Fig. 1. 3×3 neighbors in WLD region

Fig. 2. Three different neighborhoods of WLD. (a) n=3, K=4; (b) n=5, K=8; (c) n=7, K=12

Fig. 3. Enhancement examples. (a) Some original finger-vein images; (b) enhanced results using 3×3 blocks with 4 orientations (n=3); (c) enhanced results using 5×5 blocks with 8 orientations (n=5); (d) enhanced results using 7×7 blocks with 12 orientations (n=7)

Fig. 4. Finger-vein ROI images. (a) Data-1; (b) Data-2

Fig. 5. Enhancement methods with different combinations of Gabor and WLD. (a) Data-1; (b) Data-2

Fig. 6. ROC curves of different enhancement methods. (a) Data-1; (b) Data-2

Fig. 7. ROC curves of different comparison methods. (a) Data-1; (b) Data-2