%給定一個原始圖像
load geometry;
nbcol=size(map,1);
colormap(pink(nbcol));
figure(1);
image(wcodemat(X,nbcol));
title('原始圖像');
%================================
%設置延拓模式為補零方式，對圖像應用小波sym4進行3層分解，然后重構第3層近似
lev=3;
wname='sym4';
dwtmode('zpd'); 
[c,s]=wavedec2(X,lev,wname);
a=wrcoef2('a',c,s,wname,lev);
figure(2);
image(wcodemat(a,nbcol));
%================================
%改變延拓模式為對稱延拓且同樣應用小波sym4將原始圖像分解到第3層，之后重構第3層近似
dwtmode('sym');
[c,s]=wavedec2(X,lev,wname);
aa=wrcoef2('a',c,s,wname,lev);
figure(3);
image(wcodemat(aa,nbcol));
%================================
%設置平滑填補的延拓模式，應用小波sym4對原始圖像進行3層分解，然后重構第3層近似
dwtmode('spd');
[c,s]=wavedec2(X,lev,wname);
aaa=wrcoef2('a',c,s,wname,lev);
figure(4);
image(wcodemat(aaa,nbcol));