71477212FFT.rar_图像 FFT _图像FFT_图像变换

function X=MYFFT(x,N) %x:series;N,the number of fft-complex required,which must be a power of2 %X:output the fft of x %----------------------------------------------------------- nargchk(1,2,nargin); if nargin<2% N=length(x); elseif N<=0%input must be a nonnegtive integer error('N must be a nonnegtive integer'); end num=log2(N);%N is a power of 2 ??? if (num/ceil(num)~=1)%case:No disp('N isnot a power of 2!');%message N=(2^ceil(num));%modify N % x=[x,zeros(1,N-length(x))];%zero-padding end if length(x)<N disp('Zero-padding was used!'); x=[x,zeros(1,N-length(x))];%zero-padding end [m,n]=size(x); if m<n x=x.'; end %----------------------------------------------------------- id=bitinv(N);%call subprogram x_temp=x(id+1);%reshaped series num=log2(N);%the No. of recycle NUM=N;%the total No. of x that want to be compute for K=1:num n=2^K;%xlh's or xfh's length idpublic=1:2^K:N;%public id Xbin=[];%initial for I=1:NUM/2%divide x to NUM/2 parts idbegin=idpublic(I);%2*(I-1)+2^(K-1);%first id tn=n/2;%id1=;id2=id1+n/2; id1=idbegin+(0:(tn-1));id2=idbegin+((tn):2*tn-1); xfh=x_temp(id1); xlh=x_temp(id2); Xbin(1:id2(end),1)=[Xbin;fft2_subs(xfh,xlh)]; end NUM=floor(NUM/2); x_temp=Xbin;%x_temp changed end %----------------------------------------------------------------- function Xbins=fft2_subs(xfh,xlh) r=length(xfh);ns=2*r;% in order to decide Wn Wn=exp(-j*2*pi/ns); k=(0:length(xlh)-1)'; Xbins(:,1)=[xfh+xlh.*Wn.^k;xfh-xlh.*Wn.^k]; end %---------------------------------------------------------------- function id=bitinv(N) %该程序也可以由Matlab中的bitrevord()代替 %N:number,it must be a power of 2; %id,output the index of the sery to caculate fft if N<0 error('input must be a nonnegtive integer!'); end n=ceil(log2(N));%No. of bits needed to represent the index index=0:2^n-1;%index of the series binvec=zeros(1,n); id=binvec; for i=1:2^n binvec(i,:)=fliplr(dec2binvec(index(i),n)); id(i)=binvec2dec(binvec(i,:)); end end %------------------------------------------------------------ X=Xbin;% end