i am finding an error when i am executing the following code. kindly help me out?

error in 91 line.

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

[Walter Roberson]

Please show the complete error message.

[chaitanya g p]

??? Error: File: dwt_svd.m Line: 91 Column: 11 Expression or statement is incorrect--possibly unbalanced (, {, or [.

Answer 1

[Jan]

Please read the message. It tells you the exact line (while we can only guess which is the line 91) and even the character, which is the problem: There is a parenthesis, brace or bracket, which is closed before another one was opened. I assume, this problem should be easy to fix.

Perhaps this is the offending line:

[~, ~, recon_sig_corr, LL4, HH4] = ...

If you use an older Matlab version <=R2009a, the "~" are not allowed. Replace this by:

[dummy, dummy, recon_sig_corr, LL4, HH4] = ...

If this is the problem, if appears in the line "[~, watermark_wrong, recon_sig_wrng, LL4wr, HH4wr] = ..." also.

PS. A clear all on the top of a function is a waste of time, energy and power. There is simply no reason for a brutal clearing of an empty workspace.

[chaitanya g p]

the following function call is happening where the error message is being shown.

    [~, ~, recon_sig_corr, LL4, HH4] = ...
            watermark_extraction(watermarked_image, watermark_logo, key, ...
            print_figures, true);

[chaitanya g p]

yes. changing "~" to "dummy" worked. but it gave rise to a few more errors in the associate function files.

[chaitanya g p]

??? Undefined function or method 'decimalToBinaryVector' for input arguments of type 'double'.

Error in ==> signature_embedding at 51 binary_coefficients{p} = decimalToBinaryVector(integer_part(p), 16);

if true

      %%Signature embedding algorithm
     function LL_inv = signature_embedding(LL, signature, print_figures)

     % 1. Using Haar wavelet, further decompose LL band to the 4th level.
     [LL_1, HL_1, LH_1, HH_1] = dwt2(LL, 'haar');    % 1st step DWT
     [LL_2, HL_2, LH_2, HH_2] = dwt2(LL_1, 'haar');  % 2nd step DWT
     [LL_3, HL_3, LH_3, HH_3] = dwt2(LL_2, 'haar');  % 3rd step DWT
     [LL_4, HL_4, LH_4, HH_4] = dwt2(LL_3, 'haar');  % 4rth step DWT

     if (print_figures == true)
         % Images coding.
         cod_cA = wcodemat(LL_4);
         cod_cH = wcodemat(HL_4);
         cod_cV = wcodemat(LH_4);
         cod_cD = wcodemat(HH_4);
         dec2dim = [cod_cA, cod_cH; cod_cV, cod_cD];

         % Plot 4-th step decomposition
         figure;
         image(dec2dim);
         title('4-th step DWT decomposition');

         clear('dec2dim', 'cod_cA', 'cod_cH', 'cod_cV', 'cod_cD');
     end

     % 1. choose all in total 512 coefficients from LL_4 & HH_4
     % reshape them to row vectors of size 1x256
     LL_4 = reshape(LL_4, 1, length(LL_4)^2);
     HH_4 = reshape(HH_4, 1, length(HH_4)^2);

     % concatenate the above row vectors into a larger row vector of size 1x512
     combined_LL4_and_HH4_coef = [LL_4 HH_4];

     % keep record of the index position of negatives to put back the  sign in
     % inverse process
     negative_idxs =      combined_LL4_and_HH4_coef(logical(combined_LL4_and_HH4_coef)) < 0;

     % keep only the positive integer parts
     % combined_LL4_and_HH4_coeff_posint = round( abs( combined_LL4_and_HH4_coef ) );

     % separate the integer from the decimal fraction
     combined_LL4_and_HH4_coeff_pos = abs(combined_LL4_and_HH4_coef);
     integer_part = fix(combined_LL4_and_HH4_coeff_pos);
     fraction_part = abs(combined_LL4_and_HH4_coeff_pos - integer_part);

     % Convert the integer part into the binary code of L=16 bits.
binary_coefficients = {};
     for p = 1:length(integer_part)
         % binary_coefficients{p} = bitget( uint16( integer_part(p) ), 16:-1:1 );
         binary_coefficients{p} = decimalToBinaryVector(integer_part(p), 16);
     end

     % 2. Replace the n-th bit (10th bit) position of the coefficient with
     % signature bit
     for m = 1:length(signature)
         for n = 1:16
             if (n == 10)
                 binary_coefficients{1, m}(n) = signature(m);
             end
         end
     end
     % and then convert the binary code to its decimal representation
     bin2decimal = zeros(1, length(binary_coefficients));
     for x = 1:length(binary_coefficients)
         bin2decimal(x) = binaryVectorToDecimal(double(binary_coefficients{1, x}));
     end

     % reconstruct orignal array from integer and decimal fraction parts
     % cmb_coef = integer_part + fraction_part;
     bin2decimal = bin2decimal + fraction_part;

     % put back the negative signs
     bin2decimal(find(negative_idxs == 1)) = -     bin2decimal(find(negative_idxs == 1));

     % Clear workspace
     clear('LL_1', 'LL_2', 'LL_3', 'LL_4', 'HH_4', 'combined_LL4_and_HH4_coef',...
    'negative_idxs', 'combined_LL4_and_HH4_coeff_pos', 'integer_part',...
    'fraction_part', 'binary_coefficients', 'signature');

     % reshape the modified LL_4 & HH_4 sub-bands to their original size 16x16
     % each
     LL_4_modified = bin2decimal(1:256);
     HH_4_modified = bin2decimal(257:end);
     LL_4_modified = reshape(LL_4_modified, 16, 16);
     HH_4_modified = reshape(HH_4_modified, 16, 16);

     % Clear workspace
     clear('bin2decimal');

     % 3. Apply the inverse DWT with modified LL4 and HH4 band coefficients.
     LL_3_inv = idwt2(LL_4_modified, HL_4, LH_4, HH_4_modified, 'haar');
     LL_2_inv = idwt2(LL_3_inv, HL_3, LH_3, HH_3, 'haar');
     LL_1_inv = idwt2(LL_2_inv, HL_2, LH_2, HH_2, 'haar');
     LL_inv   = idwt2(LL_1_inv, HL_1, LH_1, HH_1, 'haar');

     % Clear workspace
     clear('LL_1_inv', 'LL_2_inv', 'LL_3_inv', 'LL_4_modified', ...
    'HL_1', 'HL_2', 'HL_3', 'HL_4', ...
    'LH_1', 'LH_2', 'LH_3', 'LH_4', ...
    'HH_1', 'HH_2', 'HH_3', 'HH_4_modified');

     end
end

 binary_coefficients{p} = decimalToBinaryVector(integer_part(p), 16); error here

[Jan]

The error "??? Undefined function or method 'decimalToBinaryVector'" means, that you do not have this function in your Matlab path. When such a message appears, asking an internet search engine is a good idea. This reveals, that this function belongs to the Data Acquisition Toolbox: http://www.mathworks.com/help/daq/ref/decimaltobinaryvector.html . Do you have this toolbox? You can write this function by your own easily. Look at dec2bin and omit the final conversion to a char.