ruanyuzhi.rar_donoho阈值_小波 阈值_小波分解_小波系数_软阈值

levels=3; img=imread('lena.bmp'); img=double(img(:,:,1)); [m,n]=size(img); % 加噪 norm_img=img/255; noise_img=imnoise(norm_img,'speckle',0.05); noise_img=255*noise_img; figure(1) imshow(noise_img,[]) psnr1=10*log10(m*n*255^2/sum(sum((noise_img-img).^2))) noise_img=255*log(noise_img+1)/log(256); % 二维小波正变换 [m,n]=size(img); ca=noise_img; out_img=noise_img; for i=1:levels [ca,ch,cv,cd] = dwt2(ca,'bior4.4','mode','per'); out_img(1:m,1:n)=[ca,ch;cv,cd]; m=m/2; n=n/2; end figure(2) imshow(out_img,[]) out_img=threshold_2_N(out_img,levels); %二维小波逆变换 levels=3; [m,n]=size(out_img); m=m/2^levels; n=n/2^levels; ca=out_img(1:m,1:n); re_img=out_img; for i=1:levels ch=out_img(1:m,(n+1):2*n); cv=out_img((m+1):2*m,1:n); cd=out_img((m+1):2*m,(n+1):2*n); ca=idwt2(ca,ch,cv,cd,'bior4.4','mode','per'); m=2*m; n=2*n; end re_img=ca; re_img=round(exp(re_img*log(256)/255)-1); re_img=max(0,min(re_img,255)); figure(3) imshow(re_img,[]) [m,n]=size(img); psnr2=10*log10(m*n*255^2/sum(sum((re_img-img).^2)))