Instructions

U.are.U SDK - Developer Guide 61
ActiveX
Identification and Comparison
Identify() identifies a single FMD against an array of FMDs. This function takes as inputs:
• A single view in an FMD
• An array of FMDs (each FMD can contain up to 16 views) to compare
• The desired number of candidates to return
• The threshold for False Positive Identification Rate (FPIR) that is permitted
and returns matches as an array of integer pairs which provide the finger index and view index of each match.
Each time a view has a score lower than the threshold FPIR, that view is marked as a possible candidate. Then when all
possible candidates are identified (i.e., they meet the threshold), they are ranked by their score. Finally, the function
returns as many candidates as requested, based on the candidates with the lowest dissimilarity score. For a discussion
of setting the threshold as well as the statistical validity of the dissimilarity score and error rates, consult NIST
Fingerprint Image Quality (NFIQ) on page 14.
Compare() takes two single views from two FMDs and returns a dissimilarity score indicating the quality of the
match.
The majority of applications should use the Identify method to implement both identification and verification.
However, in a few special cases, e.g., using multi-modal biometrics, or doing statistical risk assessment, the Compare
method allows you to compare two FMVs to determine their actual degree of dissimilarity. This is useful for accuracy
testing and diagnostics and is not intended to be used in final applications for actual fingerprint recognition. The
Compare method returns a dissimilarity score with values:
• 0 = fingerprints are NOT dissimilar (i.e., they MATCH perfectly).
• maxint (#7FFFFFFF or 2147483647) = fingerprints are completely dissimilar (i.e., DO NOT match).
• Values close to 0 indicate very close matches, values closer to maxint indicate very poor matches.
The table below shows the relationship between the scores returned from Compare and the false match error rates
observed in our test. The dissimilarity score distribution is estimated based on our internal testing, and may not be
representative of the actual rate that will be observed in deployment.
Enrollment
CreateEnrollmentFmd() creates and returns an enrollment FMD. The method takes as input:
• Which format to use, e.g., ANSI or ISO
•An ArrayList object containing the FMDs to enroll
The recommended sequence in which to enroll FMDs is to send CreateEnrollmentFmd() four captured FMDs
in an array. If four FMDs are not enough, you can capture an FID, convert it to an additional FMD, add it to the array
Dissimilarity Score False Match Rate
2147483 .1%
214748 .01%
21474 .001%
2147 .0001%
Function Description
Compare Compare two FMDs; supported formats are: Gold SDK, One Touch SDK, ANSI
and ISO.
Identify Identify an FMD: given an array of FMDs, this function returns an array of
candidates that match the original fingerprint (an FMV within an FMD) within the
threshold of error. Supported formats are: Gold SDK, One Touch SDK, ANSI and
ISO.