Literal strings are denoted in this International Standard by
repetitions of the same value, is represented by a sequence
enclosing them in single quotation marks. In the
of ordered pairs, each consisting of a value and a repeat
descriptions of file parameters, field names from IS0
count.
10755, IS0 10756, and IS0 10759 are enclosed in
brackets.
NOTE 2 Run length encoding may result in data compression.
Preferred values in TIFF/IT fields are preceded by “=” and
3.9 separations: Individual planes of data that correspond
enclosed in parentheses, for example “(=5) “. Preferred
to each of the single colours to be used in the rendering
values are those values which are required to be accepted
process. For “process” colours these are cyan (C), magenta
and recognized by a compliant application or reader. A
(M), yellow (Y), and black (K). Additional separations are
compliant application or writer may write values other
often required for spot or speciality colours or for
than preferred values but the reader is not required to
imagewise finishing treatments such as varnish.
accept or recognize the value. It is left to the discretion of
the reader.
3.10 string: Serial sequence of characters, bytes, integers,
etc.
Required values in TIFF/IT fields are preceded by I ’=” but
not enclosed in parentheses, for example “=5 ”. Required
3.11 TIFF/IT field, TIFF field: A one-dimensional array
values are those values which are required to be written by
of values (though most are a single-entry array) having an
a compliant application or writer and are required to be
associated count.
accepted and recognized by a compliant application or
reader.
NOTE 3 An array is identified by a Field name, a Tag number,
and a Field type.
Default values, if specified, are preceded by “Default =” or
“d= “, for example “Default = 0,255 ”. In some tables,
3.12 TIFF/IT tag: A unique numeric identifier for each
default values are indicated in a “default value” column.
entry in the TIFF/IT file.
The reader shall assume the default value if no value is
written by the writer in the default-specified field.
3.13 transparent colour: Attribute that signifies that the
Because the default values shown for all “TIFF” tag
underlying image (if any) shows through.
numbers are those specified for TIFF files, they may not be
NOTE 4 A clear run is where no colour is present and the valid for the particular TIFF/IT file type. In all such cases,
underlying image (if any) shows through. The colour “white”
a mandatory field value or values is specified.
signifies that no underlying image should show through, only the
underlying substrate (paper). The “transparent” attribute may be
NOTE 5 When an entry is made in a “default value” column it
applied to any or all separations of a pixel run or a palette colour
might reference a TIFF 6.0 default value that may not be a valid
in a LW, HC, BL or BP file.
value for the particular TIFF/IT file type. This is usually
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indicated by entry of a mandatory field value or values in the
Pl Profile 1
tables.
TIFF Tag Image File Format , Version 6.0, Aldus
Classification marks used in clause 7 are defined as
Corporation.
follows:
m Mandatory (Absolute Requirement) field
TIFF/IT TIFF for image technology
The writer is required to include mandatory fields.
The reader is required to read and process the field.
NOTE 6 For character strings, it is recommended that only
The reader is allowed to reject those files where character values 32- 126 be used and to assume letters A-Z and a-z
have the same significance respectively.
mandatory fields are omitted.
4.3 Field types
opt, o Optional field
The writer may include or omit optional fields. The
reader is not required to read or process optional The field types used in this International Standard are as
follows:
fields.
ASCII: A field type consisting of a byte containing a
d Default field
The writer may include or omit default fields. The graphic character code from IS0 646. The
reader shall assume the default value for the field if last character in an ASCII string shall be a
the field is omitted. The reader is required to read “null” (character O/O).
and process the field when it contains any required
BYTE: A field type consisting of an 8-bit unsigned
or preferred values.
binary integer.
These classifications may vary by file type, and are
discussed further in clause 7. LONG: . A field type consisting of a 32-bit unsigned
binary integer.
Image File Directory (IFD) entries are identified by a field
RATIONAL: A field type consisting of two LONGS, the
name of one or more words, written with initial capital
first representing the numerator of a fraction
letters, and no internal spaces (e.g. “PageName ”).
and the second its denqminator.
4.2 Symbols and abbreviations
SHORT: A field type consisting of a 16-bit unsigned
binary integer.
The following symbols and abbreviations are used within
this International Standard with the meanings indicated:
BL binary line art (or run length encoded bitmap) 5 Conformance
image or file
This International Standard has two levels of conformance:
BP binary picture (or byte-packed bitmap) image or TIFF/IT (also referred to as full TIFF/IT) conformance and
file TIFF/IT-P1 conformance. Both conformance levels are
intended to support a media-independent means for the
CEPS Colour Electronic Prepress System exchange of various images used in the prepress, printing,
graphic arts, and information processing fields. TIFF/IT-
CT colour continuous tone picture image or file PI conformance provides a minimized set of options to
permit simpler implementation and compatibility, where
DDES Digital Data Exchange Specification possible (for CT, BP, and MP files), with commonly
available TIFF 6.0 readers and writers. TIFF/IT-P1 is
DTP Desktop Publishing intended for use where the full set of TIFF/IT options is not
required.
HC high resolution continuous tone (colour) image
Only TIFF/IT fields defined in this International Standard
or file
need to be written, recognized and interpreted by
IFD image file directory conforming implementations. TIFF fields that are
unclassified or not referred to in this International Standard
LW colour line art (or line work) image or file are not required to be supported for an implementation to
conform to this International Standard. If an unsupported
MP monochrome continuous tone picture image or field is read, processing of that field is at the discretion of
file the reader. The reader shall follow the strategy described
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in TIFF and attempt to process the file while ignoring clause 7. Conformance with a specific image file type or
unsupported fields. (See annex I.) types requires identification of the specific image file type
using the identification defined in 5.1 with the designation
This International Standard specifies conforming TIFF/IT
YPl” appended (e.g. TIFF/IT-CT/PI).
and/or TIFF/IT-PI files for specific image data types. Files
for each specific image data type that conform to the
5.4 Conformance identification
requirements of this International Standard shall be
considered conforming TIFF/IT and/or TIFF/IT-P1 files for
Conformance with the provisions of this International
the specific image data type. Readers that accept and
Standard shall be identified individually for files, readers,
process these files shall be considered conforming TIFF/IT
and writers. The accepted terminology shall be the image
or TIFF/IT-P1 readers for the specific image data types.
file type followed by the designation “file ”, “reader ”, or
Writers that generate and output these files shall be
“writer” (e.g. TIFF/IT writer, TIFF/IT-CT/PI reader,
considered conforming TIFF/IT or TIFF/IT-P1 writers for
TIFF/IT-LW file).
the specific image data types. Where requirements of this
International Standard and TIFF 6.0 are in conflict, this
International Standard shall take precedence.
6 Image data type description
5.1 Image file type identification
6.1 Colour continuous tone picture image (CT)
data
TIFF/IT provides the ability to represent the data structure
of a wide range of printing and graphic arts images. The
A colour continuous tone picture image (CT) is a
identification of the individual image file types is as
rectangular array of pixels (picture elements). A pixel is
follows (see annex E):
represented by a set of values corresponding to its colour
components.
TIFF/IT-CT colour continuous tone picture image data
TIFF/IT-LW colour line art image data
NOTE 7 Pixels typically consist of four bytes, representing cyan
TIFF/IT-HC high resolution continuous tone image data
(C), magenta (M), yellow (Y), and black (K) process colours.
TIFF/IT-MP monochrome continuous tone picture image
data
6.2 Colour line art (LW) image data
TIFF/IT-BP binary picture image data
TIFF/IT-BL binary line art image data
A colour line art or line work (LW) image is a rectangular
array of pixels. Each pixel is one of a limited number of
5.2 TIFF/IT conformance
colours. The colours are defined in a palette table which
specifies the values of the colour separation components
For conformance to this International Standard, all image
for each entry in the palette. Line work images have areas
file types do not have to be implemented. Each image file
of many pixels of the same palette entry. Run length
type described in clause 7 may be individually
encoding techniques are used. Underlying images may be
implemented. Files, readers or writers may be identified as
made visible by the use of a transparent colour capability.
conforming for either all image file types or specifically
Colour line art images are normally of higher resolution
identified image file types.
than colour continuous tone picture images (CT).
Conformance with TIFF/IT requires implementation of the
6.3 High resolution continuous tone (HC) image
requirements for all image file types as described in clause
data
7. Conformance with a specific image file type or types
requires identification of the specific image file type using
A high resolution continuous tone (HC) image is a
the identification defined in 5.1 (e.g. TIFF/IT-CT).
rectangular array of pixels. A pixel is represented by a set
of values corresponding to its colour components. It is
5.3 TIFF/IT-P1 conformance
typically at the higher resolution of colour line art. It is
also characterized by a transparent colour capability and
TIFF/IT-P1 conformance provides an ability to represent
run length encoded similar to colour line art. It does not use
the data structure of various images in as simple and
a palette table and as such does not have the same limited
straightforward a way as possible in order to support image
colour representation of colour line art. High resolution
file exchange with prepress, printing, graphic arts, and
continuous tone images are typically used to define the
information processing systems and applications. TIFF/IT-
edges between merged colour continuous tone picture
Pl is a subset of TIFF/IT.
images, and between colour line art and colour continuous
tone picture images.
Conformance with TIFF/IT-PI requires implementation of
the requirements for all image file types as described in
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NOTE 8 Annex A describes the relationship between CT, LW,
7.1 Structure of TIFF/IT file
and HC images. Annex D describes an additional data type called
Final Page (FP) which describes a completed page.
This International Standard incorporates the notation and
structure as defined in TIFF 6.0 Sections 1 and 2. In
6.4 Monochrome and binary images
addition, those TIFF tags identified but not defined in this
International Standard shall be as defined in TIFF 6.0.
In addition to the colour formats specified in 6.1, 6.2, and
Where requirements of this International Standard and
6.3, monochrome continuous tone and binary DDES
TIFF 6.0 are in conflict, this International Standard shall
images are also supported. These images are similar to
take precedence.
their colour counterparts, except that their formats take
advantage of the reduced amount of data associated with
7.1.1 Overview
monochrome (single colour) and binary images.
A TIFF/IT file conveys image data for a single image or a
6.4.1 Monochrome continuous tone picture image (MP)
set of related images. The TIFF/IT structure includes a
data
short header, one or more Image File Directories (IFD),
and the image data associated with the IFDs. Image
A monochrome continuous tone picture image (MP)
parameters are encoded in tagged fields in the IFD. Fields
consists of a rectangular array of pixels. Each pixel is
that are not used to describe an image are omitted from its
represented by a single byte value indicating the varying
IFD. Each field is identified by its tag value rather than its
intensity of the single image colour at that pixel location.
position in the directory entry.
The intended effect is to reproduce the monochrome
continuous tone picture using various levels of the
7.1.2 Header
specified image colour.
A TIFF/IT file begins with an eight-byte image file header.
The monochrome continuous tone picture format is similar
to, though not identical to, a monochrome version of the
Bytes O-l : The pair of bytes at offset 0 of the file contains
colour continuous tone picture format with a single colour
the IS0 646 characters “11” (4949h) or “MM”
per pixel and is therefore not interleaved.
(4D4Dh). “II” signifies that the file is stored in
little-endian byte order. “MM” signifies that
6.4.2 Binary picture image (BP) data
the file is stored in big-endian byte order. A
writer may write either of the two byte orders.
A binary picture image (BP) consists of a rectangular array
A reader shall interpret both byte orders.
of pixels. Each pixel is represented by a single bit value
indicating that the pixel location is to be part of the
NOTE 9 In normal TIFF usage, this parameter applies to all data
background (bit value 0) or part of the image (bit value 1)
within headers , directories, and image data. In this International
for that pixel location. The bits are ordered left to right Standard, certain 16-bit fields in the image data have a fixed “big-
endian” byte order which will be defined with the specific image
within the byte; i.e. the most significant bit first. A
data types in clause 7.3 through 7.8.
background and a foreground colour may each be
specified.
Bytes 2-3: The pair of bytes (SHORT) at offset 2 contains
the constant 42 (2Ah).
6.4.3 Binary line art image (BL) data
Bytes 4-7: The four bytes (LONG) at offset 4 contain the
A binary line art image (BL) consists of a rectangular array
offset of the first IFD of the file. The directory
of pixels. Each pixel is represented by a single value which
is required to begin on a word-aligned
is encoded as a sequence of pairs of background and image
boundary.
colours.
7.1.3 Image subfiles
The binary line art image is further characterized by having
continuous areas of many pixels of image and background
A TIFF/IT file contains one or more subfiles, each
colour. Run length encoding techniques are used.
representing a single image which may be among a set of
related images in the same TIFF/IT file. Each subfile
consists of an Image File Directory (In>) together with one
7 Requirements
or more referenced word-aligned sequences containing
image data.
The format of the TIFF/IT and TIFF/IT-PI image data files
and the specific requirements for each of the individual
image file types follow. See annex F for examples of the
structure of these files.
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The offsets of the word-aligned sequences containing the
7.1.4 PFD (Image File Directory)
image data for each strip are contained in the data values of
Each IFD is located at an arbitrary word-aligned offset the mandatory StripOffsets field (tag 273, LONG or
within the file. The IFDs are forward-chained together. SHORT, count = StripsPerlmage) .
An IFD consists of a two-byte count of the quantity of IFD
entries within it, one or more IFD entries sorted in The StripByteCounts field (tag 279, LONG or SHORT,
ascending order of tag number, and a four-byte offset to the Count = StripsPerlmage) specifies the number of bytes for
each strip.
next IFD in the chain (zero in the case of the last IFD in the
file). Each IFD entry is a 12-byte field, describing a one-
parameter field that defines an attribute of the file. The structure of a TIFF/IT file containing a single image
subfile is shown in figure 1.
7.1.5 IFD entry
7.2 General parameters
Each IFD entry consists of a SHORT (two-byte) tag
number identifying the field, a SHORT (two-byte) data
This subclause describes, in general terms, each of the
type identifying the field type, a LONG (four-byte) count,
...
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