stegocombine.m

stegenogrpahy in matlab based on dwt

% file name 'stegocombine.m'
% Run through Matlab

% By: Louis Casillas, [e-mail]

% Input:
% tree_path.jpg (RGB)
% wolverine.jpg (RGB)

% Output:
% displays these two images combined and the restored wolverine 
% image pulled from the combined image

% How:
% resizes wolverine.jpg to the size of tree_path.jpg,
% adds the resized wolverine image to tree_path.jpg by weighted values
% specified by WEIGHTED_COMBINE_VALUE:
% combined_image = tree_path + (wolverine_resized * WEIGHTED_COMBINE_VALUE)
% then tries to restore the wolverine image by subtracting the original
% tree_path.jpg values from the combined_image values and dividing by
% WEIGHTED_COMBINE_VALUE:
% restored_wolverine_image = (tree_path - combined_image) / WEIGHTED_COMBINE_VALUE

% the percent used to multiply the wolverine.jpg color values by before
% adding them to tree_path.jpg
% 1.0 = 100%
WEIGHTED_COMBINE_VALUE = 0.01;

% false => only display combined image and restored image
% true => display all images
DISPLAY_INTERMEDIATE_IMAGES = false;

% set DISPLAY_TESTING_IMAGES to a number below to run those tests
% extra tests will show how the wolverine image is restored from the 
% combined image for these 3 cases:
% 0 => no extra tests
% 1 => if the combined image is resized
% 2 => if the combined image is stored as a heavily compressed .jpg
% 3 => if the combined image has added noise
% 4 => show all tests
DISPLAY_TESTING_IMAGES = 4;

% load the images
original_tree_path_image = imread( 'tree_path.jpg' );
original_wolverine_image = imread( 'wolverine.jpg' );

% grab the x and y resolution for tree_path.jpg
tree_path_x_size = size( original_tree_path_image, 2 );
tree_path_y_size = size( original_tree_path_image, 1 );

% grab the x and y resolution for wolverine.jpg
original_wolverine_x_size = size( original_wolverine_image, 2 );
original_wolverine_y_size = size( original_wolverine_image, 1 );

if DISPLAY_INTERMEDIATE_IMAGES

    % display the original tree_path.jpg
    figure, imshow( original_tree_path_image ); title( 'Original - tree_path.jpg' );

    % display the original wolverine.jpg
    figure, imshow( original_wolverine_image ); title( 'Original - wolverine.jpg' );
end

% resize wolverine.jpg to be the same same as tree_path.jpg
resized_wolverine_image = imresize( original_wolverine_image, [tree_path_y_size, tree_path_x_size] );

if DISPLAY_INTERMEDIATE_IMAGES
    
    % display the resized wolverine.jpg
    figure, imshow( resized_wolverine_image ); title( 'Resized Wolverine' );
end

% create a blank image the same size as tree_path.jpg
% this will store the new image that is a combination of tree_path.jpg and
% wolverine.jpg
combined_image = zeros( tree_path_y_size, tree_path_x_size, 3 );

% add tree_path.jpg and wolverine.jpg but only give the pixels in
% the resized wolverine.jpg a weighted value determined by
% WEIGHTED_COMBINE_VALUE
for x_value = 1:tree_path_x_size
    for y_value = 1:tree_path_y_size
        combined_image( y_value, x_value, 1 ) = original_tree_path_image( y_value, x_value, 1 ) + (resized_wolverine_image( y_value, x_value, 1 ) * WEIGHTED_COMBINE_VALUE);
        combined_image( y_value, x_value, 2 ) = original_tree_path_image( y_value, x_value, 2 ) + (resized_wolverine_image( y_value, x_value, 2 ) * WEIGHTED_COMBINE_VALUE);
        combined_image( y_value, x_value, 3 ) = original_tree_path_image( y_value, x_value, 3 ) + (resized_wolverine_image( y_value, x_value, 3 ) * WEIGHTED_COMBINE_VALUE);
    end
end

% force the combined image color values to be between 0 and 255
combined_image = uint8( combined_image );

% display the combined tree_path.jpg and wolverine.jpg
figure, imshow( combined_image ); title( 'Weight Combined Image' );

% create a blank image the same size as tree_path.jpg
wolverine_restored_big_image = zeros( tree_path_y_size, tree_path_x_size, 3 );

% take the values in the combined image and subtract them from the original
% tree_path.jpg values, this will give the values that were added to
% tree_path.jpg above, then divide these values by WEIGHTED_COMBINE_VALUE in order to try 
% to get the original values in wolverine.jpg
for x_value = 1:tree_path_x_size
    for y_value = 1:tree_path_y_size
        wolverine_restored_big_image( y_value, x_value, 1 ) = ( combined_image( y_value, x_value, 1 ) - original_tree_path_image( y_value, x_value, 1 ) ) / WEIGHTED_COMBINE_VALUE;
        wolverine_restored_big_image( y_value, x_value, 2 ) = ( combined_image( y_value, x_value, 2 ) - original_tree_path_image( y_value, x_value, 2 ) ) / WEIGHTED_COMBINE_VALUE;
        wolverine_restored_big_image( y_value, x_value, 3 ) = ( combined_image( y_value, x_value, 3 ) - original_tree_path_image( y_value, x_value, 3 ) ) / WEIGHTED_COMBINE_VALUE;
    end
end

% force wolverine restored image color values to be between 0 and 255
wolverine_restored_big_image = uint8( wolverine_restored_big_image );

if DISPLAY_INTERMEDIATE_IMAGES
    
    % display the restored wolverine.jpg that is still the size of tree_path.jpg
    figure, imshow( wolverine_restored_big_image ); title( 'Restored Wolverine - Tree Path Size' );
end

% resize wolverine_restored_big_image to the size of the original wolverine.jpg
wolverine_restored_image = imresize( wolverine_restored_big_image, [ original_wolverine_y_size , original_wolverine_x_size ] );

% display the restored wolverine image that is the original wolverine.jpg size
figure, imshow( wolverine_restored_image ); title( 'Restored Wolverine - Original Size' );

% compute the Peak Signal-to-Noise Ratio (PSNR) between the original
% wolverine.jpg and the wolverine image restored from the combined image
% The bigger the PSNR the closer the two images are to being exactly the
% same and if the PSNR is infinity the images are exactly the same
% If not infinity values of 30 to 50 are very good and values above 50 are
% excellent/amazing
% Displayed in the Matlab command window
mean_square_error = sum( sum( sum( ( original_wolverine_image - wolverine_restored_image ).^2 ) ) ) / double( original_wolverine_x_size * original_wolverine_y_size * 3 );
disp(' ')
disp('The PSNR between the original wolverine.jpg and the restored wolverine taken from the combined image:')
PSNR = 10 * log10( ( 255 )^2 / mean_square_error )

% DISPLAY_TESTING_IMAGES =
% 0 => no extra tests
% 1 => if the combined image is resized
% 2 => if the combined image is stored as a heavily compressed .jpg
% 3 => if the combined image has added noise
% 4 => show all tests
if (DISPLAY_TESTING_IMAGES ~= 0) && (DISPLAY_TESTING_IMAGES < 5)

    % try to restore the wolverine image from the combined image when the 
    % combined image is resized
    if (DISPLAY_TESTING_IMAGES == 1) || (DISPLAY_TESTING_IMAGES == 4)
    
        % the percent to resize the combined image
        PERCENT_TO_RESIZE = 0.4;

        % resize the combined image
        resized_combined_image = imresize( combined_image, [ tree_path_y_size * PERCENT_TO_RESIZE, tree_path_x_size * PERCENT_TO_RESIZE ] );
        
        if DISPLAY_INTERMEDIATE_IMAGES
            
            % display the resized combined image
            figure, imshow( resized_combined_image ); title( 'Combine Image - Resized' );
        end
        
        % restore the resized combined image to its original size
        restored_combined_image = imresize( resized_combined_image, [tree_path_y_size, tree_path_x_size ] );

        if DISPLAY_INTERMEDIATE_IMAGES

            % display the combined image that has been returned to its
            % original size
            figure, imshow( restored_combined_image ); title( 'Combined Image - Resized to Original Size' );
        end
        
        % try to get the original values in wolverine.jpg
        for x_value = 1:tree_path_x_size
            for y_value = 1:tree_path_y_size
                wolverine_restored_big_image( y_value, x_value, 1 ) = ( restored_combined_image( y_value, x_value, 1 ) - original_tree_path_image( y_value, x_value, 1 ) ) / WEIGHTED_COMBINE_VALUE;
                wolverine_restored_big_image( y_value, x_value, 2 ) = ( restored_combined_image( y_value, x_value, 2 ) - original_tree_path_image( y_value, x_value, 2 ) ) / WEIGHTED_COMBINE_VALUE;
                wolverine_restored_big_image( y_value, x_value, 3 ) = ( restored_combined_image( y_value, x_value, 3 ) - original_tree_path_image( y_value, x_value, 3 ) ) / WEIGHTED_COMBINE_VALUE;
            end
        end