function [dis]= dis_peak(I1)
I = abs(I1);
pvt=5;


[r, c]=find(I==max(I(:)));

r =r(1); c=c(1);
r1=r; c1= c;


I(r-pvt:r+pvt, c-pvt:c+pvt)=0;


[r, c]=find(I==max(I(:)));
r =r(1); c=c(1);
r2=r; c2= c;
I(r-pvt:r+pvt, c-pvt:c+pvt)=0;


[r, c]=find(I==max(I(:)));
r =r(1); c=c(1);
r3=r; c3= c;
I(r-pvt:r+pvt, c-pvt:c+pvt)=0;

[r1, c1, r2, c2, r3, c3]
dis=sqrt((r2-r3)^2+(c2-c3)^2)

dis= size(I1,2)*2/dis