ISO/IEC JTC 1/SC 37 N470 2004-03-01
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Replaces:
ISO/IEC JTC 1/SC 37
Biometrics
Document Type: Text for CD ballot or comment
Document Title: Text of ISO/IEC CD 19794-3, Biometric Data Interchange Formats —
Part 3: Finger Pattern Spectral Data
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© ISO/IEC -2004 – All rights reserved
Reference number of working document: ISO/IEC JTC 1/SC 37 N
Date: 2004-03-01
Reference number of document: ISO/IEC CD 19794-3
Committee identification: ISO/IEC JTC 1/SC 37
Secretariat: ANSI
Biometric Data Interchange Formats —
Part 3: Finger Pattern Spectral Data
Élément introductif — Élément principal — Partie n: Titre de la partie
Warning
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to
change without notice and may not be referred to as an International Standard.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Document type: International standard
Document subtype: if applicable
Document stage:
Document language: E
ISO/IEC CD 19794-3
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ISO/IEC CD 19794-3
Table of Contents
1 Scope ............................................................................................................................7
2 Conformance................................................................................................................7
3 Normative references ...................................................................................................7
4 Terms and definitions...................................................................................................7
4.1 Biometric measure............................................................................................... 7
4.2 Biometric Matching Algorithm............................................................................ 7
4.3 Biometric Data..................................................................................................... 8
4.4 Biometric Sample................................................................................................. 8
4.5 Biometric System................................................................................................. 8
4.6 Bit-Depth............................................................................................................. 8
4.7 Capture................................................................................................................ 8
4.8 Cell...................................................................................................................... 8
4.9 Cell Structure ...................................................................................................... 8
4.10 Cell Quality Group.............................................................................................. 8
4.11 Comparison......................................................................................................... 8
4.12 Crop .................................................................................................................... 9
4.13 Dimension............................................................................................................ 9
4.14 Down-sample....................................................................................................... 9
4.15 Encryption........................................................................................................... 9
4.16 Enrollment........................................................................................................... 9
4.17 Reduced resolution finger image.......................................................................... 9
4.18 Finger Pattern Spectral Data Interchange Data................................................... 9
4.19 Minimal Spatial Wavelength................................................................................ 9
4.20 Packed Data Format............................................................................................ 9
4.21 Pad..................................................................................................................... 10
4.22 Raw Fingerprint Image...................................................................................... 10
4.23 Reference Template ........................................................................................... 10
4.24 Resolution.......................................................................................................... 10
4.25 Template Size..................................................................................................... 10
5 Finger Pattern Spectral Interchange Data ..................................................................10
5.1 Overview............................................................................................................ 10
5.2 Step 1) Reduction in resolution.......................................................................... 10
ISO/IEC CD 19794-3
5.3 Step 2) Cellular Representation......................................................................... 11
5.3.1 Cell Structure .......................................................................................................................................12
5.4 Quality............................................................................................................... 14
6 Finger Pattern Spectral Data Record..........................................................................15
6.1 Introduction....................................................................................................... 15
6.2 Record Header................................................................................................... 16
6.2.1 Format Identifier..................................................................................................................................16
6.2.2 Version Number ..................................................................................................................................16
6.2.3 Length of Record .................................................................................................................................16
6.2.4 Capture Device ID..............................................................................................................................17
6.2.5 Number of Finger Patterns in Record..............................................................................................17
6.2.6 Resolution of Finger Pattern in x-direction....................................................................................17
6.2.7 Resolution of Finger Pattern in y-direction....................................................................................17
6.2.8 Number of Cells in x-direction.........................................................................................................17
6.2.9 Number of Cells in y-direction.........................................................................................................17
6.2.10 Number of Pixels in Cells in x-direction...................................................................................17
6.2.11 Number of Pixels in Cells in y-direction...................................................................................17
6.2.12 Cellular x-offset .............................................................................................................................17
6.2.13 Cellular y-offset .............................................................................................................................17
6.2.14 Number of Pixels between Cell Centers in x-direction ...........................................................18
6.2.15 Number of Pixels between Cell Centers in y-direction ...........................................................18
6.2.16 Number of Components Extracted from each cell...................................................................18
6.2.17 Type of window.............................................................................................................................18
6.2.18 Wavelength and angle generating mechanism for each filter ................................................18
6.2.19 Method for selecting retained components................................................................................18
6.2.20 Naming and ordering of retained components..........................................................................18
6.2.21 Bit-depth of Cell Structure Angle ...............................................................................................18
6.2.22 Bit-depth of Cell Structure Wavelength.....................................................................................19
6.2.23 Bit-depth of Cell Structure Phase Offset ...................................................................................19
6.2.24 Bit-depth of Cell Structure Quality.............................................................................................19
6.2.25 Cell Quality Granularity ...............................................................................................................19
6.2.26 Reserved Bytes...............................................................................................................................19
6.3 Single Finger Pattern Spectral Record Format.................................................. 19
6.3.1 Finger Pattern Record Header...........................................................................................................19
6.3.2 Finger Pattern Spectral Data .............................................................................................................21
6.3.3 Extended Data......................................................................................................................................21
7 Annex A (informative) - Finger Pattern Spectral Data Record Example 1...............29
8 Annex B (informative) - Finger Pattern Spectral Data Record Example 2...............34
9 Annex C (informative) - Finger Pattern Spectral Data Record Example 3...............37
ISO/IEC CD 19794-3
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 the
member bodies for voting. Publication as an International Standard requires approval by
at least 75 % of the member 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/IEC19794-3 was prepared by Joint Technical Committee ISO/IEC JTC 1, Subcommittee
SC 37, Biometrics.
ISO/IEC19794 consists of the following parts, under the general title 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 Data
 Part 8: Finger Pattern Skeletal Data
ISO/IEC CD 19794-3
FINGER PATTERN SPECTRAL DATA FORMAT
Introduction
In the interest of implementing interoperable personal biometric recognition systems, this
ISO/IEC Standard establishes a data interchange format for fingerprint spectral data
exchange. Goal of the standard: to allow the exchange of local or global spectral data
derived from a fingerprint image without the exchange of the entire image. This will
allow more compact data representations. Further, we wish the standard to be useful to
many aspects of the fingerprint recognition process, possibly including flow field
extraction, level 1 characterization, “core” location, quality assessment, comparison
methods, and (possibly) “privacy” assurance.
This standard would allow for representation of both Discrete Fourier Transform and
(single-scale) Gabor Filter components extracted from global or stationary (not image
dependent and not varying over the image) local overlapping or non-overlapping
uniform-sized regions of the original intensity (non-color) image. Some or all of the
extracted spectral components will be stored in the data format, depending upon the
implementation.
Previous versions of this proposed standard will be seen as a particular example of this
standard using non-overlapping local areas and retaining the phase, wavelength and offset
of the highest energy spectral components from each local “cell”. This standard does not
accommodate multi-scale (wavelet) decompositions.
There are fingerprint recognition algorithms that use spectral data directly for pattern
matching. Spectral data-based recognition algorithms process “globally" sections (cells)
of biometric images, in contrast to morphological-based algorithms, which extract
singularities in the morphological features. At the current time, there is no established
mechanism for the interchange of finger pattern spectral information for use with
spectral-based fingerprint matching algorithms.
By establishing a standard for spectral-based representation of fingerprints, we:
•Allow interoperability among fingerprint recognition vendors based on a small data
record.
•Support the proliferation of low-cost commercial fingerprint sensors with limited
coverage, dynamic range, or resolution.
•Define a data record format that can be used with portable devices and media, such as
smart cards.
•Encourage the adoption of biometrics in applications where interoperability is required.
Note that it is recommended that biometric data protectiontechniques in ANSI/X9 X9.84
or ISO/IEC 15408:1999 are used to safeguard the biometric data defined herein for
confidentiality, integrity and availability.
ISO/IEC CD 19794-3
1 Scope
This standard specifies the interchange format for the exchange of spectral-based
fingerprint characterization data.
2 Conformance
A biometric system or algorithm conforms to this standard if it satisfies the mandatory
requirements for the generation of the finger pattern spectral cell information as defined
in section 5 and the generation of the data record as described in section 6.
3 Normative references
The following referenced documents are indispensable for the application 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.
ANSI/INCITS 358-2002 - Information technology - BioAPI Specification
ANSI/NIST-ITL 1-2000, Standard Data Format for the Interchange of Fingerprint, Facial,
& Scar mark & Tattoo (SMT) Information
ISO/IEC CD3 19785-1.3 - Common Biometric Exchange Formats Framework (CBEFF)
ISO/IEC 15408:1999 - Evaluation criteria for IT security
4 Terms and definitions
For the purposes of this -International Standard, the following terms and definitions apply.
4.1 Biometric measure
A measurable, physical characteristic or personal behavioural trait used to recognize
individuals.
4.2 Biometric Matching Algorithm
A sequence of instructions used by a biometric system to process biometric information.
A biometric matching algorithm is used by the biometric system to compute whether a
biometric sample and a reference template/model originate from the same source (the
same human body).
ISO/IEC CD 19794-3
4.3 Biometric Data
Information extracted from a biometric sample and used either to build a reference
template (template data), reference model, or to compare against a previously created
reference template (comparison data) or model.
4.4 Biometric Sample
Raw data representing a biometric characteristic of an end-user as captured by a
biometric system (for example, the image of a fingerprint).
4.5 Biometric System
An automated system capable of:
capturing a biometric sample from an end user;
extracting biometric data from that sample;
comparing the biometric data with that contained in one or more reference templates or
models;
deciding how well they match; and
indicating whether or not a recognition has been made.
4.6 Bit-Depth
The number of bits used to represent a data record parameter.
4.7 Capture
The method of taking a biometric sample from the end user.
4.8 Cell
Overlapping or non-overlapping regions of a fingerprint image (see 4.17) of single size
across the entire image. Multi-scale cells are not accommodated in this standard.
4.9 Cell Structure
Structure used to represent the information contents of cell.
4.10 Cell Quality Group
The Group of Cells to which the Finger Quality parameter refers.
4.11 Comparison
The process of measuring the similarity or difference between a biometric sample and a
previously stored reference template or pattern generated by a model.
ISO/IEC CD 19794-3
4.12 Crop
Remove the outer regions of an image to reduce the size.
4.13 Dimension
Number of pixels in an acquired biometric sample image either x- or y-direction.
4.14 Down-sample
Reduce the resolution of an image by re-sampling the image with a reduced number of
pixels. Proper filtering is implied to prevent aliasing.
4.15 Encryption
The act of converting plain text into cipher-text through a reversible mathematical
process.
4.16 Enrollment
The process of collecting biometric samples from an individual and the subsequent
preparation and storage of biometric reference templates or models.
4.17 Reduced resolution finger image
Sub-portion and/or down-sampled version of a raw fingerprint image (see 4.22).
4.18 Finger Pattern Spectral Data Interchange Data
Spectral data derived from the Finger Pattern.
4.19 Minimal Spatial Wavelength
The minimal spatial wavelength is the (spatial) wavelength (measured in pixels) at which
exactly two samples of an image span a complete period of a (co)sinusoidal pattern. This
is therefore the maximal spatial frequency that can be supported by a sampling resolution,
and is known as the Nyquist frequency. The minimal spatial wavelength is the inverse of
the Nyquist frequency.
4.20 Packed Data Format
Data are stored in a compacted bit form with no record separators or field tags - fields are
separated by bit count only.
ISO/IEC CD 19794-3
4.21 Pad
Embed an image in a larger array (usually filled with zeroes) to produce a resulting image
of greater dimension.
4.22 Raw Fingerprint Image
Biometric sample as captured by a fingerprint sensor. This raw image will usually retain
the full resolution and spatial extent permitted by the sensor.
4.23 Reference Template
Processed Biometric Data stored as representative of the user’s biometric sample.
4.24 Resolution
The number of picture elements (pixels) per unit length in a sampled fingerprint image.
Pixels per cm (ppcm) will be used in this standard as the units of resolution. Note that 1
pixel per cm (ppcm) = 2.54 pixels per inch (ppi).
4.25 Template Size
The amount of computer (or storage medium) memory taken up by the biometric
reference template.
5 Finger Pattern Spectral Interchange Data
5.1 Overview
This ISO/IEC standard for finger pattern spectral interchange data is based on:
1) conversion of the raw fingerprint image to a cropped and down-sampled finger pattern,
followed by;
2) cellular representation of the finger pattern image to create the finger pattern spectral
interchange data.
5.2 Step 1) Reduction in resolution
Spectral pattern-based fingerprint processing may require less image resolution than is
traditionally provided by sensors. Therefore, the first step in data reduction typically
involves a re-sampling of the data to a lower resolution.
ISO/IEC CD 19794-3
5.3 Step 2) Cellular Representation
Finger
Pattern
Sample
Cell
Figure 1. Diagram to illustrate Cellular Representation of Finger Pattern.
Cellular representation of the finger pattern data comprises dividing the central, or other,
portion of the finger pattern into a grid of overlapping or non-overlapping cells. At each
cell, the finger pattern will be represented by one of a number of different cell structures,
as described below.
ISO/IEC CD 19794-3
5.3.1 Cell Structure
Each of the cells can be decomposed into a two-dimensional spectral representation. In
the case of square cells of side N, a two-dimensional Discrete Fourier Transform (DFT)
will result in N/2 complex spectral components in one dimension and N complex
components in the other. Each component will be characterized by a wavelength in the x
and y directions (which combined indicate propagation direction), an amplitude, and a
phase. For each spectral component, the spatial frequency,f, is given by SQRT(f2
x + f2
y).
The wavelength, λ, is given by the inverse of the spatial frequency. The propagation
angle, θ, for each component is given by ARCTAN (fy, fx).
In the case of the cell dimension being the same as that of the entire image, the DFT
spectral representation becomes a globa l decomposition. An NxM image will have N/2
by M/2 discrete frequencies in spectral decomposition. If all N*M/4 frequency
magnitude/phase or complex components are stored, the image can be exactly
reconstructed by these N*M/2 components. Storage and reconstruction from fewer
components will result in information loss, meaning that the exact image will not be
reconstructable from the reduced number of components. Depending upon the number
and selection method, minutiae patterns may be reconstructable fromsome reduced sets
of components.
A two-dimensional spectral decomposition of an entire image using a 2-d Discrete
Fourier Transform (DFT) should show most of the spectral energy within an annulus of
the frequency plane. For most people, this annulus will be at about the 14 -18 pixel
wavelength when the original sampling is at 500dpi. Of course other image resolutions
will have different spatial wavelengths.
In the case of cell dimensions on the order of a ridge wavelength, the DFT spectral
decomposition of the finger pattern may be dominated by a single component of high
amplitude and a spatial wavelength on the order of the finger pattern ridge wavelength.
Such a case is shown in Figure 2.
ISO/IEC CD 19794-3
Sample
Cell
θ
λ
δ
(0,0) x
y
Figure 2. Cellular Representation of Finger Pattern.
The range of each of these parameters is given below:
θ: 0 to 180 degrees
• Note that 0 degrees is defined as parallel to the x, or horizontal, axis, and θ
increases in a counter-clockwise rotation.
λ, minimal spatial wavelength to ∞ (but limited in practice to twice the number of pixels
across the longest diagonal in the image)
f: 0 to Maximal Spatial Frequency
δ: 0 to 360 degrees
• Note that δ is defined between the origin of the cell (at the bottom-left
corner) and the location of the first crest of the co-sinusoidal function in a
positive direction in either x or y (or both) directions.
ISO/IEC CD 19794-3
Figure 3 below demonstrates an example of the primary spectral component of a finger
pattern cell of size on the order of a ridge wavelength. Both of the images in this figure
were enhanced for illustrative purposes.
a) b)
Figure 3. a) Example of the local finger pattern information in a cell, and b) the resulting cell
structure chosen for representation.
In this manner, each of the finger pattern cells is represented by one of the possible
permutations of cell structure. In the case of cells of size on the order of a ridge
wavelength, the resulting data will comprise the majority of the public portion of the
Finger Pattern Spectral Data Record.
Note that in the case of a cell containing a bifurcation, a ridge ending, or both, the cell
permutation shall be chosen purely on the basis of finding the closest matching candidate
cell structure with the information contained within the cell.
To prevent aliasing in the two-dimensional DFT, it could be desirable to window the
image prior to spectral decomposition. One useful window is the two dimensional
Gaussian. Closely related to the Gaussian windowed DFT is the application of Gabor
filters of predetermined wavelength and direction to the image. This standard
accommodates the reporting of Gabor amplitudes for each of the selected filters on each
cell.
5.4 Quality
For each group of cells defined above, a quality parameter provides an indication of the
quality of the information in that group of cells, with higher numbers indicating better
quality. A quality granularity parameter will specify the number of cells in a Cell Quality
Group: for example a value of 1 indicates a group comprises 1x1 cells; and a value of 2
indicates that a group comprises 2x2 cells. Some factors that contribute to the quality of
the finger pattern cell information are gray scale resolution, gray scale linearity, spatial
distortions, and location of the finger core within the raw fingerprint image.
ISO/IEC CD 19794-3
6 Finger Pattern Spectral Data Record
6.1 Introduction
The finger pattern spectral data record format is used to provide interoperability between
fingerprint recognition systems using spectral data in some way. The record format
contains both public and extended (proprietary) finger pattern spectral interchange data.
With the exception of the Format Identifier and the Version number for the standard,
which are null-terminated ASCII character strings, all data is represented in binary format.
There are no record separators or field tags; fields are parsed by byte count. The
biometric data record specified in this standard shall be embedded in a CBEFF-compliant
structure in the CBEFF Biometric Data Block (BDB).
The BDB_PID shall be defined by CBEFF. The CBEFF BDB_biometric_organization
shall be assigned by the International Biometric Industry Association (IBIA) to JTC 1 SC
37 shall be used. This is the sixteen bit value 0x0101 (hexadecimal 101 or decimal 257).
There are two different CBEFF BDB_format codes codes assigned to this standard: one
for a record without an extended data portion, and one for a format with the extended
data portion. If the record has no extended data, the associated CBEFF BDB_format shall
be the sixteen-bit value 0x0301; if the record has an extended area, the associated CBEFF
BDB_format shall be the sixteen-bit value 0x0302.
The organization of the record is as follows:
A fixed-length (49 bytes) Record Header containing information about the overall record,
including the number of fingers represented and the overall record length in bytes;
A single Finger Pattern Spectral Data Record for each finger, consisting of:
Fixed length header (8 bytes) containing information about the data for a single finger
Finger pattern spectral interchange data block (the block of cell data is followed by a
block of quality data).
Extended data block - containing vendor-specific data.
ISO/IEC CD 19794-3
Record
Header
Finger Pattern
Interchange Data
Extended
Data
Finger Pattern Data Record
Finger Pattern
Record Header
Finger Pattern
Record Header
Finger Pattern
Interchange Data
Finger Pattern 1
All multi-byte quantities are represented in Big-Endian format; that is, the more
significant bytes of any multibyte quantity are stored at lower addresses in memory than
(and are transmitted before) less significant bytes. All numeric values are fixed-length
integer quantities, and are unsigned quantities.
6.2 Record Header
There shall be one and only one record header for the finger pattern spectral record, to
hold information describing the identity and characteristics of device that generated the
data.
6.2.1 Format Identifier
For this standard, the Format Identifier shall consist of three characters "FPR" followed
by the null character (0x0).
6.2.2 Version Number
The version number for the version of this standard used in constructing the pattern
spectral record shall be placed in four bytes. This version number shall consist of three
ASCII numerals followed by a zero byte as a NULL string terminator. The first and
second character will represent the major revision number and the third
character will represent the minor revision number. Upon approval of this specification,
the version number shall be " 10" (an ASCII space followed by an ASCII '1' and an
ASCII '0').
6.2.3 Length of Record
The length of the entire record shall be recorded in four bytes.
ISO/IEC CD 19794-3
6.2.4 Capture Device ID
The Capture Device ID shall be recorded in two bytes. A value of all zeros will be
acceptable and will indicate that the Capture Device ID is unreported.
6.2.5 Number of Finger Patterns in Record
The total number of finger patterns in the record shall be contained in 1 byte.
6.2.6 Resolution of Finger Pattern in x-direction
The resolution (in ppcm) of the finger image(s) in the x-direction shall be record in 2
bytes. The stored valued shall be ROUND(ppcm).
6.2.7 Resolution of Finger Pattern in y-direction
The resolution (in ppcm) of the finger images(s) in the y-direction shall be record in 2
bytes. The stored valued shall be ROUND(ppcm).
6.2.8 Number of Cells in x-direction
The number of finger pattern cells in the x-direction shall be recorded in 1 byte.
6.2.9 Number of Cells in y-direction
The number of finger pattern cells in the y-direction shall be recorded in 1 byte.
6.2.10 Number of Pixels in Cells in x-direction
The number of pixels in the x-direction of each cell shall be recorded in 2 bytes.
6.2.11 Number of Pixels in Cells in y-direction
The number of pixels in the y-direction of each cell shall be recorded in 2 bytes.
6.2.12 Cellular x-offset
The number of pixels in the x-direction of the finger image before the first cell shall be
recorded in 1 byte.
6.2.13 Cellular y-offset
The number of pixels in the y-direction of the finger image before the first cell shall be
recorded in 1 byte.
ISO/IEC CD 19794-3
6.2.14 Number of Pixels between Cell Centers in x-direction
The number of pixels in the x-direction of the finger image between centers of adjacent
or overlapping cells. This will require 1 byte.
6.2.15 Number of Pixels between Cell Centers in y-direction
The number of pixels in the y-direction of the finger image between centers of adjacent
or overlapping cells. This will require 1 byte.
6.2.16 Number of Components Extracted from each cell
Number of DFT components or filters applied to each cell. Not all of these components
are necessarily stored in the record. This will require 2 bytes.
6.2.17 Type of window
This field will specify any window used on the cells prior to spectral decomposition and
the window parameters. In the case of Gabor filtering, this field will specify Gaussian
window and give the value of the single Gaussian parameter, σ, in units of pixels. Multiscale
windowing parameters will not be accommodated. This will require 2 bytes.
6.2.18 Wavelength and angle generating mechanism for each filter
This field is used for specifying the wavelength parameters of the Gabor filters used on
the cells. Values for all of the filter outputs might not be saved, however, in the record.
Multi-scale Gabor filtering will not be accommodated. In the case of two-dimensional
DFT, this field can simply indicate DFT. This will require 1 byte.
6.2.19 Method for selecting retained components
This field will specify retention of all components, the K highest energy components or
components above a threshold energy. This will require 1 byte.
6.2.20 Naming and ordering of retained components
In the case where only some of the spectral components are retained, it will be necessary
to specify the meaning of each of the stored components. Example of data in the field –
(Spatial wavelength, magnitude, propagation angle, magnitude, phase angle, magnitude)
or (x wavelength, complex magnitude, y wavelength, complex magnitude). This will
require 1 byte.
6.2.21 Bit-depth of Cell Structure Angle
The bit-depth used to represent the Cell Structure Angle shall be recorded in 1 byte.
ISO/IEC CD 19794-3
6.2.22 Bit-depth of Cell Structure Wavelength
The bit-depth used to represent the Cell Structure Wavelength shall be recorded in 1 byte.
6.2.23 Bit-depth of Cell Structure Phase Offset
The bit-depth used to represent the Cell Structure Phase Offset shall be recorded in 1 byte.
6.2.24 Bit-depth of Cell Structure Quality
The bit-depth used to represent the Cell Structure Quality shall be recorded in 1 byte.
6.2.25 Cell Quality Granularity
The granularity of the cell quality shall be recorded in 1 byte. The granularity is
calculated as SQRT(Number of Cells in Cell Quality Group).
6.2.26 Reserved Bytes
Two bytes are reserved for future revision of this specification. For Version 1.0 of this
standard, these byte values must be set to 0.
6.3 Single Finger Pattern Spectral Record Format
6.3.1 Finger Pattern Record Header
A finger header shall start each section of finger data providing information for that
finger. There shall be one finger header for each finger contained in the finger pattern
spectral record. The finger header will occupy a total of eight bytes as described below.
6.3.1.1 Finger Location
The finger location shall be recorded in one byte. The codes for this byte shall be as
defined in Table 5 of ANSI/NIST-ITL 1-2000, "Data Format for the Interchange of
Fingerprint Information". This table is reproduced here in Table 1 for convenience. Only
codes 0 through 10 shall be used; the "plain" codes are not relevant for this standard.
Table 1 - Finger Location Codes
Finger location Code
Unknown finger 0
Right thumb 1
Right index finger 2
Right middle finger 3
Right ring finger 4
Right little finger 5
Left thumb 6
ISO/IEC CD 19794-3
Left index finger 7
Left middle finger 8
Left ring finger 9
Left little finger 10
Plain right thumb 11
Plain left thumb 12
Plain right four 13
Plain left four fingers 14
6.3.1.2 Impression type
The impression type of the finger image(s) shall be recorded in this one byte field.
Nonlive entries refer to images scanned from cards or other media. These codes are
compatible with Table 4 of ANSI/NIST-ITL 1-200, "Data Format for the Interchange of
fingerprint Information", with the addition of the "swipe" type. The swipe type identifies
templates derived from the image streams generated by sliding the finger linearly across a
small sensor surface. Only codes 0 through 3 and 8 shall be used; the "latent" codes are
not relevant for this standard.
Table 2 - Finger impression type
Description Code
Live-scan plain 0
Live-scan rolled 1
Nonlive-scan
plain
2
Nonlive-scan
rolled
3
Latent impression 4
Latent tracing 5
Latent photo 6
Latent lift 7
Swipe 8
Reserved 9
6.3.1.3 Number of Views in Finger Pattern
Some systems may have more than one finger record for the same finger. Each of these
records represents a different view of the finger. The total number of views within each
Finger Pattern Record shall be recorded in 1 byte.
6.3.1.4 Finger Pattern Quality
The quality of the overall finger pattern shall be between 0 and 100 and recorded in one
byte. This quality number is an overall expression of the quality of the finger pattern. A
value of 0 shall represent the lowest possible quality and the value 100 shall represent the
highest possible quality. The numeric values in this field will be set in accordance with
ISO/IEC CD 19794-3
the general guidelines contained in Section 2.1.42 of ANSI/INCITS 358-2002, "BioAPI
H-Level Specification Version 1.1". Further, a quality value of 101 indicates that the raw
image from which the finger pattern was derived complied with Appendix F of the
Electronic Fingerprint Transmission Specification
(http://www.fbi.gov/hq/cjisd/iafis/efts_70.pdf).
6.3.1.5 Length of Data Block
The total length of the finger data block (including the extended data) shall be contained
in 2 bytes.
6.3.2 Finger Pattern Spectral Data
6.3.2.1 Finger Pattern Spectral Interchange Data
6.3.2.1.1 View Number
Preceding the Finger Pattern Cell Data is the View Number, which is a number starting
from 0 that sequentially identifies each of the views of a finger contained in this finger
pattern record. The view number shall be recorded in 1 byte.
6.3.2.1.2 Finger Pattern Spectral Data
The Finger Pattern Spectral Data shall be stored in a packed format with the data
corresponding to the upper left cell stored first, followed by the cell on right of this first
cell, and so on until the first row and then subsequent rows are stored.
6.3.2.1.3 Cell Quality Data
The Cell Quality Data shall follow the Finger Pattern Spectral Data and shall be stored in
an identical manner, starting with the upper left value.
6.3.3 Extended Data
The extended data section of the finger pattern spectral record is open to placing
additional data that may be used by the matching equipment. The size of this section
shall be kept as small as possible, augmenting the data stored in the standard finger
pattern section. The extended data for each finger view shall immediately follow the
standard finger pattern spectral data for that finger view and shall begin with the
Extended Data Block Length field. More than one extended data area may be present for
each finger and the extended data block length field will be the summation of the lengths
of each extended data segment. The data block length is used as a signal for the existence
of the extended data while the individual extended data length fields are used as indices
to parse the extended data. Note that the extended data area cannot be used alone,
without the standard portion of the finger pattern spectral record.
ISO/IEC CD 19794-3
6.3.3.1 Extended Data Fields
6.3.3.1.1 Extended Data Block Length
All finger pattern spectral interchange data records shall contain the extended data block
length. This field will signify the existence of extended data. A value of all zeros
(0x0000 hexadecimal) will indicate that there is no extended data and that the file will
end or continue with the next finger view. A nonzero value will indicate the length of all
extended data starting with the next byte. The block length (6.3.3.1.1) will then be
followed by the type identification code (6.3.3.1.2), length of data field (6.3.3.1.3) and
the data area (6.3.3.1.4). This will require two bytes.
6.3.3.1.2 Extended Data Area Type Code
The type identification code shall be recorded in two bytes, and shall distinguish the
format of the extended data area (as defined by the Vendor specified by the PID code in
the CBEFF header). A value of zero in both bytes is a reserved value and shall not be
used. A value of zero in the first byte, followed by a non-zero value in the second byte,
shall indicate that the extended data section has a format defined in this standard. A nonzero
value in the first byte shall indicate a vendor specified format, with a code
maintained by the vendor. Refer to Table 3 for a summary of the type identification
codes. If the Extended Data Block Length (6.3.3.1.1) for the finger view is zero,
indicating no extended data, this field shall not be present.
Table 3 - Extended Data Area Type Codes
First byte Second byte Identification
0x00 0x00 Reserved
0x00 0x01 reserved
0x00 0x02 core and delta data (Section 6.3.3.3)
0x00 0x03 Reserved
0x00 0x04-0xFF Reserved
0x01-0xFF 0x00 Reserved
0x01-0xFF 0x01-0xFF vendor-defined extended data
6.3.3.1.3 Extended Data Area Length
The length of the extended data section, including the vendor identification and length of
data fields, shall be recorded in two bytes. This value is used to skip to the next extended
data if the matcher cannot decode and use this data. If the Extended Data Block Length
(6.3.3.1.1) for the finger view is zero, indicating no extended data, this field shall not be
present.
ISO/IEC CD 19794-3
6.3.3.1.4 Data Section
The data field of the extended data is defined by the equipment that is generating the
finger pattern spectral record, or by the core and delta extended data format contained in
this standard. If the Extended Data Block Length (6.3.3.1.1) for the finger view is zero,
indicating no extended data, this field shall not be present.
6.3.3.2 Core and Delta Data Format
If the extended data area type code is 0x0002, the extended data area contains core and
delta information. This format is provided to contain optional information about the
placement and characteristics of the cores and deltas on the original fingerprint image.
Core and delta points are determined by the overall pattern of ridges in the fingerprint.
There may be one or more core points and zero or more delta points for any fingerprint.
Core and delta points may or may not include angular information.
The core and delta information shall be represented as follows. The first byte shall
contain the core information type and the number of core points included; legal values are
0 or greater. This length byte shall be followed by the position and angular information
for the cores. The next byte shall contain the delta information type and the number of
delta points included; legal values are 0 or greater. This length byte shall be followed by
the position and angular information for the deltas.
6.3.3.2.1 Core Information Type
The core information type shall be recorded in the first two bits of the upper byte of the
number of cores. The bits “01” will indicate that the core has angular information while
“00” will indicate that no angular information is relevant for the core type. If this field is
“00”, then the angle fields shall not be present for the cores.
6.3.3.2.2 Number of Cores
The number of core points represented shall be recorded in the least significant four bits
of this byte. Valid values are from 0 to 15.
6.3.3.2.3 Core Position
The x coordinate of the core shall be recorded in the lower fourteen bits of the first two
bytes (fourteen bits). The y coordinate shall be placed in the lower fourteen bits of the
following two bytes. The coordinates shall be expressed in pixels at the resolution
indicated in the record header.
6.3.3.2.4 Core Angle
The angle of the core shall be recorded in one byte in units of 1.40625 (360/256) degrees.
The value shall be a non-negative value between 0 and 255, inclusive. For example, an
angle value of 16 represents 22.5 degrees. If the core information type is zero (see
Section 6.3.3.2.1), then this field shall not be present.
ISO/IEC CD 19794-3
6.3.3.2.5 Delta Information Type
The delta information type shall be recorded in the first two bits of the upper byte of the
number of deltas. The bits “01” will indicate that the delta has angular information while
“00” will indicate that no angular information is relevant for the delta type. If this field is
“00”, then the angle fields shall not be present for the deltas.
6.3.3.2.6 Number of Deltas
The number of delta points represented shall be recorded in the least significant four bits
of this byte. Valid values are from 0 to 15.
6.3.3.2.7 Delta Position
The X coordinate of the delta shall be recorded in the lower fourteen bits of the first two
bytes (fourteen bits). The Y coordinate shall be placed in the lower fourteen bits of the
following two bytes. The coordinates shall be expressed in pixels at the resolution
indicated in the record header.
6.3.3.2.8 Delta Angles
The three angle attributes of the delta shall each be recorded in one byte in units of
1.40625 (360/256) degrees. The value shall be a non-negative value between 0 and 255,
inclusive. For example, an angle value of 16 represents 22.5 degrees. If the delta
information type is zero (see Section 6.3.3.2.5), then this field shall not be present.
ISO/IEC CD 19794-3
6.3.3.2.9 Core and Delta Format Summary
The core and delta format shall be as follows:
6.3.3.2.1 6.3.3.2.2 6.3.3.2.3 6.3.3.2.3 6.3.3.2.4
Core info
type
# of cores Reserved X location Reserved Y location Core Angle … … …
type # cores reserved x coordinate reserved y coordinate angle … … …
2 bits 6 bits 2 bits 14 bits 2bits 14 bits 1 byte 5 bytes
1 byte 2 bytes 2bytes only present if
core info type
not zero
zero or more
additional cores
6.3.3.2.5 6.3.3.2.6 6.3.3.2.7 6.3.3.2.7 6.3.3.2.8
Delta info
type
# of deltas Reserved X location Reserved Y location Delta Angles … … …
Type # deltas reserved x coordinate reserved y coordinate ang1 ang2 ang3 … … …
2 bits 6bits 2 bits 14 bits 2 bits 14 bits 3 bytes 5 bytes
1 byte 2 bytes 2 bytes only present if
delta info type
not zero
zero or more
additional
deltas
ISO/IEC CD 19794-3
Table 4. Summary of Finger Pattern Spectral Data Record
Record Header
Field Size Valid values Reference
Format Identifier 4 bytes 0x46505200
('F 'P 'R 0x0)
6.2.1
Version Number 4 bytes 6.2.2
Length of Record 4 bytes 6.2.3
Capture Device ID 2 bytes 6.2.4
Number of Finger
Patterns in Record
1 byte 1-255 6.2.5
Resolution of finger
pattern in x-direction
ROUND(ppcm)
2 bytes 1-788 6.2.6
Resolution of finger
pattern in y-direction
ROUND(ppcm)
2 bytes 1-788 6.2.7
Number of Cells in
x-direction
2 bytes 1-(size of finger
pattern in x-
direction)
6.2.8
Number of Cells in
y-direction
2 bytes 1-(size of finger
pattern in y-
direction)
6.2.9
Number of Pixels in
Cells in x-direction
2 bytes 1-(size of finger
pattern in x-
direction)
6.2.10
Number of Pixels in
Cells in y-direction
2 bytes 1-(size of finger
pattern in y-
direction)
6.2.11
Cellular x-offset 2 bytes 0- (size of finger
pattern in x-
direction)
6.2.12
Cellular y-offset 2 bytes 0- (size of finger
pattern in y-
direction)
6.2.13
Number of Pixels
between Cell
Centers in x-
direction
2 bytes 0– (size of finger
pattern in x-
direction)
6.2.14
Number of Pixels
between Cell
Centers in y-
direction
2 bytes 0– (size of finger
pattern in x-
direction)
6.2.15
ISO/IEC CD 19794-3
Number of
components
extracted from each
cell
2 bytes 1– (total number of
pixels in the cell)
6.2.16
Type of window and
parameter
2 bytes Name of window
and controlling
parameters
6.2.17
Wavelength and
angle generating
mechanism for
filters
1 byte Starting spatial
wavelength and
delta wavelength,
or listing of
wavelengths;
starting angle and
delta angle, or
listing of angles
6.2.18
Method of selecting
retained components
1 byte All, top k energy,
components above
an energy thr eshold
6.2.19
Naming and
ordering of retained
components
1 byte Naming of
component
descriptors and
component values
6.2.20
Bit-depth of Cell
Structure Angle
1 byte 1-8 6.2.21
Bit-depth of Cell
Structure
Wavelength
1 byte 1-8 6.2.22
Bit-depth of Cell
Structure Phase
Offset
1 byte 1-8 6.2.23
Bit-depth of Cell
Structure Quality
1 byte 1-8 6.2.24
Cell Quality
Granularity
1 byte 1-8 6.2.25
Reserved Bytes 2 bytes 6.2.26
Finger Pattern Spectral Record Header
Field Size Values Reference
Finger Location 1 byte 0-11 Table 1
Impression Type 1 byte 0-5 Table 2
Number of Views in
Finger Pattern
Record
1 byte 0-255 6.3.1.3
Fingerprint Pattern
Quality
1 byte 0-100 6.3.1.4
ISO/IEC CD 19794-3
Length of data block
(in bytes) including
extended data
2 bytes 6.3.1.5
Extended Data
Block Length
2 bytes 6.3.3.1.1
Finger Pattern Spectral Data
Field Size Content Reference
View Number 1 byte 6.3.2.1.1
Finger pattern
spectral Cell Data
6.3.2.1.2
Cell Quality Data 6.3.2.1.3
Finger pattern
spectral Extended
Data
6.3.3
ISO/IEC CD 19794-3
7 Annex A (informative) - Finger Pattern Spectral Data Record Example 1
This informative annex provides an example of finger pattern spectral interchange data.
A.1 Reduction in Resolution
An example of a re-sampled image is shown below in figure 5, where an original
128x128 image, sampled at 98.5 ppcm (250 ppi), is first cropped to 120x120 pixels and
then re-sampled to 78.8 ppcm (200 ppi), to produce an image of dimensions 96x96 pixels.
ISO/IEC CD 19794-3
A.2 Cellular Representation
In this example, the cellular representation of the finger pattern spectral data comprises
dividing the central portion (at an offset of 13 pixels in the x-direction and 8 pixels in the
y-direction) of the finger pattern into a grid of cells of dimension 5x5 pixels. Therefore,
the cellular representation grid contains 14x16 cells, which represents an image area of
70x80 pixels, or 8.9x10.1 mm. At each cell the finger pattern will be represented by one
of 1024 different cell structures, as described below.
A.3 Cell Structure
Each of the candidate cell structures for representing the local finger pattern spectral data
at each cell is defined by a two dimensional cosinusoidal pattern (see figures 7)
ISO/IEC CD 19794-3
The range and resolution of each of these parameters for this example is given below:
θ: 0 to 180 degrees (16 equal increments - i.e. 4 bits of information).
λ: 0 to 7/8 of the wavelength of the Maximal Spatial Frequency (8 increments - i.e. 3 bits
of information). Therefore, for this 78.8 ppcm (200 ppi) example, a spatial frequency of 0
to 3.4 line pairs per mm is represented).
δ: 0 to 315 degrees (8 equal increments - i.e. 3 bits of information). In this example, each
of the finger pattern cells is represented by the most similar of the 1024 (16x8x8)
permutations of cell structure. Therefore, each cell structure requires 10 bits of data
storage (reduced from 5x5x8 bits = 200 bits per cell). In this manner, each of the finger
pattern cells is represented by one of the 1024 permutations of cell structure. The
resulting data will comprise the majority of the public portion of the Finger Pattern
Spectral Data Record. In this example, the finger pattern is represented by 14x16x10 bits
(14 cells by 16 cells by 10 bits), which requires 280 bytes of storage.
A.4 Quality
A value of 2 indicates that a group comprises 2x2 cells. For the example stated here with
14x16 cells, and a quality granularity of 2 (2x2 cells), 56 quality parameter values will be
required, at a bit-depth of 4, thus adding 28 bytes to the interchange data.
ISO/IEC CD 19794-3
A.5 Data Record
For the example stated here, the data record comprises the following values and occupies
a total of 365 bytes:
Table 5. Finger Pattern Spectral Data Record
Record Header
Field Size Value
Format Identifier 4 bytes 0x46505200
('F 'P 'R 0x0)
Version Number 4 bytes
Length of Record 4 bytes 365
Capture Device ID 2 bytes
Number of Finger
Patterns in Record
1 byte 1
Image Resolution of
finger pattern in x-
direction
ROUND(ppcm)
2 bytes 79
Image Resolution of
finger pattern in y-
direction
ROUND(ppmm)
2 bytes 79
Number of Cells in
x-direction
2 bytes
14
Number of Cells in
y-direction
2 bytes 16
Number of Pixels in
Cells in x-direction
2 bytes 5
Number of Pixels in
Cells in y-direction
2 bytes 5
Cellular x-offset 2 bytes 13
Cellular y-offset 2 bytes 8
Number of Pixels
between Cell
Centers in x-
direction
2 bytes 5
Number of Pixels
between Cell
Centers in y-
direction
2 bytes 5
Number of
components
extracted from each
cell
2 bytes 16
ISO/IEC CD 19794-3
Type of window and
parameter
2 bytes G,3
Wavelength and
angle generating
mechanism for
filters
1 bytes 14 (only spatial
wavelength), 0
(Starting angle),
11.3 degrees (delta
angle)
Method of selecting
retained components
1 byte top 1 energy
Naming and
ordering of
components
1 byte Angle, wavelength,
phase
Bit-depth of Cell
Structure Angle
1 byte 4
Bit-depth of Cell
Structure
Wavelength
1 byte 3
Bit-depth of Cell
Structure Phase
Offset
1 byte 3
Bit-depth of Cell
Structure Quality
1 byte 4
Cell Quality
Granularity
1 byte 2
Reserved Bytes 2 byte
Field Size Value
Finger Location 1 byte 2
Finger Impression 1 byte 0
View Number 1 byte 0
Fingerprint Pattern
Quality
1 byte 80
Length of data block
(in bytes) including
private data
2 bytes 308
Extended Data
Block Length
2 bytes 0
Finger Pattern Cell
Data
308 bytes
Finger pattern
spectral Extended
Data
0 bytes
ISO/IEC CD 19794-3
8 Annex B (informative) - Finger Pattern Spectral Data Record Example 2
This informative annex provides an example of finger pattern spectral interchange data
for a global DFT on a 400x600 pixel image with retention of all components to allow
lossless invertibility.
B.1 Cell structure
In this example, there is one cell for each finger view. The 400 x 600 pixel images are
padded with zeros equally on left and right sides and equally top and bottom to create a
512x1024 image. A global DFT is performed with retention of all components 512x512
complex components to allow lossless invertibility. There will be no windowing.
The Nyquist number of components will be generated (in this case 512). Selection
criteria will be all Nyquist frequencies, N. All 524,288 components will be retained as
complex (C) coefficients (requiring TBD bytes of storage each).
Table 6. Finger Pattern Spectral Data Record
Record Header
Field Size Value
Format Identifier 4 bytes 0x46505200
('F 'P 'R 0x0)
Version Number 4 bytes
Length of Record 4 bytes TBD
Capture Device ID 2 bytes
Number of Finger
Patterns in Record
1 byte 1
Image Resolution of
finger pattern in x-
direction
ROUND(ppcm)
2 bytes 79
Image Resolution of
finger pattern in y-
direction
ROUND(ppmm)
2 bytes 79
Number of Cells in
x-direction
2 bytes
1
Number of Cells in
y-direction
2 bytes 1
Number of Pixels in
Cells in x-direction
2 bytes 512
Number of Pixels in
Cells in y-direction
2 bytes 1024
Cellular x-offset 2 bytes 0
Cellular y-offset 2 bytes 0
ISO/IEC CD 19794-3
Number of Pixels
between Cell
Centers in x-
direction
2 bytes 0
Number of Pixels
between Cell
Centers in y-
direction
2 bytes 0
Number of
components
extracted from each
cell
2 bytes 524,288
Type of window and
parameter
2 bytes 0
Wavelength and
angle generating
mechanism for
filters
1 byte Nyquist
Method of selecting
retained components
1 byte All
Naming and
ordering of
components
1 byte x-wavelength,
complex amplitude,
y-wavelength,
complex amplitude
Bit-depth of Cell
Structure Angle
1 byte 4
Bit-depth of Cell
Structure
Wavelength
1 byte 3
Bit-depth of Cell
Structure Phase
Offset
1 byte 3
Bit-depth of Cell
Structure Quality
1 byte 4
Cell Quality
Granularity
1 byte 2
Reserved Bytes 2 byte
Field Size Value
Finger Location 1 byte 2
Finger Impression 1 byte 0
Number of Views 1 byte 1
View Number 1 byte 0
Fingerprint Pattern
Quality
1 byte 80
ISO/IEC CD 19794-3
Length of data block
(in bytes) including
private data
2 bytes TBD
Extended Data
Block Length
2 bytes 0
ISO/IEC CD 19794-3
9 Annex C (informative) - Finger Pattern Spectral Data Record Example 3
This informative annex provides an example of finger pattern spectral interchange data
for a ridge flow field extracted on a 400x600 pixel image using Gabor filters on 15x15
regions with 7 pixel overlap.
C.1 Cell structure
In this example, there are 53 cells in the x-direction and 80 cells in the y-direction for one
finger view. 18 Gabor filters are used with wavelength of 14 pixels and Gaussian
parameter of 3 pixels. Angle of rotation of successive filters is 10 degrees, starting from
0 degrees, as shown in Figure 7. Only the angle of rotation of the filter with highest
energy will be retained, but 90 degrees will be added to this angle so that the ridge flow,
not the filter orientation, will be indicated.
Table 7. Finger Pattern Spectral Data Record
Record Header
Field Size Value
Format Identifier 4 bytes 0x46505200
('F 'P 'R 0x0)
Version Number 4 bytes
Length of Record 4 bytes 2177
Capture Device ID 2 bytes
Number of Finger
Patterns in Record
1 byte 1
Image Resolution of
finger pattern in x-
direction
ROUND(ppcm)
2 bytes 79
Image Resolution of
finger pattern in y-
direction
ROUND(ppmm)
2 bytes 79
Number of Cells in
x-direction
2 bytes
53
Number of Cells in
y-direction
2 bytes 80
Number of Pixels in
Cells in x-direction
2 bytes 15
Number of Pixels in
Cells in y-direction
2 bytes 15
Cellular x-offset 2 bytes 0
Cellular y-offset 2 bytes 0
Number of Pixels
between Cell
Centers in x-
direction
2 bytes 7
ISO/IEC CD 19794-3
Number of Pixels
between Cell
Centers in y-
direction
2 bytes 7
Number of
components
extracted from each
cell
2 bytes 18
Type of window and
parameter
3 byte G, 3
Wavelength and
angle generating
mechanism for
filters
2 bytes 14
Method of selecting
retained components
1 byte Top energy
Naming and
ordering of
components
1 Angle + 90 degrees
Bit-depth of Cell
Structure Angle
1 byte 4
Bit-depth of Cell
Structure
Wavelength
1 byte 0
Bit-depth of Cell
Structure Phase
Offset
1 byte 0
Bit-depth of Cell
Structure Quality
1 byte 0
Cell Quality
Granularity
1 byte 0
Reserved Bytes 2 byte
Field Size Value
Finger Location 1 byte 2
Finger Impression 1 byte 0
Number of Views 1 byte 1
View Number 1 byte 0
Fingerprint Pattern
Quality
1 byte 0
Length of data block
(in bytes) including
private data
2 bytes 2120
Extended Data
Block Length
2 bytes 0