how to extract the watermark after decryption. please help I am getting an error in watermark extraction steps. Thank you in advance

clc;

close all;

clear all;

imageinput=imread('lena.jpg');

imageinput=imresize(imageinput,[256,256]);

imageinput=rgb2gray(imageinput);

figure(1);imshow(imageinput);title('original Host image');

%P=im2double(imageinput);

[F1,F2]= wfilters('haar', 'd');

[LL,LH,HL,HH] = dwt2(imageinput,'haar','d');

[U1,S1,V1]= svd(LL);

S1_temp=S1;

imw2=imread('deblur.jpg');

imw2=imresize(imw2,[128 128]);

imw2=rgb2gray(imw2);

figure(2);imshow(imw2);title('watermark image');

%watermark=im2double(imw2);

[WF1,WF2]= wfilters('haar', 'd');

[L_L,L_H,H_L,H_H] = dwt2(imw2,'haar','d');

[U2,S2,V2]= svd(L_L);

[x y]=size(S2);

alfa= input('Insert the alfa Value = ');

for i=1:x

for j=1:y

S1(i,j) =S1(i,j) + alfa * S2(i,j);

end

end

wimg = U1*S1*V1';

Watermarkedimage=wimg;

%computing level-1 idwt2

Watermarkedimage_final_pre= idwt2(Watermarkedimage,LH,HL,HH,'haar');

Watermarkedimage_final=uint8(Watermarkedimage_final_pre);

figure(3);imshow(Watermarkedimage_final,[]), title('final Watermarkedimage ')

%3D chaotic map for image encryption

%3.53<l<3.81

%0<b<0.022

%0<a<0.015

% x(i+1)=l*x(i)*(1-x(i))+b*y(i)*y(i)*x(i)+a*z(i)*z(i)*z(i);

% y(i+1)=l*y(i)*(1-y(i))+b*z(i)*z(i)*y(i)+a*x(i)*x(i)*x(i);

% z(i+1)=l*z(i)*(1-z(i))+b*x(i)*x(i)*z(i)+a*y(i)*y(i);

%modify the chaos by this equation furthure

%z(i+1)=l*z(i)*(1-z(i))+b*x(i)*x(i)*z(i)+a*y(i)*y(i)*y(i);

%initial conditions

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%% 3D CHAOS GENERATION CODE%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

x(1)=0.2350;

y(1)=0.3500;

z(1)=0.7350;

a(1)=0.0125;

b(1)=0.0157;

l(1)=3.7700;

image_height=256;

for i=1:1:70000

x(i+1)=l*x(i)*(1-x(i))+b*y(i)*y(i)*x(i)+a*z(i)*z(i)*z(i);

y(i+1)=l*y(i)*(1-y(i))+b*z(i)*z(i)*y(i)+a*x(i)*x(i)*x(i);

z(i+1)=l*z(i)*(1-z(i))+b*x(i)*x(i)*z(i)+a*y(i)*y(i);

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%histogram equalization and preparation for use%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

x=ceil(mod((x*100000),image_height));

y=ceil(mod((y*100000),image_height));

z=ceil(mod((z*100000),image_height));

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%IMAGE INPUT%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

original=Watermarkedimage_final;

rgb=original;

[row,col]=size(rgb);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%INITIALIZE THE VALUE OF ROTATION%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

n=500;

p=600;

q=700;

for j=1:1:row

k(j)=x(j+n);

l(j)=y(j+p);

end

% for i=1:1:row

% k(i)=x(i+n);

% end

% for j=1:1:col

% l(j)=y(j+p);

% end

for j=1:1:col*row

m(j)=z(j+q);

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% IF k is even right shift row else left shift row%%%%%%%%%%%%%%%%%

% If l is even shift up column else down shift column%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%ROTATION OPERATION%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for i=1:1:row

for j=1:1:col

if(mod(k(i),2)==0)

if((j+k(i))<=col) %shift right of row

sh_row(i,j+k(i))=rgb(i,j);

row_shift_even(i,j)=j+k(i);

else

sh_row(i,(j+k(i)-col))=rgb(i,j);

row_shift_even(i,j)=(j+k(i)-col);

end

else

if((j-k(i))>=1) %shift left of row

sh_row(i,j-k(i))=rgb(i,j);

row_shift_odd(i,j)=j-k(i);

else

sh_row(i,(col+j-k(i)))=rgb(i,j);

row_shift_odd(i,j)=col+j-k(i);

end

end

end

end

for j=1:1:col

for i=1:1:row

if(mod(l(j),2)==0)

if((i-l(j))>=1) %shift up of column

sh_col(i-l(j),j)=sh_row(i,j);

col_shift_even(i,j)=i-l(j);

else

sh_col((row+i-l(j)),j)=sh_row(i,j);

col_shift_even(i,j)=row+i-l(j);

end

else

if((i+l(j))<=row) %shift down of column

sh_col(i+l(j),j)=sh_row(i,j);

col_shift_odd(i,j)=i+l(j);

else

sh_col((i+l(j)-row),j)=sh_row(i,j);

col_shift_odd(i,j)=(i+l(j)-row);

end

end

end

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%XOR IMAGE%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

total_length=row*col;

column_image=reshape(sh_col,1,total_length);

for i=1:1:total_length

xorr1(1,i)=bitxor(column_image(i),m(j));

end

y=reshape(xorr1,row,col);

imwrite(y, 'encypted_peppers.jpg', 'Quality', 100);

figure

subplot(3,2,1)

imshow(rgb)

title('Original Image');

subplot(3,2,2)

imhist(rgb)

title('Histogram of original Image');

subplot(3,2,3)

imshow(y)

title('Encrypted Image');

subplot(3,2,4)

imhist(y)

title('Histogram of Encrypted Image');

[row,col]=size(y);

rgb=y;

total_length=row*col;

column_image=reshape(rgb,1,total_length);

for i=1:1:total_length

xorr1(1,i)=bitxor(column_image(i),m(j));

end

shuffled_image=reshape(xorr1,row,col);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% IF k is even right shift row else left shift row%%%%%%%%%%%%%%%%%

% If l is even shift up column else down shift column%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%ROTATION OPERATION%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%ROW SHIFTING%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for j=1:1:col

for i=1:1:row

if(mod(l(j),2)==0)

if((i+l(j))<=row) %shift down of column

sh_col(i+l(j),j)=shuffled_image(i,j);

col_shift_even(i,j)=i+l(j);

else

sh_col((i+l(j)-row),j)=shuffled_image(i,j);

col_shift_even(i,j)=(i+l(j)-row);

end

else

if((i-l(j))>=1) %shift up of column

sh_col(i-l(j),j)=shuffled_image(i,j);

col_shift_odd(i,j)=i-l(j);

else

sh_col((row+i-l(j)),j)=shuffled_image(i,j);

col_shift_odd(i,j)=row+i-l(j);

end

end

end

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for i=1:1:row

for j=1:1:col

if(mod(k(i),2)==0)

if((j-k(i))>=1) %shift left of row

sh_row(i,j-k(i))=sh_col(i,j);

row_shift_even(i,j)=j-k(i);

else

sh_row(i,(col+j-k(i)))=sh_col(i,j);

row_shift_even(i,j)=col+j-k(i);

end

else

if((j+k(i))<=col) %shift right of row

sh_row(i,j+k(i))=sh_col(i,j);

row_shift_even(i,j)=j+k(i);

else

sh_row(i,(j+k(i)-col))=sh_col(i,j);

row_shift_even(i,j)=(j+k(i)-col);

end

end

end

end

subplot(3,2,5)

imshow (sh_row)

title('decrypted image');

subplot(3,2,6)

imhist(sh_row)

title('histogram decrypted image');

imwrite(sh_row, 'Decrypted image.jpg', 'Quality', 100);

[F11,F22]= wfilters('haar', 'd');

[a b c d]=dwt2(sh_row,'haar','d');

[U3,S3,V3]= svd(a);

for i=1:x

for j=1:y

recov_image(i,j)=(S3(i,j)-S1_temp(i,j))/alfa;

end

end

ewatr = U2*recov_image*V2';

recovered_image=ewatr;

recovered_image_final=idwt2(recovered_image,L_H,H_L,H_H,'haar');

recovered_image_final=uint8(recovered_image_final);

figure(5);imshow(recovered_image_final);

title('extracted watermark')

[DGM]

I can't run this since I don't have Wavelet Toolbox, so there's that.

Is there any reason to believe that this will survive lossy compression anyway? Saving with Q = 100% isn't lossless. It's still downsampled.

[Suniti Singh]

Thank you for your response sir.. but I am working on this in matlab when I do only watermarking and extraction it works perfectly but when I introduced encryption and decryption in between the extraction algorithm doesn't work. It gives an error as colon doesn't support an scaler.

[DGM]

What is the actual, whole error message?

[Suniti Singh]

sir i am getting the error as below:

Colon operands must be real scalars.

Error in Untitled (line 247)

for j=1:y

Answer 1

[Walter Roberson]

 for i=1:1:70000
     x(i+1)=l*x(i)*(1-x(i))+b*y(i)*y(i)*x(i)+a*z(i)*z(i)*z(i);
     y(i+1)=l*y(i)*(1-y(i))+b*z(i)*z(i)*y(i)+a*x(i)*x(i)*x(i);

x and y are long vectors

 x=ceil(mod((x*100000),image_height));
 y=ceil(mod((y*100000),image_height));

vector operations so x and y are still vectors after. The values are integers.

y=reshape(xorr1,row,col);

y is now a 2d image not related to its previous value

for i=1:x
  for j=1:y

x is still a vector of integers, and matlab treats the first as 1:x(1). But y is a 2d array of non-integers

Perhaps you wanted to iterate over rows and columns?

[Suniti Singh]

Actually after decryption I want to extract the watermark from marked image at receiver end but getting this error.