內容：

matlab編程小波變換進行圖像去噪處理，包括各種軟硬閾值的選取函數，%小波閾值去噪

clear all

clc;

f=imread('graylena.bmp');

f=double(f);

s=size(f);

r=imnoise2('gaussian',s(1),s(2),0,20);%填加高斯白噪聲

fnoisy=f+r;

%對圖像進行三層小波分解

[c,s]=wavedec2(fnoisy,3,'db8');

%cA3=appcoef2(c,s,'db8',3);

[cH3,cV3,cD3]=detcoef2('all',c,s,3);c3=[cH3,cV3,cD3];

[cH2,cV2,cD2]=detcoef2('all',c,s,2);c2=[cH2,cV2,cD2];

[cH1,cV1,cD1]=detcoef2('all',c,s,1);c1=[cH1,cV1,cD1];

%固定閾值(VisuShrink閾值)：thr=delta*sqrt(2*log(n));

delta=median(abs(cD1(:)))/0.6745;

thr1c=delta*thselect(c,'minimaxi');

%thr1c=delta*3.5;

%thr1c3=delta*thselect(c3,'sqtwolog');

%thr1c2=delta*thselect(c2,'sqtwolog');

%thr1c1=delta*thselect(c1,'sqtwolog');

n=[1 2 3];p=[thr1c thr1c thr1c];

dnc0=wthcoef2('h',c,s,n,p,'s');

dnc0=wthcoef2('v',dnc0,s,n,p,'s');

dnc0=wthcoef2('d',dnc0,s,n,p,'s');

dnf0=waverec2(dnc0,s,'db8');

%基于Stein的無偏似然估計原理的自適應閾值(SUREShrink閾值)：

%thr1cA3=thselect(cA3,'rigrsure');

%thr1=surethr(c,delta);

%最優預測變量閾值：

%極大極小閾值：thr=0.3936+0.1829*(log(n)/log(2));

%figure,subplot(221),imshow(dnf0,[]), ('VisuShrink閾值')

origif=cacupsnr(fnoisy,f)

%VSf0=cacupsnr(dnf0,f)

figure,subplot(121),imshow(f,[]), ('原始圖像')

subplot(122),imshow(fnoisy,[]), ('加噪圖像')

dnc1=wthresfunc(c,s,'hard',thr1c);

dnf1=waverec2(dnc1,s,'db8');

figure,subplot(221),imshow(dnf1,[]), ('硬閾值函數')

VSf1=cacupsnr(dnf1,f)

dnc2=wthresfunc(c,s,'soft',thr1c);

dnf2=waverec2(dnc2,s,'db8');

subplot(222),imshow(dnf2,[]), ('軟閾值函數')

VSf2=cacupsnr(dnf2,f)

dnc3=wthresfunc(c,s,'semisoft',thr1c);

dnf3=waverec2(dnc3,s,'db8');

subplot(224),imshow(dnf3,[]), ('折中閾值函數')

VSf3=cacupsnr(dnf3,f)

dnc4=wthresfunc(c,s,'halfsoft',thr1c);

dnf4=waverec2(dnc4,s,'db8');

subplot(223),imshow(dnf4,[]), ('半軟閾值函數')

VSf4=cacupsnr(dnf4,f)

dnc1=wthresfunc(c,s,'upsoft',thr1c);

dnf1=waverec2(dnc1,s,'db8');

figure,subplot(221),imshow(dnf1,[]), ('改進軟閾值函數')

VSf1=cacupsnr(dnf1,f)

dnc2=wthresfunc(c,s,'hfsmsoft',thr1c);

dnf2=waverec2(dnc2,s,'db8');

subplot(222),imshow(dnf2,[]), ('新閾值函數')

VSf2=cacupsnr(dnf2,f)

dnc3=wthresfunc(c,s,'newthr1',thr1c);

dnf3=waverec2(dnc3,s,'db8');

subplot(223),imshow(dnf3,[]), ('改進閾值函數一')

VSf3=cacupsnr(dnf3,f)

dnc4=wthresfunc(c,s,'newthr2',thr1c);

dnf4=waverec2(dnc4,s,'db8');

subplot(224),imshow(dnf4,[]), ('改進閾值函數二')

VSf4=cacupsnr(dnf4,f)