function [row,col]=randinterval(matrix,count,key)

[m,n]=size(matrix);
interval1=floor(m*n/count)+1;
interval2=interval1-2;
if interval2==0
    error('載體太小不能將秘密信息隱藏進(jìn)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('載體太小不能將秘密信息隱藏進(jìn)去！');
        end
        c=mod(c,n);
        if c==0
            c=1;
        end
    end
    row(1,i)=r;
    col(1,i)=c;
end