小波分析理论与Matlab实现

clear; %装入原图像1 load woman; I=X; %小波函数 type = 'db1'; % 2维离散Daubechies小波变换 [CA1, CH1, CV1, CD1] = dwt2(I,type); C1 = [CH1 CV1 CD1]; %系数矩阵大小 [length1, width1] = size(CA1); [M1, N1] = size(C1); % 定义阈值T1 T1 =50; alpha = 0.2; %在图像中加入水印 for counter2 = 1: 1: N1 for counter1 = 1: 1: M1 if( C1(counter1, counter2) > T1 ) marked1(counter1,counter2) = randn(1,1); NEWC1(counter1, counter2) = double( C1(counter1, counter2) ) +... alpha * abs( double( C1(counter1, counter2) ) ) * marked1(counter1,counter2) ; else marked1(counter1, counter2) = 0; NEWC1(counter1, counter2) = double( C1(counter1, counter2) ); end; end; end; %重构图像 NEWCH1 = NEWC1(1:length1, 1:width1); NEWCV1 = NEWC1(1:length1, width1+1:2*width1); NEWCD1 = NEWC1(1:length1, 2*width1+1:3*width1); R1 = double( idwt2(CA1, NEWCH1, NEWCV1, NEWCD1, type) ); %分离水印 watermark1 = double(R1) - double(I); figure(1); subplot(1,2,1); image(I); axis('square'); title('原始图像'); subplot(1,2,2); imshow(R1/250); axis('square'); title('Daubechies小波变换后图像'); figure(2); imshow(watermark1*10^16); axis('square'); title('水印图像'); % 水印检测 newmarked1 = reshape(marked1, M1*N1, 1); % 检测阈值 T2 = 60; for counter2 = 1: 1: N1 for counter1 = 1: 1: M1 if( NEWC1(counter1, counter2) >T2 ) NEWC1X(counter1, counter2) = NEWC1(counter1, counter2); else NEWC1X(counter1, counter2) = 0; end; end; end; NEWC1X = reshape(NEWC1X, M1*N1, 1); correlation1 = zeros(1000,1); for corrcounter = 1: 1: 1000 if( corrcounter == 500) correlation1(corrcounter,1) = NEWC1X'*newmarked1 / (M1*N1); else rnmark = randn(M1*N1,1); correlation1(corrcounter,1) = NEWC1X'*rnmark / (M1*N1); end; end; % 计算阈值 originalthreshold = 0; for counter2 = 1: 1: N1 for counter1 = 1: 1: M1 if( NEWC1(counter1, counter2) > T2 ) originalthreshold = originalthreshold + abs( NEWC1(counter1, counter2) ); end; end; end; originalthreshold = originalthreshold * alpha / (2*M1*N1); corrcounter = 1000; originalthresholdvector = ones(corrcounter,1) * originalthreshold; figure(3); plot(correlation1, '-'); hold on; plot(originalthresholdvector, '--'); title('原始的加水印图像'); xlabel('水印'); ylabel('检测响应');