fg_10_13.m

英文书《Digital Signal Processing with Examples in MATLAB》附带的MATLAB实例

% fg_10_13     Image recovery via inverse DCT.
% Put the 256 x 256 image into x.
x=zeros(256,256);
fid=fopen('boats.txt');
for row=(1:256)
 x(1:256,row)=fscanf(fid, ...
  '%4d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d%5d\n',256);
end
fclose(fid);
x=x';
% X=DCT scaled to [0,255] with X(1)=0.
xavg=mean(x(:));
T=dct(x-xavg);
U=dct(T.');
V=U-min(U(:));
X=round(V*255/max(V(:)));
%X=V;
Hdct=entropy(X(:))
% xhat=inverse DCT.
V=X*max(V(:))/255;
U=V+min(U(:));
T=idct(U).';
xhat=idct(T)+xavg;

% Plots.
colormap(gray(256));
sp_fig(1);
axes('position',[.05,.2,.5,.5]);
image(x);
set(gca,'fontsize',14);
set(gca,'xtick',[1 128 256],'ytick',[1 128 256]);
title('Original','fontsize',16);
axis square;

axes('position',[.5,.2,.5,.5]);
image(xhat);
set(gca,'fontsize',14);
set(gca,'xtick',[1 128 256],'ytick',[1 128 256]);
title('Reconstruction','fontsize',16);
axis square;