Extraction and Using Methods of Directional Information in Fingerprint Identification Preprocessing Algorithm

Directional map represents the basic structural feature of fingerprint really and abstractly, so it has very important research value in automated fingerprint identification system. The paper systematically introduced the calculation and smoothness of point directional map and block directional map, and how to realize oriented filtering to enhance image. In this paper, we used the predefine direction approach to compute point directional map, and a lowpass filter was applied to modifying the incorrect ridge directions. In order to improve the robust performance of the routine algorithm based on single-window, an improved method based on multi-window for computing block directional map was proposed. Considering that fingerprint is a kind of textured pattern, we used oriented filter based on block directional map to enhance images. To verify the performance of improved algorithm, contrastive experiment was conducted with routine algorithm. The results show that the set of algorithm is effective, especially to the fingerprint of poor quality.