ISO/IEC 19794-4:2011

INTERNATIONAL ISO/IEC
STANDARD 19794-4
Second edition
2011-12-15
Information technology — Biometric data
interchange formats —
Part 4:
Finger image data
Technologies de l'information — Formats d'échange de données
biométriques —
Partie 4: Données d'image du doigt

Reference number
©
ISO/IEC 2011
©  ISO/IEC 2011
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Published in Switzerland
ii © ISO/IEC 2011 – All rights reserved

Contents Page
Foreword .v
Introduction.vi
1 Scope.1
2 Conformance .1
3 Normative references.2
4 Terms and definitions .2
5 Abbreviated terms .3
6 Data conventions.3
6.1 Byte and bit ordering .3
6.2 Scan sequence .3
7 Image acquisition requirements .3
7.1 General .3
7.2 Pixel aspect ratio .4
7.3 Bit-depth.4
7.4 Grayscale data .4
7.5 Dynamic range.4
7.6 Capture device spatial sampling rate.4
7.7 Image spatial sampling rate .5
7.8 Fingerprint image location .5
7.9 Palm image location.5
8 Finger image record format.5
8.1 Record structure.5
8.2 Finger image general header .6
8.3 Finger/palm image representation header.9
8.4 Extended data .18
9 Registered format type identifiers .23
Annex A (normative) Conformance test methodology .24
Annex B (normative) Capture device certifications .25
Annex C (informative) Finger image data record example .49
Annex D (informative) Conditions for capturing finger image data.51
Annex E (normative) WSQ Gray-scale fingerprint image compression specification.60
Bibliography.91

Figures
Figure 1 — Order of scanned lines .4
Figure 2 — Finger image record structure .6
Figure 3 — Order and size of fields in the finger image record.7
Figure 4 — Image quality layout.13
Figure 5 — Finger orientation for segmentation.22
© ISO/IEC 2011 – All rights reserved iii

Tables
Table 1 — General record header. 8
Table 2 — Finger image representation header record. 9
Table 3 — Image and extended data . 11
Table 4 — Capture device technology. 12
Table 5 — Identifiers for certification schemes specified in the annexes. 14
Table 6 — Finger position codes . 15
Table 7 — Multiple finger position codes. 15
Table 8 — Palm codes. 16
Table 9 — Compression algorithm codes. 17
Table 10 — Finger and palm impression codes . 18
Table 11 — Extended data area type codes . 19
Table 12 — Segmentation data . 20
Table 13 — Annotation data . 22
Table 14 — Format Type Identifiers . 23

iv © ISO/IEC 2011 – All rights reserved

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. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75% of the national bodies casting a vote.
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.
ISO/IEC 19794-4 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
This second edition cancels and replaces the first edition (ISO/IEC 19794-4:2005). It reflects the
harmonization across the second generation of ISO/IEC 19794. Clause 8 has been technically revised and
contains descriptions of the harmonized general and representation headers. Annex A is under development
and will contain an amendment for conformance testing methodology for this part of ISO/IEC 19794. Annex B
contains capture device certifications for capturing finger image data. Annex B has been technically revised.
Annex D describes conditions for capturing finger image data, and Annex E contains the WSQ Gray-scale
fingerprint image compression specification. The former Annex A “Image Quality Specification” has been
removed.
ISO/IEC 19794 consists of the following parts, under the general title Information technology — Biometric data
interchange formats:
⎯ Part 1: Framework
⎯ Part 2: Finger minutiae data
⎯ Part 3: Finger pattern spectral data
⎯ Part 4: Finger image data
⎯ Part 5: Face image data
⎯ Part 6: Iris image data
⎯ Part 7: Signature/sign time series data
⎯ Part 8: Finger pattern skeletal data
⎯ Part 9: Vascular image data
⎯ Part 10: Hand geometry silhouette data
⎯ Part 11: Signature/sign processed dynamic data
⎯ Part 13: Voice data
⎯ Part 14: DNA data
© ISO/IEC 2011 – All rights reserved v

Introduction
In the forensic community, the capture and transmission of fingerprint images has been a common choice for
the exchange of fingerprint information used by Automatic Fingerprint Identification Systems (AFIS) for the
identification of individuals. However, little to no fingerprint information is being exchanged between
equipment from different vendors in the biometric user verification and access community. This has been due
in part to the lack of agreement between vendors on the amount and type of information to capture, the
method of capture, and the information to be exchanged.
ISO/IEC 19794 is a series of International Standards being developed by ISO/IEC JTC 1/SC 37 that supports
interoperability and data interchange among biometric applications and systems. The series specifies
requirements that solve the complexities of applying biometrics to a wide variety of personal recognition
applications, whether such applications operate in an open systems environment or consist of a single, closed
system. Additional information regarding the series is provided in ISO/IEC 19794-1.
This part of ISO/IEC 19794 is intended for those applications requiring the exchange of raw or processed
fingerprint and palm images that may not necessarily be limited by the amount of resources required for data
storage or transmitting time. It can be used for the exchange of scanned fingerprints containing detailed image
pixel information. This part of ISO/IEC 19794 can also be used to exchange processed fingerprint image data
containing considerably fewer pixels per inch and/or a lesser number of grayscale levels. This is in contrast to
other parts of ISO/IEC 19794 used for exchanging lists of fingerprint characteristics such as minutiae, patterns,
or other variants. These formats require considerably less storage than a fingerprint image. However, by using
any of the other parts of ISO/IEC 19794, information recorded in one standard format cannot be used by
algorithms designed to operate with another type of information. In other words, minutiae data records cannot
be compared with pattern skeletal data comparison subsystems.
Although the minutiae, pattern, or other approaches produce different intermediate outputs, all shall initially
capture a reasonably high quality fingerprint image before reducing the size of the image (in bytes) or
developing a list of characteristic data from the image. Use of the captured or processed image can provide
interoperability among vendors relying on minutiae-based, pattern-based or other algorithms. As a result, 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 fingerpr
...