function Idown = dsample(I,N)
[row,col] = size(I);
drow = round(row/N);
dcol = round(col/N);
Idown = ones(drow,dcol);
p =1;
q =1;
for i = 1:N:row
for j = 1:N:col
Idown(p,q) = I(i,j);
q = q+1;
end
q =1;
p = p+1;
end
end
%¸更改主程序部分
adata=dsample(adata,2);%降采样系数为2
adata=dsample(adata,4);%K=4
adata=dsample(adata,8);%K=8
abs_fft_correct_adata2(:,:)=abs_fft_correct_adata(1:sp/4,:)-40;
abs_fft_correct_adata2(:,:)=abs_fft_correct_adata(1:sp/8,:)-40;
abs_fft_correct_adata2(:,:)=abs_fft_correct_adata(1:sp/16,:)-40;