function[row,col]=randinterval(matrix,count,key); 
[m,n]=size(matrix); 
interval1=floor(m*n/count)+1; 
interval2=interval1-2; 
if interval2==0 
    error('载体太小不能将秘密信息隐藏进去！'); 
end 
rand('seed',key); 
a=rand(1,count); 
row=zeros([1 count]); 
col=zeros([1 count]); 
r=1; 
c=1; 
row(1,1)=r; 
col(1,1)=c; 
for i=2:count 
    if a(i)>=0.5 
        c=c+interval1; 
    else 
        c=c+interval2; 
    end 
    if c>n 
        r=r+1; 
        if r>m 
            error('载体太大不能将秘密信息隐藏进去！'); 
        end 
        c=mod(c,n); 
        if c==0 
            c=1; 
        end 
    end 
row(1,i)=r; 
col(1,i)=c; 
end