% 本程序先生成一个“Blocks”信号，然后加上高斯白噪声，再用'db3'小波进行分解，
% 以说明信号和噪声在各个尺度上的表现。
clear all;
% 生成“Blocks”信号
% M = 1/1024;
% N = 1/M;
% t =0:M:1-1/1024;
% TPoint = [0.1,0.13,0.15,0.23,0.25,0.40,0.44,0.65,0.76,0.78,0.81];
% h = [4,-5,3,-4,5,-4.2,2.1,4.3,-3.1,2.1,-4.2];
% [aaa,TSize] = size(TPoint);
% FBlock = zeros(N,1);
% for j = 1:N
% for i = 1:TSize
% if (t(j) - TPoint(i))> 0
% sgnt = 1;
% elseif (t(j) - TPoint(i))< 0
% sgnt = -1;
% else
% sgnt =0;
% end
% FBlock(j) = FBlock(j) +h(i)*(1+sgnt)/2;
% end
% end
%sig=FBlock';
FBlock = imread('lena.bmp')
% subplot(121)
figure(1)
imshow(FBlock)
title(' 原信号');
% grid on;
% 加上白噪声
% sigma=0.1;
% SNR=20.0;
% sig=awgn(FBlock,SNR,sigma);%原信号功率0.1加入白噪声
sig=imnoise(FBlock,'gaussian',0,0.01)
% subplot(122)
figure(2)
imshow(sig)
title(' 带噪信号');
grid on;
% 小波分解
[c,l]=wavedec(sig,2,'db3');
ca2=appcoef(c,l,'db3',2);%提取低频系数
cd2=detcoef(c,l,2);%高频系数
%ans=size(cd2);
cd1=detcoef(c,l,1);
% subplot(322)
% plot(cd1)
% subplot(324)
% plot(cd2)
% subplot(326)
% plot(ca2)
%只使用低频系数重构
dl=length(cd2)+length(cd1);
c1=[ca2;zeros(dl,1)];%为什么不能直接ca2在waverec中使用？？
y=waverec(c1,l,'db3');
%=========================
%使用低频系数与一级分解高频系数重构
% dl=length(cd2);
% c1=[ca2;zeros(dl,1);cd1];
% y=waverec(c1,l,'db3');
%=========================
%使用低频系数与二级分解高频系数重构
%=========================
% dl=length(cd1);
% c1=[ca2;cd2;zeros(dl,1)];
% y=waverec(c1,l,'db3');
%=========================
%=========================
% y=waverec(c,l,'db3');
%=========================
% subplot(325)
% plot(y)
figure(3)
imshow(FBlock)
