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Master Thesis - Department of Computer Science

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(a) (b)<br />

Figure A.16: Thinned fingerprint images marked with minutiae.<br />

by square box and ridge endings by a ”+” sign. Minutiae directions are marked with<br />

an arrow (→) sign.<br />

A.6 Minutiae Matching<br />

The matching is done using Elastic graph matching as proposed by Ratha et al. [100].<br />

The output <strong>of</strong> this stage is a matching score which says the goodness <strong>of</strong> the matching.<br />

There are three main steps involved in this process:<br />

1. Registration,<br />

2. Minutiae Pairing, and<br />

3. Matching Score Computation.<br />

A.6.1 Registration<br />

In order to match two point sets with unknown orientation, scale, and translation,<br />

the two point sets must be registered with respect to each other. The orientation,<br />

scale, and translation parameters are estimated using a generalized Hough Transform<br />

[8].<br />

The input to the registration algorithm consists <strong>of</strong> two sets <strong>of</strong> minutiae points P<br />

and Q extracted from two fingerprint images. They are denoted by,<br />

P = �<br />

(p 1 x, p 1 y, α 1 ), ....., (p P x , p P y , α P ) �<br />

,<br />

139

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