ISO/IEC 39794-4:2019

Information technology — Extensible biometric data interchange formats — Part 4: Finger image data

This document specifies: — generic extensible data interchange formats for the representation of friction ridge image data: a tagged binary data format based on an extensible specification in ASN.1 and a textual data format based on an XML schema definition that are both capable of holding the same information; — examples of data record contents; — application specific requirements, recommendations, and best practices in data acquisition; and — conformance test assertions and conformance test procedures applicable to this document.

Titre manque — Partie 4: Titre manque

General Information

• Status: Published
• Publication Date: 19-Dec-2019
• ICS: 35.240.15 - Identification cards. Chip cards. Biometrics
• Technical Committee: ISO/IEC JTC 1/SC 37 - Biometrics
• Drafting Committee: ISO/IEC JTC 1/SC 37/WG 3 - Biometric data interchange formats
• Current Stage: 6060 - International Standard published
• Start Date: 20-Dec-2019
• Due Date: 09-Dec-2019
• Completion Date: 20-Dec-2019

Relations

• Amended By: ISO/IEC 39794-4:2019/Amd 1:2023 - Information technology — Extensible biometric data interchange formats — Part 4: Finger image data — Amendment 1: Extension towards improved interoperability with ANSI/NIST-ITL
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 39794-4
First edition
2019-12
Information technology — Extensible
biometric data interchange formats —
Part 4:
Finger image data
Reference number
ISO/IEC 39794-4:2019(E)
©
ISO/IEC 2019

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ISO/IEC 39794-4:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ISO/IEC 39794-4:2019(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 5
5 Conformance . 6
6 Modality specific information . 6
6.1 Capture recommendations . 6
6.1.1 Fingerprint image . 6
6.1.2 Palm image . 6
6.2 Image coordinate system considerations . 7
6.3 Image representation requirements . 7
6.3.1 General. 7
6.3.2 Colorspace . 7
6.3.3 Pixel aspect ratio . 7
6.3.4 Bit-depth . 8
6.3.5 Image spatial sampling rate . 8
7 Abstract data elements . 8
7.1 Purpose and overall structure . 8
7.2 Finger image data block . 9
7.3 Version block . 9
7.4 Representation blocks .10
7.5 Position .10
7.6 Impression .10
7.7 Image data format .11
7.7.1 Supported data format .11
7.7.2 PGM encoding definition .11
7.8 Image data .12
7.9 Capture date/time block . .12
7.10 Capture device block .12
7.10.1 Model identifier block .12
7.10.2 Capture device technology identifier .12
7.10.3 Certification identifier blocks .13
7.11 Quality blocks .14
7.12 Spatial sampling rate block .14
7.13 Position computed by capture device .14
7.14 Original rotation .14
7.15 Image rotated to vertical .14
7.16 Image has been lossily compressed .14
7.17 Segmentation blocks .15
7.18 Annotation blocks .15
7.19 PAD data block.15
7.20 Comment blocks .16
7.21 Vendor specific data blocks .16
8 Encoding .16
8.1 Tagged binary encoding .16
8.2 XML encoding .16
9 Registered BDB format identifiers .16
Annex A (normative) Formal specifications .17
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ISO/IEC 39794-4:2019(E)

Annex B (informative) Encoding examples .29
Annex C (normative) Conformance testing methodology .33
Annex D (normative) Capture device certifications .38
Annex E (informative) Conditions for capturing fingerprint image data .62
Annex F (normative) WSQ greyscale finger image compression specification .71
Bibliography .97
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ISO/IEC 39794-4:2019(E)

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that
are members of ISO or IEC participate in the development of International Standards through
technical committees established by the respective organization to deal with particular fields of
technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also
take part in the work.
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 document 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 and IEC 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) or the IEC
list of patent declarations received (see http:// patents .iec .ch).
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 Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
A list of all parts in the ISO/IEC 39794 series can be found on the ISO website.
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.
The purchase of this ISO/IEC document carries a copyright licence for the purchaser to use ISO/IEC
copyright in the schemas in the annexes to this document for the purpose of developing, implementing,
installing and using software based on those schemas, subject to ISO/IEC licensing conditions set out in
the schemas.
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ISO/IEC 39794-4:2019(E)

Introduction
Biometric data interchange formats enable the interoperability of different biometric systems. The first
generation of biometric data interchange formats has been published between 2005 and 2007 in the
first edition of the ISO/IEC 19794 series. From 2011 onwards, the second generation of biometric data
interchange formats was published in the second edition of the established parts and the first edition
of some new parts of the ISO/IEC 19794 series. In the second generation of biometric data interchange
formats, new useful data elements such as data elements related to biometric sample quality have been
added, the header data structures were harmonized across all parts of the ISO/IEC 19794 series, and
XML encoding has been added in addition to the binary encoding.
In anticipation of the future need for additional data elements and to avoid future compatibility issues,
ISO/IEC JTC 1/SC 37 has developed the ISO/IEC 39794 series as a third generation of biometric data
interchange formats, defining extensible biometric data interchange formats capable of including
future extensions in a defined way. Extensible specifications in ASN.1 (Abstract Syntax Notation One)
and the distinguished encoding rules of ASN.1 form the basis for encoding biometric data in binary
tag-length-value formats. XML schema definitions form the basis for encoding biometric data in XML
(eXtensible Markup Language).
This third generation of finger image data interchange formats complements ISO/IEC 19794-4 (both
the 2005 and 2011 editions). The first generation of biometric data interchange formats, which has been
adopted, e.g. by ICAO for the biometric data stored in machine readable travel documents, is expected
to be retained in the standards catalogue as long as needed.
This document is intended for those applications requiring the exchange of raw or processed fingerprint
and other friction ridge images (for example, palm images) that may not necessarily be limited in the
amount of resources available for data storage or transmitting time. It can be used for the exchange of
scanned fingerprints containing detailed image pixel information.
Use of the captured or processed image allows interoperability among biometric systems relying on
minutiae-based, pattern-based or other algorithms. Thus, data from the captured finger image offers the
developer more freedom in choosing or combining comparison algorithms. For example, an enrolment
image may be stored on a contactless chip located on an identification document. This will allow future
verification of the holder of the document with systems that rely on either minutiae-based or pattern-
based algorithms. Establishment of an image-based representation of fingerprint information will not
rely on pre-established definitions of minutiae, patterns or other types. It will provide implementers
with the flexibility to accommodate images captured from dissimilar devices, varying image sizes,
spatial sampling rates and different greyscale depths. Use of the finger image will allow each vendor to
implement their own algorithms to determine whether two fingerprint records are from the same finger.
This document supports both binary and XML encoding, to support a spectrum of user requirements.
With XML, this document meets the requirements of modern IT architectures. With binary encoding
this document is also able to be used in bandwidth or storage constrained environments.
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INTERNATIONAL STANDARD ISO/IEC 39794-4:2019(E)
Information technology — Extensible biometric data
interchange formats —
Part 4:
Finger image data
1 Scope
This document specifies:
— generic extensible data interchange formats for the representation of friction ridge image data: a
tagged binary data format based on an extensible specification in ASN.1 and a textual data format
based on an XML schema definition that are both capable of holding the same information;
— examples of data record contents;
— application specific requirements, recommendations, and best practices in data acquisition; and
— conformance test assertions and conformance test procedures applicable to this document.
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/IEC 2382-37, Information technology — Vocabulary — Part 37: Biometrics
ISO/IEC 8824-1, Information technology — Abstract Syntax Notation One (ASN.1): Specification of basic
notation — Part 1
ISO/IEC 8825-1, Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER), and Distinguished Encoding Rules (DER)
ISO/IEC 14495-1, Information technology — Lossless and near-lossless compression of continuous-tone still
images: Baseline
ISO/IEC 15444 (all parts), Information technology — JPEG 2000 image coding system
ISO/IEC 15948, Information technology — Computer graphics and image processing — Portable Network
Graphics (PNG): Functional specification
ISO/IEC 39794-1, Information technology — Extensible biometric data interchange formats — Part 1:
Framework
W3C Recommendation, XML Schema Part 1: Structures (Second Edition), 28 October 2004
W3C Recommendation, XML Schema Part 2: Datatypes (Second Edition), 28 October 2004
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 2382-37, ISO/IEC 39794-1
and the following apply.
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ISO and IEC maintain terminological databases for use in standardisation at the following addresses:
— IEC Electropedia available at http:// www .electropedia .org/
— ISO Online Browsing Platform available at http:// www .iso .org/ obp.
3.1
spatial sampling rate
number of pixels per unit distance used by a sensor or scanning device to initially capture an image
3.2
coding model
procedure used to convert input data into symbols to be coded
3.3
coding process
general term for referring to an encoding process, a decoding process, or both
3.4
column
samples per line in an image
3.5
compressed data
either compressed image data or table specification data or both
3.6
compressed image data
coded representation of an image
Note 1 to entry: As specified in Annex F.
3.7
compression
reduction in the number of bits used to represent source image data
3.8
decoder
embodiment of a decoding process
3.9
decoding process
process which takes as its input compressed image data and outputs a continuous-tone image
3.10
dequantization
inverse procedure to quantization by which the decoder recovers a representation of the DWT
coefficients
3.11
reconstructed image
continuous-tone image which is the output of the decoder
Note 1 to entry: As defined in Annex F.
3.12
source image
continuous-tone image used as input to any encoder
Note 1 to entry: As defined in Annex F.
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3.13
digital image
two-dimensional array of data
3.14
downsampling
procedure by which the spatial resolution of an image is reduced
3.15
DWT
discrete wavelet transform
linear transformation, implemented by a multirate filter bank, that maps a digital input signal to a
collection of output subbands
3.16
encoder
embodiment of an encoding process
3.17
encoding process
process which takes as its input a continuous-tone image and outputs compressed image data
3.18
entropy-coded data segment
independently decodable sequence of entropy encoded bytes of compressed image data
3.19
entropy decoder
embodiment of an entropy decoding procedure
3.20
entropy decoding
lossless procedure which recovers the sequence of symbols from the sequence of bits produced by the
entropy coder
3.21
entropy encoder
embodiment of an entropy encoding procedure
3.22
entropy encoding
lossless procedure which converts a sequence of input symbols into a sequence of bits such that the
average number of bits per symbol approaches the entropy of the input symbols
3.23
fingerprint image
representation of an area of friction skin on the fleshy surface of a finger located horizontally between
the two edges of the fingernail and vertically between the first joint and the tip of a finger
Note 1 to entry: It contains a unique pattern of friction ridge and valley information commonly referred to as a
“fingerprint”.
3.24
Huffman decoder
embodiment of a Huffman decoding procedure
3.25
Huffman decoding
entropy decoding procedure which recovers the symbol from each variable length code produced by
the Huffman encoder
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3.26
Huffman encoder
embodiment of a Huffman encoding procedure
3.27
Huffman encoding
entropy encoding procedure which assigns a variable length code to each input symbol
3.28
Huffman table
set of variable length codes required in a Huffman encoder and Huffman decoder
3.29
image data
either source image data or reconstructed image data
3.30
image spatial sampling rate
number of pixels per unit distance in the image
Note 1 to entry: This may be the result of processing a captured image. The original captured scanned image may
have been subsampled, scaled, downsampled, or otherwise processed.
3.31
interchange format
representation of compressed image data for exchange between application environments
3.32
lossless
descriptive term for encoding and decoding processes and procedures in which the output of the
decoding procedure(s) is identical to the input to the encoding procedure(s)
3.33
marker
two-byte code in which the first byte is FF and the second byte is a value between 1 and FE
Hex Hex
3.34
marker segment
marker and associated set of parameters
3.35
palm
friction ridge skin on the side and underside of the hand
3.36
parameter
fixed length integers 8, 16, or 32 bits in length, used in the compressed data format
3.37
plain fingerprint image
image captured from a finger placed on a platen without any rolling movement
3.38
procedure
set of steps which accomplishes one of the tasks which comprise an encoding or decoding process
3.39
progressive
separation of data segments into blocks that can be transmitted successively to allow the
compressed image data to be decoded at successively higher levels of resolution
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3.40
quantization table
set of quantization values (i.e., bin widths) used to quantize DWT coefficients within the subbands
3.41
quantize
act of performing the quantization procedure for a DWT coefficient
3.42
restart interval
number of coefficients processed as an independent sequence within an image
3.43
restart marker
marker that separates two restart intervals in an image
3.44
rolled fingerprint image
image captured that is located between the two edges of the fingernail
Note 1 to entry: This type of image is typically acquired using a rolling motion from one edge of the fingernail to
the other.
3.45
run length
number of consecutive symbols of the same value
3.46
SWT
symmetric wavelet transform
linear transform implemented by applying a DWT to a periodized symmetric extension of the input signal
3.47
sample
one element in the two-dimensional array which comprises a finger image
3.48
table specification data
coded representation from which the tables, used in the encoder and decoder, are generated
3.49
upsampling
procedure by which the spatial resolution of an image is increased
4 Abbreviated terms
For the purposes of this document, the abbreviated terms given in ISO/IEC 39794-1 and the
following apply.
ppcm pixels per centimetre
ppi pixels per inch
CTF contrast transfer function
JPEG joint photographic experts group
MTF modulation transfer function
PGM portable gray map
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PNG portable network graphics
TIR total internal reflection
WSQ wavelet scalar quantization
5 Conformance
A biometric data block (BDB) conforms to this document if it satisfies all of the requirements related to:
— its data structure, data values and the relationships between its data elements as specified
throughout Clauses 6, 7, 8, and Annex A, and
— the relationship between its data values and the input biometric data from which the biometric data
record was generated as specified throughout Clauses 6, 7, 8, and Annex A.
A system that produces biometric data records conforms to this document if all biometric data
records that it outputs conform to this document (as defined above) as claimed in the implementation
conformance statement (ICS) associated with that system. A system does not need to be capable of
producing biometric data records that cover all possible aspects of this document, but only those that
are claimed to be supported by the system in the ICS.
A system that uses biometric data records conforms to this document if it can read, and use for the
purpose intended by that system, all biometric data records that conform to this document (as defined
above) as claimed in the ICS associated with that system. A system does not need to be capable of using
biometric data records that cover all possible aspects of this document, but only those that are claimed
to be supported by the system in an ICS.
6 Modality specific information
6.1 Capture recommendations
6.1.1 Fingerprint image
This document is designed to accommodate both plain (flat) or rolled fingerprint images. Biometric
systems perform better if the volar pad of the finger is centred both horizontally and vertically in the
image capture area. Therefore, when capturing a fingerprint image, the centre of the fingerprint image
should be located in the approximate centre of the image capture area.
For multiple finger verification and/or identification purposes, there exist fingerprint capture devices
that will acquire images of multiple fingers during a single capture cycle. These devices are capable of
capturing the plain impressions from two, three or four adjacent fingers of either hand during a single
scanning. The plain impressions from the two thumbs or two index fingers can also be captured at one
time. Therefore, with three placements of the fingers on a device’s scanning surface all ten fingers from
an individual would be acquired in three scans – right four fingers, left four fingers, and two thumbs.
For these multi-finger captures, half of the captured fingers should be located to the left of the
...