Fig. 9

The fingerprint OF smoothing: a original image affected by several horizontal creases, b result of the conventional gradient based method [13], c the OF digitized as two-orientation-zones, d the filtering result of (c) after removing holes, e the result of two-orientation-zone filtering, f the border lines of the two-orientation-zone, g the OF digitized as three-orientation-zone, h the filtering result of (g) after removing holes, i the result of three-orientation-zone filtering