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Fingerprint Analysis (part 2) Pavel Mr ázek

Fingerprint Analysis (part 2) Pavel Mr ázek. Local ridge frequency. Local ridge frequency. Image enhancement / binarization. General rule: Smooth along ridges Enhance ridge-valley contrast Separate fingerprint from background (segmentation) Various methods: Convolution PDEs

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Fingerprint Analysis (part 2) Pavel Mr ázek

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  1. Fingerprint Analysis (part 2) Pavel Mrázek

  2. Local ridge frequency

  3. Local ridge frequency

  4. Image enhancement / binarization • General rule: • Smooth along ridges • Enhance ridge-valley contrast • Separate fingerprint from background(segmentation) • Various methods: • Convolution • PDEs • Morphology • Gabor filters • …

  5. Gabor filters • Several orientations • Several frequencies • At each position, • select orientation • select frequency • filter using the appropriate Gabor filter

  6. Gabor filters

  7. Coherence enhancing shock filter • Shock filter: • Regularized:

  8. Coherence enhancing shock filter • Use direction estimate:w … dominant eigenvector of the structure tensor

  9. Coherence enhancing shock filter Examples

  10. Ridge thinning • Thinning: morphological operation • Pixel value set to background if ridge connectivity not affected • Structuring element: typically 3x3 window • 9 pixels, 512 possible configurations, look-up

  11. Singular point detection • Methods for core and delta detection: • Poincaré index • Irregularity of orientation field, curvature • Partitioning of orientation field • Reliability problems

  12. Texture features

  13. Feature extraction summary Extract features, store a template • Prepare representation useful for matching • minutiae • … • Reduce memory requirements(typical size 500 B – 30 kB) • Privacy: fingerprint not stored

  14. Enrollment • Register user, store data into a database

  15. Verification • Compare to enrolled template,accept / reject a match

  16. Identification • Recover identity, 1-to-N match

  17. References • Maltoni et al.: Handbook of Fingerprint Recognition. Springer 2003. • Maltoni. A tutorial on fingerprint recognition. In LNCS 3161, Springer 2005. • Hong, Wan, Jain. Fingerprint image enhancement: algorithm and performance evaluation. IEEE PAMI 1998. • Zhou, Gu. A model-based method for the computation of fingerprints’ orientation field. IEEE TIP 2004. • Weickert. Coherence enhancing shock filters. DAGM 2003. • Contact: mrazekp -at- cmp.felk.cvut.cz

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