spread spectrum watermarking - error in the code

i have written a code for spread spectrum watermarking. But it shows the error that input must be a string. can any one help me to correct the program.

clc;
clear all;
close all;
 k=.0002;            % set the gain factor for embeding
 % read in the cover object
cover_object=dicomread('189.dcm');
cover_object = uint8(255*mat2gray(cover_object));
figure, imshow(cover_object,[])
 title('input Image')

    % determine size of watermarked image
  [Mc Nc]=size(cover_object);   

   %reading the watermark image
  fid=fileread('try.txt');
  data=uint8(fid);
  data_b=dec2bin(data);
  data_f=reshape(data_b',1,[])

message_vector=data_f;
 x=length(message_vector);
 els = {'p',[-0.125 0.125],0};

lshaarInt = liftwave('haar','int2int');
lsnewInt = addlift(lshaarInt,els);

[LL,LH,HL,HH] = lwt2(double(cover_object),lsnewInt);
[LL1,LH1,HL1,HH1] = lwt2(double(LL),lsnewInt);
 figure,imshow(LL,[]);
 title('LL band');

figure,imshow(LL1,[]);
title(' LL1 band');
 w=0;
 [m n]=size(LL1);
pn=zeros(x,m*n);
 % add pn sequences to HH 
for kk=1:x
     pn_sequence_h=round(rand(1,m*n));
     pn(kk,:)=pn_sequence_h;
         if (message_vector(kk) == 1)
             w=w+pn_sequence_h;

       end
  end
   host_vector=LL1(:);
    Iw=host_vector+k*w';
   wm=buffer(Iw,n);
    figure, imshow(wm,[])
   title(' band after watermarking')
     % perform IDWT
  LL =  uint8(ilwt2(wm,LH1,HL1,HH1,lsnewInt));
  watermarked_image=uint8(ilwt2(double(LL),LH,HL,HH,lsnewInt));

    % convert back to uint8
   watermarked_image_uint8=uint8(watermarked_image);

   % display watermarked image
   figure,imshow(watermarked_image_uint8,[])

   % extraction part

    title('Watermarked Image')
     els = {'p',[-0.125 0.125],0};
  % 
   lshaarInt = liftwave('haar','int2int');
   lsnewInt = addlift(lshaarInt,els);

   [LL,LH,HL,HH] = lwt2(double(watermarked_image_uint8),lsnewInt);
   [LL1,LH1,HL1,HH1] = lwt2(double(LL),lsnewInt);
  messagevector=[];

     iw=LL1(:);
     for kk=1:x
         if (sign(cov(iw',pn(kk,:))) < 0)
           messagevector(kk)=0;
       else
                    messagevector(kk)=1;

       end
    end

e=reshape(messagevector,7,[]);
r=bin2dec(e');
ans=char(r)'
fido=fopen('out1.txt','w');
fwrite(fido,ans);
fclose(fido);

   processed=double(watermarked_image);
  original=double(cover_object);
  [m n]=size(original);
  %mserror
  error=original-processed;
  se=error.*error;
  sumse=sum(sum(se));
  mse=sumse/(m*n);
  %mserror

ma=max(max(original));
t=10*log10(ma*ma/mse);
 display 'The PSNR is :',t 

[ssimval,b] = SSIM(watermarked_image,cover_object);
 display 'The ssim is :',ssimval        

   [ssim,b] = SSIM(message,watermark);
   display 'The ssim of watermark is :',ssimval

[Walter Roberson]

As you did not provide the .dcm file or the .txt file for us to test with, do we at least get a hint as to which line the error was reported for? Maybe even a complete copy of the error message?

[uthara ravi]

sorry i will attach the files u asked for.dcm file is adicom image that i dowloaded from matworks itself(dicom sample images) thank u for your time and consideration.

Answer 1

[Walter Roberson]

dec2bin() does not return an array that has 0 and 1 in each element. dec2bin() returns an array that has '0' and '1' in it, the characters for printing 0 and 1 rather than the values 0 and 1.

You are manipulating the '0' and '1' values believing that they are numeric 0 and 1. You are getting a numeric vector e as your result. You are then trying to convert that numeric vector to decimal as if it were suitable input for bin2dec, but bin2dec needs '0' and '1'.

Solution:

    data_b = dec2bin(data) - '0';

Now the result will be numeric 0 and numeric 1.

Then later,

r = bin2dec( char(e' + '0'));

This converts the numeric 0 and numeric 1 to '0' and '1'

[uthara ravi]

Thank you sir. let me try this suggestion