Error in using "Rand" function while embedding a watermark in an image.

I am a M.Tech student and I am pursuing my thesis work in Image Watermarking domain. I found a code over the internet and tried to implement it But I encountered an error while doing so. The error is with random function.

The error is as follows:-

*Error using rand*
*State must be a double scalar or the output of RAND('state').*

*Error in dwt_cdma_recover_section (line 15)*

*rand('state',key);*

*Error in cdma_dwt_watermark_section (line 54)*

*messageR = dwt_cdma_recover_section(watermarkR, message_imageR, key);*

I searched a lot about this error on the internet but could not find any appropriate solution.

The code is:-

if true
  % code

*%cdma_dwt_watermark_section.m*

%This is the image we want to watermark

original_image = 'lena_color.bmp';

%This is the image we want to embed in the watermark

message_image = 'testmessage.bmp';

message_image_sections = double(imread(message_image));

[Mx My] = size(message_image_sections);

%This is for embeding messages in RGB spectrum

message_imageR = message_image_sections(:, 1:(My*(1/3)));

message_imageG = message_image_sections(:, (My*(1/3)):(My*(2/3)));

message_imageB = message_image_sections(:, (My*(2/3)):My);

%This is the key that will be used with both the encrypter and decrypter

key = 'key_working.bmp';

figure

imshow(key);

%This is the name of the output watermark image

watermarked_name = 'watermarked_image.bmp';

%This is used to set the gain

k = 2;

%Set to 1 to test RGB watermark encoding

color = 1;

% Read in image

file_name = original_image;

image_object=double(imread(file_name));

%Display UnWatermarked Image

figure

imshow(original_image);

title('Original Image');

%Used for testing

if color == 1

%Seperate the image to its RGB

image_objectR = image_object(:, :, 1);

image_objectG = image_object(:, :, 2);

image_objectB = image_object(:, :, 3);

%Run the watermark embed on each spectrum

watermarkR = dwt_cdma_embed_section(image_objectR, message_imageR, key, k);
watermarkG = dwt_cdma_embed_section(image_objectG, message_imageG, key, k);

watermarkB = dwt_cdma_embed_section(image_objectB, message_imageB, key, k);

%Combine the individual watermarked RGB into one image

watermark(:, :, 1) = watermarkR;

watermark(:, :, 2) = watermarkG;

watermark(:, :, 3) = watermarkB;

%Display the final watermarked image
figure

imshow(watermark, []);

title('Watermarked Image Color');

imwrite(watermark, watermarked_name,'bmp');

%Recover the Watermark message from the Red

messageR = dwt_cdma_recover_section(watermarkR, message_imageR, key);

figure
imshow(messageR, []);

title('Hidden Message Red');

%Recover the Watermark message from the Green

messageG = dwt_cdma_recover_section(watermarkG, message_imageG, key);
figure

imshow(messageG, []);

title('Hidden Message Green');

%Recover the Watermark message from the Blue

messageB = dwt_cdma_recover_section(watermarkB, message_imageB, key);

figure

imshow(messageB, []);

title('Hidden Message Blue');

message_full(:, 1:(My*(1/3))) = messageR;

message_full(:, (My*(1/3)):(My*(2/3))) = messageG;

message_full(:, (My*(2/3)):My) = messageB;

figure

imshow(message_full, []);

title('Rebuilt Hidden Message');

else

%Embed Message into Watermarked Image

watermark = dwt_cdma_embed(image_object, message_image, key, k);

figure

imshow(watermark, []);

title('Watermarked Image');

message = dwt_cdma_recover(watermark, message_image, key);

figure

imshow(message, []);

title('Hidden Message');

imwrite(watermark, watermarked_name,'bmp');

end

*%dwt_cdma_recover_section.m*

function [message] = dwt_cdma_recover_section(watermarked_image, message_image, key_image)

%clear all;

thresh = 0.5; % used for testing threshold

% determine size of watermarked image

[Mw Nw] = size(watermarked_image);

% read in the message

orig_watermark = message_image;

% determine size of original watermark

[Mo No] = size(orig_watermark);

% read in key for PN generator

key=double(imread(key_image))./256;

% reset MATLAB's PN generator to state "key"

rand('state',key);

% initalize message to all ones

message_vector=ones(1,Mo*No);

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

correlation_h = zeros(message_vector);

correlation_v = zeros(message_vector);

correlation = zeros(message_vector);

% add pn sequences to HL and LH componants when message = 0

for kk=1:length(message_vector)

pn_sequence_h=round(2*(rand(Mw/2,Nw/2)-thresh));

pn_sequence_v=round(2*(rand(Mw/2,Nw/2)-thresh));

correlation_h(kk)=corr2(HL,pn_sequence_h);

correlation_v(kk)=corr2(LH,pn_sequence_v);

correlation(kk)=(correlation_h(kk)+correlation_v(kk))/2;

end

for kk=1:length(message_vector)

if (correlation(kk) > mean(correlation))

message_vector(kk)=0;

end

end

message=reshape(message_vector,Mo,No);

return

Key (key_working2.bmp)

key =
0.8242

0.5391

0.7813

0.5625

0.5586

0.2734

0.2773

0.4805

0.6250

0.5391

0.4648

0.5859

0.4375

0.5508

0.4297

0.4648

0.4414

0.5273

0.5234

0.3398

0.7344

0.6836

0.4063

0.6875

0.3594

0.8555

0.4688

0.3594

0.0430

0.5820

0.6133

0.5547

0.5156

0.8711

0.6719

I have written only the functions which are giving error. this is not the complete code.

Please help me.

[Walter Roberson]

Are you intending that "key" be itself the string of bits to use for the key, or are you intending that "key" be the filename of an image that has bits to use for the key?

Your code attempts to use the entire content of the image stored in the key_image (whose variable is called "key" in the calling context), but you cannot use an entire image array as the key for rand().

In order to figure out what you probably want, we would need to see the code that did the embedding.

[ddd hhh]

Sir I have mailed you the code.

[ddd hhh]

Sir the embedding code is as follows:-

if true

%This is the image we want to watermark

original_image = 'lena_color.bmp';

%This is the image we want to embed in the watermark

message_image = 'testmessage.bmp';

message_image_sections = double(imread(message_image));

[Mx My] = size(message_image_sections);

%This is for embeding messages in RGB spectrum

message_imageR = message_image_sections(:, 1:(My*(1/3)));

message_imageG = message_image_sections(:, (My*(1/3)):(My*(2/3)));

message_imageB = message_image_sections(:, (My*(2/3)):My);

%This is the key that will be used with both the encrypter and decrypter

key = 'key_working2.bmp';

%This is the name of the output watermark image

watermarked_name = 'watermarked_image.bmp';

%This is used to set the gain

k = 2;

%Set to 1 to test RGB watermark encoding

color = 1;

% Read in image

file_name = original_image;

image_object=double(imread(file_name));

%Display UnWatermarked Image

figure

imshow(original_image);

title('Original Image');

%Used for testing

if color == 1

%Seperate the image to its RGB

image_objectR = image_object(:, :, 1);

image_objectG = image_object(:, :, 2);

image_objectB = image_object(:, :, 3);

%Run the watermark embed on each spectrum

watermarkR = dwt_cdma_embed_section(image_objectR, message_imageR, key, k);

watermarkG = dwt_cdma_embed_section(image_objectG, message_imageG, key, k);

watermarkB = dwt_cdma_embed_section(image_objectB, message_imageB, key, k);

%Combine the individual watermarked RGB into one image

watermark(:, :, 1) = watermarkR;

watermark(:, :, 2) = watermarkG;

watermark(:, :, 3) = watermarkB;

%Display the final watermarked image

figure

imshow(watermark, []);

title('Watermarked Image Color');

imwrite(watermark, watermarked_name,'bmp');

%Recover the Watermark message from the Red

messageR = dwt_cdma_recover_section(watermarkR, message_imageR, key);

figure

imshow(messageR, []);

title('Hidden Message Red');

%Recover the Watermark message from the Green

messageG = dwt_cdma_recover_section(watermarkG, message_imageG, key);

figure

imshow(messageG, []);

title('Hidden Message Green');

%Recover the Watermark message from the Blue

messageB = dwt_cdma_recover_section(watermarkB, message_imageB, key);

figure

imshow(messageB, []);

title('Hidden Message Blue');

message_full(:, 1:(My*(1/3))) = messageR;

message_full(:, (My*(1/3)):(My*(2/3))) = messageG;

message_full(:, (My*(2/3)):My) = messageB;

figure

imshow(message_full, []);

title('Rebuilt Hidden Message');

else

%Embed Message into Watermarked Image

watermark = dwt_cdma_embed(image_object, message_image, key, k);

figure

imshow(watermark, []);

title('Watermarked Image');

message = dwt_cdma_recover(watermark, message_image, key);

figure

imshow(message, []);

title('Hidden Message');

imwrite(watermark, watermarked_name,'bmp');

end end

dwt_cdma_embed.m

if true
function [watermarked] = dwt_cdma_embed(image_object, message_image, key_image, k)
thresh = 0.5; %Used for testing threshold
% determine size of watermarked image
[Mw Nw]=size(image_object);
% read in the message image
file_name= message_image;
message=double(imread(file_name));
[Mm Nm] = size(message);
message_vector=round(reshape(message,Mm*Nm,1)./256);
% read in key for PN generator
%key = imread(key_image);
key=double(imread(key_image))./256;
% reset MATLAB's PN generator to state "key"
rand('state',key);
[LL,HL,LH,HH] = dwt2(image_object,'haar');
%[LL,HL,LH,HH] = dwt2(cover_object, 'db1');
% add pn sequences to HL and LH componants when message = 0
for kk=1:length(message_vector)
pn_sequence_h=round(2*(rand(Mw/2,Mw/2)-thresh));
pn_sequence_v=round(2*(rand(Mw/2,Mw/2)-thresh));
if (message(kk) == 0)
HL=HL+k*pn_sequence_h;
LH=LH+k*pn_sequence_v;
end
end
% perform IDWT
watermarked_image = idwt2(LL,HL,LH,HH,'haar',[Mw,Nw]);
% convert back to uint8
watermarked_image_uint8=uint8(watermarked_image);
watermarked = watermarked_image_uint8;
return
end

dwt_cdma_embed_section.m

if true
function [watermarked] = dwt_cdma_embed_section(image_object, message_image, key_image, k)
thresh = 0.5; %used for testing of different thresholds
% determine size of watermarked image
[Mw Nw]=size(image_object);
% read in the message image
message = message_image;
[Mm Nm] = size(message);
message_vector=round(reshape(message,Mm*Nm,1)./256);
% read in key for PN generator
%key = imread(key_image);
key=double(imread(key_image))./256;
% reset MATLAB's PN generator to state "key"
rand('state',key);
[LL,HL,LH,HH] = dwt2(image_object,'haar');
%[LL,HL,LH,HH] = dwt2(cover_object, 'db1');
% add pn sequences to HL and LH componants when message = 0
for kk=1:length(message_vector)
pn_sequence_h=round(2*(rand(Mw/2,Mw/2)-thresh));
pn_sequence_v=round(2*(rand(Mw/2,Mw/2)-thresh));
if (message(kk) == 0)
HL=HL+k*pn_sequence_h;
LH=LH+k*pn_sequence_v;
end
end
% perform IDWT
watermarked_image = idwt2(LL,HL,LH,HH,'haar',[Mw,Nw]);
% convert back to uint8
watermarked_image_uint8=uint8(watermarked_image);
watermarked = watermarked_image_uint8;
return
end