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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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Fig. 23.4: The delta <strong>and</strong> the core points in fingerprint images.<br />

23.3.2 Classification Based on Singular Points<br />

Delta point<br />

Core point<br />

A point is detected as an ordinary point, core point or delta point by<br />

computing the poincare index. Poincare index is computed by summing up<br />

the changes in the direction angle around the curve, when making a full<br />

counterclockwise turn around the curve in a directional image [15]; the<br />

directional angle turns 0 degree, +180 degree, -180 degree during this trip. A<br />

point is called ordinary if the angle has turned 0 degree, core if it has turned<br />

+180 degree <strong>and</strong> delta if it has turned –180 degree.<br />

Depending upon the number of core-delta pairs they can be categorized<br />

into Arch (core-delta pair =0), Tented arch / Loop (core-delta pair = 1) or<br />

Whorl /Twin loop (core-delta pair =2). If the number of core-delta pair is<br />

greater than two then further processing is to be done to identify the exact<br />

class.

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