B=imread（‘Image000.bmp‘）;
imshow（B）
k=-0.2;r=35;
choice=1;
B=B（::1）;
[HW]=size（B）;
B=padarray（B[r?r]‘symmetric‘‘both‘）;
H_p=H+2*r;
W_p=W+2*r;
C=false（H_pW_p）;
switch?choice
????case?1
????????for?i=1+r:H+r;
????????????for?j=1+r:W+r;
????????????????ai=i-floor（r/2-1/2）;
????????????????bi=i+floor（r/2）;
????????????????aj=j-floor（r/2-1/2）;
????????????????bj=j+floor（r/2）;
????????????????m_ij=mean（mean（B（ai:biaj:bj）））;
????????????????s=double（B（ai:biaj:bj））-m_ij;
????????????????s=mean（mean（s.^2））;
????????????????s=sqrt（s）;
????????????????T=m_ij+k*s;
????????????????if?double（B（ij）>T）
????????????????C（ij）=1;
????????????????end