Require: images, $T_1^{\text{pr}}=0.38$, $T_2^{\text{pr}}=0.14$, weight parameter θ ∈ [0, 1]
1:	for each image I i (x, y) do
2:	convert image to 8‐bit gray‐scale
3:	calculate $T_1^i$ and $T_2^i$ as in Algorithm 1
4:	calculate $N_f^i=\left(1-\theta \right)\frac{T_1^i}{T_1^{\text{pr}}}+\theta \frac{T_2^i}{T_2^{\text{pr}}}$.
5:	end for