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dwt_svd.m
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dwt_svd.m
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%% DWT - SVD Watermarking
function [psnr_values, psnr2dB_values] = dwt_svd()
% clear workspace
clear all;
close all;
clc;
%change directory
folder_name = uigetdir(pwd, 'Select Directory Where the .m Files Reside');
if ( folder_name ~= 0 )
if ( strcmp(pwd, folder_name) == 0 )
cd(folder_name);
end
else
return;
end
% read cover image & watermark logo
[cover_fname, cover_pthname] = ...
uigetfile('*.jpg; *.png; *.tif; *.bmp', 'Select the Cover Image');
if (cover_fname ~= 0)
cover_image = strcat(cover_pthname, cover_fname);
cover_image = double( rgb2gray( imread( cover_image ) ) );
cover_image = imresize(cover_image, [512 512], 'bilinear');
else
return;
end
[watermark_fname, watermark_pthname] = ...
uigetfile('*.jpg; *.png; *.tif; *.bmp', 'Select the Watermark Logo');
if (watermark_fname ~= 0)
watermark_logo = strcat(watermark_pthname, watermark_fname);
watermark_logo = double( im2bw( rgb2gray( imread( watermark_logo ) ) ) );
watermark_logo = imresize(watermark_logo, [512 512], 'bilinear');
else
return;
end
% Set constant variables
numOfKeys = 20;
gaussian_plot = true;
print_figures = false;
if (gaussian_plot == false)
secret_key = 3; % random secret key
watermarked_image = watermark_embedding(cover_image, watermark_logo, ...
secret_key, print_figures);
watermark_extraction(watermarked_image, watermark_logo, secret_key, ...
print_figures, true);
else
% Set function parameters to not print any plots and not to do any
% signature authentication
% print_figures = false;
% Pre-allocate matrices
psnr_values = zeros(1, numOfKeys);
psnr2dB_values = zeros(1, numOfKeys);
decoded_correct = zeros(1, numOfKeys);
decoded_wrong = zeros(1, numOfKeys);
% [m, n] = size(watermark_logo);
% correctWatermarkDiff = zeros(1, m*n);
wrongWatermarkDiff = zeros(1, length(watermark_logo));
for key = 1:numOfKeys
% Embedding with the right key
[watermarked_image, original_signature] = ...
watermark_embedding(cover_image, watermark_logo, key, print_figures);
watermarked_images_dir = strcat(pwd, '\watermarked_images\', num2str(key), '.png');
imwrite(uint8(watermarked_image), watermarked_images_dir, 'png');
% Transform the original watermrak (i.e. the original signature) to
% the interval [-1, 1]
original_signature(find(original_signature == 0)) = -1;
% Measure the degree of distortion of the original and the watermarked
% image using PSNR (dB)
psnr_values(key) = psnr(cover_image, watermarked_image);
psnr2dB_values(key) = pow2db(psnr_values(key));
% Detection with the right key, message_correct is actually the
% watermark_logo because in essence that's what I'm hidding in the
% cover image. Whereas the watermark_correct is actually the signature
% which helps in the detection of false acceptance and false
% rejection
[~, ~, recon_sig_corr, LL4, HH4] = ...
watermark_extraction(watermarked_image, watermark_logo, key, ...
print_figures, true);
% transform the watermark_correct(i.e. the reconstructed_signature)
% and the watermark_wrong(i.e. the wrong reconstructed signature)
% to the interval [-1, 1]
recon_sig_corr(find(recon_sig_corr == 0)) = -1;
LL4 = LL4(:)';
HH4 = HH4(:)';
LL4 = LL4 - mean(LL4);
HH4 = HH4 - mean(HH4);
comb_HH4_LL4 = [LL4 HH4];
% decoded_correct(key) = (abs(comb_HH4_LL4) * recon_sig_corr')/512^2;
% decoded_correct(key) = sum(comb_HH4_LL4 .* recon_sig_corr)/512^2;
% Detection with the wrong key
[~, watermark_wrong, recon_sig_wrng, LL4wr, HH4wr] = ...
watermark_extraction(watermarked_image, watermark_logo, key+11, ...
print_figures, false);
watermark_wrong(find(watermark_wrong == 0)) = -1;
LL4wr = LL4wr(:)';
HH4wr = HH4wr(:)';
LL4wr = LL4wr - mean(LL4wr);
HH4wr = HH4wr - mean(HH4wr);
combwr_HH4_LL4 = [LL4wr HH4wr];
% decoded_wrong(key) = (abs(combwr_HH4_LL4) * watermark_wrong')/512^2;
% decoded_wrong(key) = sum(watermark_wrong .* original_signature)/512;
% Keep track of the correlation between the watermark_correct and
% the watermark_wrong
correlation_correct = corrcoef(comb_HH4_LL4, recon_sig_corr);
decoded_correct(key) = correlation_correct(2, 1);
correlation_wrong = corrcoef(combwr_HH4_LL4, watermark_wrong);
decoded_wrong(key) = correlation_wrong(2, 1);
% Calculate the difference between the correct extracted watermarks and
% the original watermark and the wrong extracted watermarks and the orignal
% correctKeyWatermarkDiff(key, :) = watermark_wrong - original_signature;
wrongWatermarkDiff(key, :) = watermark_wrong - original_signature;
clear('watermark_correct', 'comb_HH4_LL4', 'watermark_wrong', ...
'combwr_HH4_LL4', 'original_signature', ...
'LL4', 'HH4', 'LL4wr', 'HH4wr');
% Clear workspace
clear('watermark_logo_row', 'watermark_logo_extracted_correct', ...
'watermark_logo_extracted_wrong', 'watermarked_image', ...
'watermark_correct', 'watermark_wrong', 'message_correct', ...
'message_wrong', 'watermarked_image');
end
meanOfDecodCorr = mean(decoded_correct);
stdOfDecodCorr = std(decoded_correct);
meanOfDecodWrng = mean(decoded_wrong);
stdOfDecodWrng = std(decoded_wrong);
gaussians(meanOfDecodCorr, stdOfDecodCorr, meanOfDecodWrng, stdOfDecodWrng);
[Pfa, Pfr] = PfaPfr(meanOfDecodCorr, stdOfDecodCorr, meanOfDecodWrng, stdOfDecodWrng, numOfKeys);
% Measure bit error rate, and plot against threshold T of pfa,
% where T = pfa/pfr. Or equivalently plot BER & E versus pfa
BER = BitErrorRate(wrongWatermarkDiff);
end
end