Frog localization
In this stage, the gray level frog image is thresholded to obtain a bi-nary image by usingOtsu's adaptive thresholding method (Otsu, 1979).
Otsu's method searches exhaustively for the threshold that minimizes
the intra-class variance (the variance within the class), defined as a
weighted sum of variances of the two classes:
σ
2
P T ðÞ¼P1 T ðÞσ
2
1 T ðÞþP2 T ðÞσ
2
T ðÞ ð1