thresholdtestdemo.m

小波变换在不同的阈值下重构的测试演示程序

function thresholdtestdemo(imgname,wavename,level,deta)

%  thresholdtestdemo  小波变换在不同阈值下重构的测试演示程序
%  thresholdtestdemo(imgname,wavename,level,deta)
%  本程序作用:载入图像信号,使用小波变换,比较显示不同阈值下的重构图像及相关信息
%  输入: imgname   ----要装载的图像名称
%        wavename  ----变换小波名称
%        level     ----小波分解级数
%        deta      ----测试阈值增加值
%  缺省时:变换图像为color256.png, 1级db9小波变换 deta=5   

if nargin==0

    imgname='color256.png';

    wavename='db9';

    level=1;

    deta=5;

else 

    if  nargin==1

        wavename='db9';

        level=1;

        deta=5;

    else 

        if nargin==2

            level=1;

            deta=5;

        else 

            if nargin==3

                deta=5;

            end 

        end 

    end 

end 

%  读入的X中含有被装载的图像信号,map中含有被装载的color 

[X,map] = imread(imgname); 

%检测图像格式

if isempty(map)

    emp=1;

else 

    X=ind2rgb(X,map)*255;

    emp=0;

end 

if ndims(X)==3

    imgcolor=1;

    Xr=X(:,:,1);

    Xg=X(:,:,2);

    Xb=X(:,:,3);

else 

    imgcolor=0;

end 

  

info=imfinfo(imgname);

ss=round((info(1).FileSize)/1024);

sname=size(imgname);

orgname=imgname(1:sname(2)-4);

nfile=struct('name','');

X=double(X);

%画出原始图像 

figure(1);

subplot(2,3,1);

imshow(uint8(X));colormap(map);       

title(strcat(wavename,'小波变换阈值测试(',mat2str(level),'级)'));

xlabel(strcat('原始图像(Size: ',mat2str(ss),'KB)'));

axis square

%小波分解 

if imgcolor

    [Cr,Sr]=wavedec2(Xr,level,wavename);

    [Cg,Sg]=wavedec2(Xg,level,wavename);

    [Cb,Sb]=wavedec2(Xb,level,wavename);

    C(1,:)=Cr;

    C(2,:)=Cg;

    C(3,:)=Cb;   

else 

    [C,S]=wavedec2(X,level,wavename);

end 

%在不同阈值下测试 

T(1)=0;

for i=1:4

    %用0置换矩阵中绝对值小于阈值的数值 

    if T(i)>0

        C(find(abs(C)<=T(i)))=0;

        %C=wthresh(C,'h',T(i));

    end 

    %计算零的个数 

    zeronum(i)=prod(size(find(C==0))); 

    %重构不同阈值下图像 

    if imgcolor

        Cr=C(1,:);

        Cg=C(2,:);

        Cb=C(3,:);       

        Ar=waverec2(Cr,Sr,wavename);           

        Ag=waverec2(Cg,Sg,wavename);          

        Ab=waverec2(Cb,Sb,wavename); 

        A(:,:,1)=uint8(round(Ar));

        A(:,:,2)=uint8(round(Ag));

        A(:,:,3)=uint8(round(Ab));  

    else 

        A=waverec2(C,S,wavename);  

        A=uint8(round(A));

    end 

    %存贮新图像,图像名为原图像名+小波名+阈值大小 

    nfile(i).name=strcat(orgname,'_',wavename,'_',mat2str(T(i)),'.png');

    imwrite(A,nfile(i).name,'png');

    %获取图像大小信息 

    info=imfinfo(nfile(i).name);

    if info(1).FileSize>1024

        sfile(i)=round((info(1).FileSize)/1024);

        sunit='KB';

    else

        sfile(i)=info(1).FileSize;

        sunit='B';

    end        

    %画出重构图像 

    figure(1);

    subplot(2,3,i+1);

    imshow(uint8(A));                 

    title(strcat('阈值T=',int2str(T(i)),' (Size:',int2str(sfile(i)),sunit,')'));

    xlabel(strcat('系数含"0"数目=',int2str(zeronum(i))));

    axis square

    if i<3

        T(i+1)=T(i)+deta;

    else 

        if i==3

            T(i+1)=T(i)+2*deta;

        end 

    end; 

end 

%画出不同阈值对应的文件大小及系数为零的关系图 

if and(or(min(zeronum)>1000,zeronum(1)==0),zeronum(4)/1000>sfile(4))

    zeronum=zeronum/1000;

    overth=1;

else 

    overth=0;

end; 

subplot(2,3,6);

plot(T,zeronum,'-rs','LineWidth',1,...

                'MarkerEdgeColor','k',...

                'MarkerFaceColor','g',...

                'MarkerSize',5);

hold on;

plot(T,sfile,'-bs','LineWidth',1,...

                'MarkerEdgeColor','k',...

                'MarkerFaceColor','y',...

                'MarkerSize',5);

xlabel('                         阈值T '); 

meant=(zeronum(4)-sfile(4))/8;

if overth

    text(10,zeronum(4)+meant,'系数含"0"数目/1000');

else 

    text(10,zeronum(4)+meant,'系数含"0"数目');

end    

text(15,sfile(4)+meant,strcat('文件大小(',sunit,')'));

axis square