Document management applications -- Raster image transport and storage

This document defines a subset of ISO 32000 suitable for storage, transport and exchange of multi-page raster-image documents, including but not limited to scanned documents. Bitonal, grayscale and RGB images are supported. Compression options for image data streams include JPEG, CCITT Group 4 Fax and uncompressed.

Applications de gestion de documents -- Transport et stockage des images tramées

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07-Jul-2020
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6060 - International Standard published
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ISO 23504-1:2020 - Document management applications -- Raster image transport and storage
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INTERNATIONAL ISO
STANDARD 23504-1
First edition
2020-07
Corrected version
2020-09
Document management
applications — Raster image transport
and storage —
Part 1:
Use of ISO 32000 (PDF/R-1)
Applications de gestion de documents — Transport et stockage des
images tramées —
Partie 1: Utilisation de l'ISO 32000 (PDF/R-1)
Reference number
ISO 23504-1:2020(E)
ISO 2020
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ISO 23504-1:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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ISO 23504-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Notation ......................................................................................................................................................................................................................... 2

5 Version identification ...................................................................................................................................................................................... 2

6 Conformity requirements ........................................................................................................................................................................... 3

6.1 General ........................................................................................................................................................................................................... 3

6.2 PDF subset .................................................................................................................................................................................................. 3

6.2.1 General...................................................................................................................................................................................... 3

6.2.2 Unencrypted PDF/R files .......................................................................................................................................... 3

6.2.3 Encrypted PDF/R files................................................................................................................................................. 3

6.2.4 Unencrypted and encrypted PDF/R files .................................................................................................... 4

6.3 Catalog dictionary ................................................................................................................................................................................ 4

6.4 Metadata ....................................................................................................................................................................................................... 4

6.4.1 General...................................................................................................................................................................................... 4

6.4.2 Document level and page level metadata streams ............................................................................. 4

6.4.3 Document information dictionary .................................................................................................................... 5

6.4.4 XMP Metadata .................................................................................................................................................................... 5

6.5 Page objects ............................................................................................................................................................................................... 5

6.5.1 General...................................................................................................................................................................................... 5

6.5.2 Page tree nodes ................................................................................................................................................................. 5

6.5.3 Media box ............................................................................................................................................................................... 5

6.5.4 Annots array and digital signatures ................................................................................................................ 6

6.5.5 Resources dictionary .................................................................................................................................................... 6

6.5.6 Rotation ................................................................................................................................................................................... 6

6.5.7 Content stream .................................................................................................................................................................. 6

6.6 Strips ................................................................................................................................................................................................................ 7

6.6.1 General...................................................................................................................................................................................... 7

6.6.2 Bitonal images .................................................................................................................................................................... 7

6.6.3 Grayscale images ...................................................................... ........................................................................................ 8

6.6.4 RGB images ........................................................................................................................................................................... 8

6.7 Incremental updates .......................................................................................................................................................................... 9

6.8 Encryption .................................................................................................................................................................................................. 9

Annex A (informative) Application notes .....................................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................16

© ISO 2020 – All rights reserved iii
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ISO 23504-1:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO 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.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 171, Document management applications,

Subcommittee SC 2, Document file formats, EDMS systems and authenticity of information.

This corrected version of ISO 23504-1:2020 incorporates the following corrections:

— Angled brackets inserted around 'total height' in the numerator of the second formula in A.4;

— ']' added to the line before '/Whitepoint' in A.8.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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ISO 23504-1:2020(E)
Introduction

This document describes PDF/R (Raster), a strict subset of the PDF file format, for storing, transporting

and exchanging multi-page raster-image documents, especially scanned documents and photographs.

PDF/R provides the portability of PDF while offering the core functionality of TIFF. Bitonal, grayscale

and RGB images are supported. Compression options include JPEG, lossless CCITT Group 4 Fax and

uncompressed.

This document describes the restrictions that differentiate a PDF/R file from a standard PDF file.

Additionally, it specifies (see Clause 5) that a comment is used to identify files claiming to be PDF/R

files. There is no intention herein to claim any intellectual property that is not present in the existing

PDF standard, nor claim any IP that is covered therein.

PDF/R is intended to be a standard format for storing, transporting and exchanging scanned documents.

As a subset of PDF, it takes advantage of the widespread support for viewing, printing and processing

PDF files. As a narrowly restricted subset of PDF, it is much simpler to generate and interpret, allowing

it to replace the TIFF and JPEG file formats for capture and delivery of scanner output.

PDF/R imposes many restrictions on PDF content and layout, for the following benefits:

— files can be read and written without a full PDF parser or generator;
— files can be created efficiently from raster images;
— files can be generated using a fixed-size raster data buffer;
— images can be located and read efficiently with comparatively simple code;
— PDF/R files can be quickly and easily identified as such by software;
— PDF/R supports effective and readily available compression algorithms.

PDF/R has important advantages over the full PDF format for storing scanned documents:

— the raster image data can be recovered;
— a complex rendering engine is not required;

— it provides a precise, well-defined target, simplifying engineering design and testing.

PDF/R retains optional PDF security features useful for protecting content:

— encryption is allowed for implementations that need to protect document content at rest.

PDF/R retains optional PDF digital signature features useful for authenticating content:

— one or more digital signatures may be used for implementations that require verification of the

document origin, authenticity, date or time of creation, and so on.
PDF/R has important advantages over TIFF and JPEG for storing scanned documents:
— compared to TIFF, it has far fewer and simpler variants;

— compared to TIFF, compression is simpler and better standardized and supported;

— compared to TIFF, PDF files can be natively viewed and printed on more platforms;

— unlike JPEG, it is natively multi-page and handles bitonal images.

PDF/R was created by collaboration between the TWAIN Working Group, which originated the PDF/R

concept, and the PDF Association, which provided PDF technology expertise and perspective as well

as means of communicating with the PDF software industry to ensure a diverse range of relevant

viewpoints was represented.
© ISO 2020 – All rights reserved v
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INTERNATIONAL STANDARD ISO 23504-1:2020(E)
Document management applications — Raster image
transport and storage —
Part 1:
Use of ISO 32000 (PDF/R-1)
1 Scope

This document defines a subset of ISO 32000 suitable for storage, transport and exchange of multi-page

raster-image documents, including but not limited to scanned documents. Bitonal, grayscale and RGB

images are supported. Compression options for image data streams include JPEG, CCITT Group 4 Fax

and uncompressed.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 32000-1:2008, Document management — Portable document format — Part 1: PDF 1.7

ISO 32000-2 :2020, Document management — Portable document format — Part 2: PDF 2.0

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
page image
image of one side of a physical page (3.2)
3.2
physical page
physical media object with two sides
3.3
unencrypted PDF/R file

file conforming to this PDF/R specification that does not contain an Encrypt dictionary in the trailer

dictionary
3.4
encrypted PDF/R file

file conforming to this PDF/R specification that does contain an Encrypt dictionary in the trailer

dictionary
1) Under preparation. Stage at the time of publication: ISO DIS 32000-2.
© ISO 2020 – All rights reserved 1
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ISO 23504-1:2020(E)
4 Notation

PDF operators, PDF keywords, the names of keys in PDF dictionaries, and other predefined names are

written in bold font; operands of PDF operators or values of dictionary keys are written in italic font.

Some names can also be used as values, depending on the context, and so the styling of the content will

be context-specific.
EXAMPLE 1 The Sig value for the FT key.

Token characters used to delimit objects and describe the structure of PDF files, as defined in

ISO 32000-1:2008, 7.2.1, may be identified by their ISO/IEC 646-character name written in uppercase in

bold font followed by a parenthetic two-digit hexadecimal character value with the suffix “h”.

EXAMPLE 2 CARRIAGE RETURN (0Dh).

Text string characters, as defined in ISO 32000-1:2008, 7.9.2, may be identified by their ISO/IEC 10646

character name written in uppercase in bold font followed by a parenthetic four-digit hexadecimal

character code value with the prefix “U+”.
EXAMPLE 3 EN SPACE (U+2002).
5 Version identification

A PDF file conforming to the PDF/R specification is identified by one comment line near the end of the

file, immediately before the last occurrence of the line in the file containing the startxref key. The

comment shall be:
%PDF-raster-x.y
where
“x” (the digit before the decimal point) is the major version number
“y” (the digit after the decimal point) is the minor version number

The PDF/R version number for PDF files conforming to this document shall be 1.0. New major versions

may be incompatible with previous versions; new minor versions are expected to not break existing

readers.
This comment line marks the file as intended to conform to this specification.
EXAMPLE
trailer
/Info 58 0 R
/Size 59
/Root 1 0 R
/ID
[

%PDF-raster-1.0
startxref
177317
%%EOF
2) Under preparation. Stage at the time of publication: ISO/IEC DIS 10646.
2 © ISO 2020 – All rights reserved
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ISO 23504-1:2020(E)
6 Conformity requirements
6.1 General

A conforming PDF/R file shall conform to all requirements listed in 6.2, “PDF subset” to 6.8, “Encryption”.

6.2 PDF subset
6.2.1 General

Conformity of unencrypted and encrypted PDF/R files only differs regarding the use of encryption.

Encrypted PDF/R files make use of encryption features introduced in ISO 32000-2, and not available

in ISO 32000-1. The definition of, and the requirements for, any other feature allowed in a PDF/R file

do not differ between ISO 32000-1 and ISO 32000-2. For the sake of simplicity, all requirements for

PDF/R files, with the exception of those for the use of encryption, are specified on the background of

ISO 32000-1.
6.2.2 Unencrypted PDF/R files

A PDF/R-conforming file that is not encrypted shall adhere to all the requirements of ISO 32000-1 as

modified by this document.
The header shall be one of the following:
— “%PDF-1.4”;
— “%PDF-1.5”;
— “%PDF-1.6”;
— “%PDF-1.7”.

NOTE If the contents of the file are inconsistent with the version number in the header processing results

will be implementation dependent.
No filters other than the following shall be used in an unencrypted PDF/R file:
— FlateDecode;
— CCITTFaxDecode (only for bitonal images);
— DCTDecode (only for 8-bit grayscale or RGB images).
6.2.3 Encrypted PDF/R files

A PDF/R-conforming file that is encrypted shall adhere to all requirements of ISO 32000-1, as modified

by this document, with the following exceptions:
— the header shall be “%PDF-2.0”;

— the file shall adhere to all requirements of ISO 32000-2:2020, 7.6, “Encryption”, as modified by 6.8,

“Encryption”, in this document.
Only the following filters shall be allowed in an encrypted PDF/R file:
— FlateDecode;
— CCITTFaxDecode (only for bitonal images);
— DCTDecode (only for 8 bit grayscale or RGB images);
© ISO 2020 – All rights reserved 3
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ISO 23504-1:2020(E)
— Crypt.
6.2.4 Unencrypted and encrypted PDF/R files
All indirect references shall have a generation number equal to zero.
All objects referred to be indirect references shall be listed.

NOTE 1 This precludes indirect object references to a non-existent object as described in ISO 32000-1:2008,

7.3.9, “Null Object”.
Stream dictionaries shall not contain a Type key with a value of ObjStm.

NOTE 2 This precludes the use of object streams described in ISO 32000-1:2008, 7.5.7, “Object streams”.

6.3 Catalog dictionary

The Catalog dictionary shall contain the entries required by ISO 32000-1:2008, Table 28. It

shall not contain any optional entries except zero, one or more of the following entries: Version,

ViewerPreferences, PageLayout, PageMode, AcroForm, and Metadata.
6.4 Metadata
6.4.1 General

The Catalog dictionary of a conforming file may contain the Metadata key for which the value is a

metadata stream as defined in ISO 32000-1:2008, 14.3.2.

Page dictionaries may contain the Metadata key for which the value is a metadata stream as defined in

ISO 32000-1:2008, 14.3.2. This metadata stream, if present, shall contain entries with metadata specific

to the page object.
6.4.2 Document level and page level metadata streams

The document level metadata stream and page level metadata streams may use properties defined

[5]

in ISO 16684-1:2019 (XMP) or custom properties. Where custom properties are used, namespaces

shall be used in such a fashion that conflicts are avoided with other entries using the same property

name. Each organization wishing to define and use its own custom properties shall define a suitable

namespace based on a URL that is under the organization’s control.

EXAMPLE 1 Examples for namespaces based on which custom properties can be defined:

— http:// ns .twain .org/ ns/ pdfraster/ v1/ extra _metadata
— http:// ns .twain .org/ ns/ pdfraster/ v1/ some _other _fields

— http:// ns .some _company .com/ ns/ pdf _raster/ version _1/ company _specific _fields

EXAMPLE 2 Properties using the same name that are based on different namespaces:
rdf:about=""
xmlns:org_a="http://ns.org_a.com/pdfraster/1.0/"
xmlns:org_b="http://ns.org_b.com/pdfraster/1.0/"
ABC-123
987-654-321:tre-hgf-bvc

[1]

The TWAIN Working Group provides guidance regarding metadata properties for scanned images .

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ISO 23504-1:2020(E)
6.4.3 Document information dictionary

A document information dictionary may appear within a conforming file. It shall contain no entries

other than Creator, Producer, CreationDate, and ModDate.
6.4.4 XMP Metadata

If an XMP metadata stream is present, each of the entries in the document information dictionary,

shall be represented by the corresponding XMP property value. Table 1 indicates the mapping between

document information dictionary and XMP properties.

Table 1 — Mapping document information dictionary to corresponding XMP properties

Document information dictionary Document level metadata stream
Entry PDF type Property XMP type
Creator text string xmp: CreatorTool AgentName
Producer text string p d f : P r o duc er AgentName
CreationDate date xmp: CreateDate Date
ModDate date xmp: ModifyDate Date
6.5 Page objects
6.5.1 General

Each page image is represented by a PDF page object. The page object is a dictionary that shall be

constructed as mandated by ISO 32000-1:2008.

Each page object shall contain the entries required by ISO 32000-1:2008, Table 30, and shall contain

one Contents entry, and shall not contain any optional entries except zero, one or more of the following

entries: Rotate, Metadata, Annots, and PZ.
6.5.2 Page tree nodes

Page tree nodes shall not contain any entries other than those required by ISO 32000-1:2008, Table 29.

NOTE This provision effectively prohibits the inheritance of such entries. This also applies to the MediaBox

key. Thus, inheritance of the MediaBox key is not possible in a PDF/R file.
6.5.3 Media box

Each page object shall contain a MediaBox entry for which the value shall be of the form [0 0 w h],

where w is the width of the page and h is the height.

NOTE 1 The MediaBox is defined in default user space coordinate units with a default value of 1/72 inch (see

ISO 32000-1:2008, 8.3.2.3, “User space”).

NOTE 2 The MediaBox reflects the size of the page and thus the page image represented on it prior to any

rotation specified by the Rotate entry.

EXAMPLE An ISO A4 sized page would have a MediaBox value of [0 0 595.27559 841.88976].

See Annex A.3, "(informative) Calculating the MediaBox" for a detailed example.
© ISO 2020 – All rights reserved 5
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ISO 23504-1:2020(E)
6.5.4 Annots array and digital signatures

If present, the Annots array in a page object shall only contain widget annotations. Such widget

annotations shall have a value of Sig for the FT entry.

NOTE 1 This provision effectively limits the presence of annotations to widget annotations representing

digital signatures.

For any widget annotation, the width and the height of its Rect entry shall be zero.

NOTE 2 This effectively prohibits the creation of a digital signature that renders a visual presentation on

the page.
6.5.5 Resources dictionary

Each page object shall contain a Resources entry. Each page object's Resources dictionary shall contain

an XObject dictionary, which shall contain one or more image XObject resources that, for the purpose

of this document, are called “strips” (see 6.6, “Strips”). Their order of appearance on the rendered page,

from top to bottom, ignoring rotation in case the Rotate entry is present for the page, shall be reflected

by each strip's name. The first strip on the page shall be named “strip0”. The following strips on the

page, if any, shall be named “strip1”, “strip2”, “strip3”, and so on. The XObject dictionary in a page

object's Resources dictionary shall not contain any other keys.
EXAMPLE Determining the order of strips in an XObject dictionary:
/XObject <<
/strip2 … indirect object reference …
/strip0 … indirect object reference …
/strip1 … indirect object reference …
This is valid, and establishes the order as being strip0, strip1, strip2.
6.5.6 Rotation

Any page object may contain a Rotate entry as defined in ISO 32000-1:2008, Table 30, “Entries in a page

object”. Page tree nodes shall not contain the Rotate key. See A.2, "Scan order versus orientation" for a

possible use case.
NOTE This provision effectively prohibits the inheritance of the Rotate key.
6.5.7 Content stream

Each page object shall contain the Contents key, with a value that is a content stream which draws

the strips of the page image contiguously to fill the MediaBox. Each strip's Width direction shall be

parallel with the width direction of the media box. Each strip's effective width shall be scaled to the

exact width of the media box. Each strip shall be positioned fully inside the media box. The value of the

Contents entry in a page object shall always be a single stream.
NOTE 1 This prohibits the use of an array as the value of a Contents key.

Each content stream shall contain at least one Do operator that references a strip.

NOTE 2 This implies that the page cannot be empty.
A page object’s content stream shall contain only the following operators.
— q;
— Q;
— cm;
6 © ISO 2020 – All rights reserved
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ISO 23504-1:2020(E)
— Do.

NOTE 3 This implies that a content stream only draws the strips for a page image “as is”, e.g. no clipping or

masks are applied, and does not draw anything else. Images can only be present in the form of image XObjects,

not as inline images.

NOTE 4 While the ri operator is prohibited inside content streams, a rendering intent can still be set by means

of an Intent entry in an image XObject.
6.6 Strips
6.6.1 General

Each strip shall be represented by an image XObject as described in ISO 32000-1:2008, 8.9.5, “Image

Dictionaries”. No entries other than Type, Subtype, Length, Filter, DecodeParms, Width, Height,

ColorSpace, BitsPerComponent and Intent shall be present.

The presence of the entries Subtype, Width, Height, Length is always required. The absence of the

ImageMask key and the absence of the JPXDecode filter (as defined in 6.2.2, "Unencrypted PDF/R files",

and 6.2.3, "Encrypted PDF/R files") imply that the presence of the ColorSpace entry is also always

required.

Strips shall be either bitonal, grayscale or RGB images, as defined in 6.6.2, “Bitonal images”, 6.6.3,

“Grayscale images”, and 6.6.4, “RGB images”.

All the strips of a page image shall have the same value for the Width entry and shall all contain the

same entries for ColorSpace and BitsPerComponent. The effective resolution of the strips of a page

image shall be the same in the Width direction between all strips on the page, and shall be the same

in the Height direction between all strips on the page. See Annex A.4, "(informative) Reconstructing

resolution", for calculations how to reconstruct the image resolution.

NOTE 1 This implies that the horizontal resolution of an image XObject, regardless whether it is the only one

on the page or whether it represents one of several strips, can differ from the vertical resolution.

The Intent entry shall either be present or be absent for all strips of a page image. If present, it shall

have the same value for all strips of a
...

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