Summary of the June 3, 1993,

Compression Review Group Meeting

R. T. Moore

Representative, IAI

In compliance with Motion #1 of the NIST Workshop on the Electronic Exchange of Fingerprint Images held on March 4-6, 1992, the

fourth meeting of the Compression Review Group was held at NIST.

This meeting took place in Gaithersburg, MDon June3, 1993. Organizations represented were the FBI, UK Home Office, IAI, NIDL, and

NIST. Nine individuals were present including three from the Latent

Fingerprint Section of the FBI.

Tests are currently being planned by the Latent Working Group at

the FBI to examine displayed images for the purpose of investigating

scanning resolutions and compression ratios as relates to image quality.

In order to give members of the Compression Review Group an opportunity to review output images from the WSQ algorithm, a demonstration of this algorithm has been scheduled for June 23, 1993, at the FBI.

Original images and the reconstructed versions of the compressed images will be displayed on the monitor so that any differences between

the images can be observed.

Los Alamos and NIST are independently developing encoder and

decoder implementations of the WSQ algorithm. Both of these implementations are extensions of the original WSQ algorithm developed

at the FBI. In addition to the compression algorithm itself, these implementations will address several format variations described in the

February, 1993, version of the “WSQ Gray-Scale Fingerprint Image

Compression Specification”. Within the next few months these implementations are expected to be completed and test images will be

exchanged between the two organizations. Comparisons of the outputs

of the encoder and decoder portions of the two implementations will be

performed to validate the implementations.

When this testing phase is concluded, a notice will be placed in the

Commerce Business Daily (CBD) inviting commercial vendors to participate in the testing procedures. These vendors will be able to exJ. Forensic Ident.

524 /43 (5), 1993
Summary of the June 3, 1993,

Compression Review Group Meetin

R. T. Moore

Representative, IAI

In compliance with Motion #1 of the NIST Workshop on the E

tronic Exchange of Fingerprint Images held on March 4-6, 1992

fourth meeting of the Compression Review Group was held at N

This meeting took place in Gaithersburg, MDon June3, 1993. Org

zations represented were the FBI, UK Home Office, IAI, NIDL, 

NIST. Nine individuals were present including three from the L

Fingerprint Section of the FBI.

Tests are currently being planned by the Latent Working Grou

the FBI to examine displayed images for the purpose of investiga

scanning resolutions and compression ratios as relates to image qua

In order to give members of the Compression Review Group an op

tunity to review output images from the WSQ algorithm, a demon

tion of this algorithm has been scheduled for June 23, 1993, at the 

Original images and the reconstructed versions of the compressed 

ages will be displayed on the monitor so that any differences betw

the images can be observed.

Los Alamos and NIST are independently developing encoder 

decoder implementations of the WSQ algorithm. Both of these 

plementations are extensions of the original WSQ algorithm develo

at the FBI. In addition to the compression algorithm itself, these 

plementations will address several format variations described in 

February, 1993, version of the “WSQ Gray-Scale Fingerprint Im

Compression Specification”. Within the next few months these 

plementations are expected to be completed and test images wil

exchanged between the two organizations. Comparisons of the out

of the encoder and decoder portions of the two implementations wi

performed to validate the implementations.

When this testing phase is concluded, a notice will be placed in 

Commerce Business Daily (CBD) inviting commercial vendors to 

ticipate in the testing procedures. These vendors will be able to 

J. Forensic Ident.

524 /43 (5), 1993
The image quality of reconstructed output images will be dependent

on the quality of the input. The decompressed output from a poorly

inked impression can never have abetter level of image quality than the

input. The scanners used to input images will have a strong impact of

the output. In the future, scanned images will originate from AFIS

scanners, card scanners, and live-scan equipment.

The key ingredient to obtaining well compressed and high quality

images is the use of good scanners and other equipment which satisfy

the requirements for fingerprint identification. Recently, a new version

of the Image Quality Specification for equipment was released by the

FBI. This document states the engineering specifications that scanners

and other equipment must meet or exceed in order to produce images

which are acceptable to the FBI.

The main criteria for scanners is the Modulation Transfer Function

(MTF) rather than line-pairs per millimeter, as was used in the past.

The MTF method checks the performance of a system by measuring the

response of the system at all lp/mm ratings between low and high

values of lp/mm. As a more complete and comprehensive approach to

measuring behavior, it is a curve of values taken at various lp/mm. As

a result, MTF provides a better characterization of system performance

than obtainable using a single-value of lp/mm. However, it may require specialized hardware and software to perform the analysis. On

the other hand, checking the MTF response at a single value of lp/mm

selected near the upper limit of the system response curve provides a

method of evaluating performance based on visual observation. It is

expected that the response at smaller values of lp/mm would be better

than this, but the actual values are not determined. Using the MTF

obtained at a high value of lp/mm should insure good performance at

the lower values.

Scanners that adhere to the provisions of this specification should be

able to capture high-quality data which will result in high-quality images being electronically stored.

The last part of the meeting was a demonstration by NIDL of the

concept for an “electronic loupe”. This is an electronic device which,

when developed, will provide the fingerprint examiner with the added

ability to view electronic fingerprint images at a 1:1 scale. By mimicking the optical loupe, the “electronic loupe” will display side-by-side

images in an environment familiar to the fingerprint examiner. The

J. Forensic Ident.

526 /43 (5), 1993
The image quality of reconstructed output images will be depen

on the quality of the input. The decompressed output from a p

inked impression can never have abetter level of image quality tha

input. The scanners used to input images will have a strong impa

the output. In the future, scanned images will originate from A

scanners, card scanners, and live-scan equipment.

The key ingredient to obtaining well compressed and high qu

images is the use of good scanners and other equipment which sa

the requirements for fingerprint identification. Recently, a new ve

of the Image Quality Specification for equipment was released b

FBI. This document states the engineering specifications that scan

and other equipment must meet or exceed in order to produce im

which are acceptable to the FBI.

The main criteria for scanners is the Modulation Transfer Fun

(MTF) rather than line-pairs per millimeter, as was used in the 

The MTF method checks the performance of a system by measurin

response of the system at all lp/mm ratings between low and 

values of lp/mm. As a more complete and comprehensive approa

measuring behavior, it is a curve of values taken at various lp/mm

a result, MTF provides a better characterization of system perform

than obtainable using a single-value of lp/mm. However, it may 

quire specialized hardware and software to perform the analysis

the other hand, checking the MTF response at a single value of lp

selected near the upper limit of the system response curve provid

method of evaluating performance based on visual observation. 

expected that the response at smaller values of lp/mm would be b

than this, but the actual values are not determined. Using the M

obtained at a high value of lp/mm should insure good performan

the lower values.

Scanners that adhere to the provisions of this specification shou

able to capture high-quality data which will result in high-quality 

ages being electronically stored.

The last part of the meeting was a demonstration by NIDL o

concept for an “electronic loupe”. This is an electronic device wh

when developed, will provide the fingerprint examiner with the a

ability to view electronic fingerprint images at a 1:1 scale. By mim

ing the optical loupe, the “electronic loupe” will display side-by

images in an environment familiar to the fingerprint examiner. 

J. Forensic Ident.

526 /43 (5), 1993
FULLSIZE DISPLAY

ELECTRONIC

LOUPE

, 1 n

USE ELECTRONIC LOUPE

WHEN A 1:1 DISPLAY

IS REQUIRED

Figure 2

Side-by-side images magnifiedto 5:1 or greater and displayedon

full size monitors are usually completely adequate for ten-print examinerstoperform their identification comparisons. However, attimes, the

latent examiner needs to compare similar details oftwo images froma

much smaller area of interest than the total fingerprint image provides.

For these occasions, use of a full size display does not allow the

examiner to make this comparison in a familiar setting. A tool to

display those details in the same manner as available with an optical

loupe would be quite valuable. The “electronic loupe” is intended to

fulfill this function.

Figure 2 illustrates the planned use of the “electronic loupe”. A fill

size monitor simultaneously displays a latent image and a file image.

Many of the identification characteristics can be located on this display.

When additional detail is required, the same images can be viewed at a

1:1 display on the “electronic loupe”. This will provide the examiner

with a means of accurately focusing on details of interest from both the

file and latent images.

J. Forensic Ident.

528 /43 (5), 1993