ISO/IEC 19794-4:2005

INTERNATIONAL ISO/IEC
STANDARD 19794-4
First edition
2005-06-01
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 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO/IEC 2005
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 either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO/IEC 2005 – All rights reserved

Contents Page
Foreword.v
Introductio n.vi
1 Scope.1
2 Conformance.1
3 Normative references .1
4 Terms and definitions.1
5 Abbreviated terms .3
6 Data conventions .3
6.1 Byte and bit ordering.3
6.2 Scan sequence.3
7 Image acquisition requirements .4
7.1 General .4
7.2 Pixel aspect ratio .4
7.3 Pixel depth.5
7.4 Grayscale data .5
7.5 Dynamic range .5
7.6 Scan resolution.6
7.7 Image resolution .6
7.8 Fingerprint image location .6
8 Finger image record format.6
8.1 Record structure .6
8.2 General record header.7
8.2.1 Required fields.7
8.2.2 Format identifier.7
8.2.3 Version number.8
8.2.4 Record length.8
8.2.5 Capture device ID.8
8.2.6 Image acquisition level.8
8.2.7 Number of finger/palm images.8
8.2.8 Scale units.8
8.2.9 Scan resolution (horizontal).8
8.2.10 Scan resolution (vertical) .8
8.2.11 Image resolution (horizontal).8
8.2.12 Image resolution (vertical) .9
8.2.13 Pixel depth.9
8.2.14 Image compression algorithm .9
8.2.15 Reserved.9
8.3 Finger record header .10
8.3.1 Required fields.10
8.3.2 Length of finger/palm data block.10
8.3.3 Finger/palm position.10
8.3.4 Count of views .11
8.3.5 View number.12
8.3.6 Finger/palm image quality.12
8.3.7 Impression type .12
8.3.8 Horizontal line length.12
8.3.9 Vertical line length .12
8.3.10 Finger/palm image data .12
© ISO/IEC 2005 — All rights reserved iii

Annex A (normative) Image quality specifications .13
A.1 Scope and purpose.13
A.2 Fingerprint scanners .13
A.2.1 Geometric image accuracy.13
A.2.2 Modulation transfer function.14
A.2.3 Signal-to-noise ratio .14
A.2.4 Grayscale range of image data .15
A.2.5 Grayscale linearity .16
A.2.6 Output gray level uniformity .16
A.3 Latent print scanners.16
A.3.1 Geometric image accuracy.17
A.3.2 Modulation transfer function.17
Annex B (informative) Finger image data record example .19
Bibliography.21
iv © ISO/IEC 2005 — 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.
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
The following parts are under preparation:
 Part 7: Signature/sign behavioral data
 Part 8: Finger pattern skeletal data

© ISO/IEC 2005 – 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.
This part of the ISO/IEC 19794 standard is intended for those applications requiring the exchange of raw or
processed fingerprint 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 greyscale 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.
How
...