Face Detection and Modeling for Recognition - Biometrics Research ...

(a) (b) (c)
Figure 5.8. Interacting snakes: (a) face region extracted from a face image shown
in Fig. 5.4(a); (b) image in (a) overlaid with a (projected) semantic face graph; (c)
the initial configuration of interacting snakes obtained from the semantic face graph
shown in (b).
strength) extracted from an image. In addition to minimizing the internal energy of
an individual curve, interacting snakes minimize the attraction energy on both the
contours and enclosed regions of individual snakes, and the repulsion energy among
multiple snakes.
The energy functional used by interacting snakes is described in
Eq. (5.7).
E isnake =
⎡
N∑ ⎢
⎣
i=1
∫ 1
0
E internal (v i (s)) + E repulsion (v i (s))
} {{ }
E prior
⎤
+ E attraction (v i (s))
} {{ }
E observation
ds⎦ , (5.7)
where i is the index of the interacting snake. The first two energy terms are based on
the prior knowledge of snake’s shape and snakes’ configuration (i.e., facial topology)
while the third energy term is based on the sensed image (i.e., observed pixel values).
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