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A. Tefas , C. Kotropoulos, I. Pitas

A RISTOTLE U NIVERSITY OF T HESSALONIKI D EPARTMENT OF I NFORMATICS. F ACE A UTHENTICATION BASED ON M ATHEMATICAL M ORPHOLOGY. A. Tefas , C. Kotropoulos, I. Pitas. F RONTIERS OF M ATHEMATICAL M ORPHOLOGY. April 17-20, 2000, Strasbourg, France. O UTLINE. Introduction

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A. Tefas , C. Kotropoulos, I. Pitas

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  1. ARISTOTLE UNIVERSITYOF THESSALONIKI DEPARTMENTOF INFORMATICS FACE AUTHENTICATIONBASED ON MATHEMATICAL MORPHOLOGY A. Tefas, C. Kotropoulos, I. Pitas FRONTIERSOF MATHEMATICAL MORPHOLOGY April 17-20, 2000, Strasbourg, France

  2. OUTLINE • Introduction • Morphological techniques in elastic graph matching • Morphological elastic graph matching • Morphological signal decomposition • Experimental Results • Conclusions

  3. INTRODUCTION Face recognition has exhibited a tremendous growth for more than two decades. Face verification:“Given a reference facial image or images and a test one, decide whether the test face corresponds to the reference one”. Multi-modal person verification.

  4. INTRODUCTION • Elastic graph matching (EGM) exploits both the gray-level information and shape information. • The response of a set of 2D Gabor filters tuned to different orientations and scales is measured at the grid nodes in EGM. • Morphological elastic graph matching (MEGM) and morphological signal decomposition elastic graph matching (MSD-EGM) use the multi-scale morphological dilation-erosion and the morphological signal decomposition instead of Gabor filters.

  5. Local descriptors extracted at the nodes of a sparse grid: The objective is to minimize the cost function: MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Elastic Graph Matching Signal Similarity measure:

  6. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Definitions

  7. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Multi-scale dilation-erosion of an image by a structuring function: Feature vector located at a grid node:

  8. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Suitable structuring functions Scaled hemisphere: Flat: Circular paraboloid:

  9. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING

  10. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Output of multi-scale dilation-erosion for nine scales. The first nine pictures are dilated images and the remaining nine are eroded images.

  11. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING MORPHOLOGICAL SIGNAL DECOMPOSITION objective: i-th component: spine: maximal function: first spine: and

  12. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING MSD algorithm Step 1: initialization. Step 2: i-th level of decomposition. Step 3: calculate i-th component. Step 4: calculate reconstructed image.

  13. MORPHOLOGICAL TECHNIQUESIN ELASTIC GRAPH MATCHING Feature vector for MSD-EGM: Reconstructed images at nineteen levels of decomposition

  14. GRID MATCHING PROCEDURE (a) (b) (c) Grid matching procedure: (a) Model grid for person BP. (b) Best grid for test person BP after elastic graph matching with the model grid. (c) Best grid for test person BS after elastic graph matching with the model grid for person BP.

  15. DISCRIMINANT ANALYSIS TECHNIQUES Principal component analysis for feature dimension reduction. Linear discriminant analysis for feature selection. Discriminatory power coefficients based on Fisher linear discriminant function for node weighting. Support vector machines for node weighting.

  16. EXPERIMENTAL RESULTS M2VTS database The database contains 37 persons’ video data, which include speech consisting of uttering digits and image sequences or rotated heads. Four recordings (i.e., shots) of the 37 persons have been collected. Frontal facial images with uniform background were used for the experiments. Experimental protocol “Leave one out” principle. 5328 impostor and 5328 client claims.

  17. EXPERIMENTAL RESULTS Experimental protocol

  18. EXPERIMENTAL RESULTS Performance evaluation False acceptance (FA) occurs when an impostor claim is accepted. False rejection (FR) occurs when a client claim is rejected. Equal error rate (EER) is the operating state where FA rate=FR rate. Receiver operating characteristics (ROC) is the plot of FA rate versus FR rate.

  19. EXPERIMENTAL RESULTS Comparison of equal error rates for several authentication techniques in the M2VTS database.

  20. EXPERIMENTAL RESULTS

  21. PERFORMANCE OF MEGM IN XM2VTSdb XM2VTS database 295 persons (8 images per person) uniform background Experimental protocol Configuration I Training: 39800 impostor and 200 client claims Evaluation: 40000 impostor and 600 client claims Testing: 112000 impostor and 400 client claims Experimental protocol Configuration II Four training images for each client Evaluation: 40000 impostor and 400 client claims Testing: 112000 impostor and 400 client claims

  22. PERFORMANCE OF MEGM IN XM2VTSdb Receiver Operating Characteristics MEGM Configuration I Configuration II

  23. PERFORMANCE OF MEGM IN XM2VTSdb Rates at several FAR on XM2VTSdb in the two configurations of the experimental protocol. All rates are in %.

  24. CONCLUSIONS • Novel methods for image analysis into the elastic graph matching have been proposed. • They are based on multi-scale erosion dilation and morphological signal decomposition of the facial image. • Discriminant analysis was applied in order to enhance the performance of the proposed methods. • The experimental results indicated the success of the proposed methods in frontal face authentication.

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