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From: mohammad on 19 May 2010 10:04
%Name: Chris Shoemaker
%Course: EER-280 - Digital Watermarking
%Project: Block DCT Based method, using comparision between mid-band coeffcients
% Watermark Embeding

clear all;

% save start time
start_time=cputime;

k=50; % set minimum coeff difference
blocksize=8; % set the size of the block in cover to be used for each bit in watermark

% read in the cover object
file_name='_lena_std_bw.bmp';
cover_object=double(imread(file_name));

% determine size of cover image
Mc=size(cover_object,1); %Height
Nc=size(cover_object,2); %Width

% determine maximum message size based on cover object, and blocksize
max_message=Mc*Nc/(blocksize^2);

% read in the message image
file_name='_copyright.bmp';
message=double(imread(file_name));
Mm=size(message,1); %Height
Nm=size(message,2); %Width

% reshape the message to a vector
message=round(reshape(message,Mm*Nm,1)./256);

% check that the message isn't too large for cover
if (length(message) > max_message)
error('Message too large to fit in Cover Object')
end

% pad the message out to the maximum message size with ones
message_pad=ones(1,max_message);
message_pad(1:length(message))=message;

% generate shell of watermarked image
watermarked_image=cover_object;

% process the image in blocks
% encodes such that (5,2) > (4,3) when message(kk)=0
% and that (5,2) < (4,3) when message(kk)=1
x=1;
y=1;
for (kk = 1:length(message_pad))

% transform block using DCT
dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1));

% if message bit is black, (5,2) > (4,3)
if (message_pad(kk) == 0)

% if (5,2) < (4,3) then we need to swap them
if (dct_block(5,2) < dct_block(4,3))
temp=dct_block(4,3);
dct_block(4,3)=dct_block(5,2);
dct_block(5,2)=temp;
end

% if message bit is white, (5,2) < (4,3)
elseif (message_pad(kk) == 1)

% if (5,2) > (4,3) then we need to swap them
if (dct_block(5,2) >= dct_block(4,3))
temp=dct_block(4,3);
dct_block(4,3)=dct_block(5,2);
dct_block(5,2)=temp;
end
end

% now we adjust the two values such that their difference >= k
if dct_block(5,2) > dct_block(4,3)
if dct_block(5,2) - dct_block(4,3) < k
dct_block(5,2)=dct_block(5,2)+(k/2);
dct_block(4,3)=dct_block(4,3)-(k/2);
end
else
if dct_block(4,3) - dct_block(5,2) < k
dct_block(4,3)=dct_block(4,3)+(k/2);
dct_block(5,2)=dct_block(5,2)-(k/2);
end
end

% transform block back into spatial domain
watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=idct2(dct_block);

% move on to next block. At and of row move to next row
if (x+blocksize) >= Nc
x=1;
y=y+blocksize;
else
x=x+blocksize;
end
end

% convert to uint8 and write the watermarked image out to a file
watermarked_image_int=uint8(watermarked_image);
imwrite(watermarked_image_int,'dct1_watermarked.bmp','bmp');

% display processing time
elapsed_time=cputime-start_time,

% display psnr of watermarked image
psnr=psnr(cover_object,watermarked_image,Nc,Mc),

% display watermarked image
figure(1);
imshow(watermarked_image,[])
title('Watermarked Image')





this is the code ,i tried searching author but no luck...
From: Walter Roberson on 19 May 2010 10:31
mohammad wrote:
> %Name: Chris Shoemaker
> %Course: EER-280 - Digital Watermarking
> %Project: Block DCT Based method, using comparision between mid-band
> coeffcients
> % Watermark Embeding

> this is the code ,i tried searching author but no luck...

Did you try his web page http://www.vu.union.edu/~shoemakc/

From: Walter Roberson on 19 May 2010 10:43
mohammad wrote:
> Walter Roberson <roberson(a)hushmail.com> wrote in message
> <hsv3h9$noa$1(a)canopus.cc.umanitoba.ca>...
>> mohammad wrote:
>> > i have a code dct1_embed which i got it here itself, it watermarks
>> an > image but converts it to grey scale.
>> > > what i need is that the image should not be converted to grey
>> scale , > can anybody help me out with this topic..

>> You could watermark the three planes separately, I suppose. [...]

> can you make changes to existing code ,so that it works...

Assignments are given to you so that you will learn the techniques. If I
do the work for you, I do not see any learning benefit for you.
From: mohammad on 19 May 2010 14:41
Walter Roberson <roberson(a)hushmail.com> wrote in message <WNSIn.11146$7d5.10402(a)newsfe17.iad>...
> mohammad wrote:
> > Walter Roberson <roberson(a)hushmail.com> wrote in message
> > <hsv3h9$noa$1(a)canopus.cc.umanitoba.ca>...
> >> mohammad wrote:
> >> > i have a code dct1_embed which i got it here itself, it watermarks
> >> an > image but converts it to grey scale.
> >> > > what i need is that the image should not be converted to grey
> >> scale , > can anybody help me out with this topic..
>
> >> You could watermark the three planes separately, I suppose. [...]
>
> > can you make changes to existing code ,so that it works...
>
> Assignments are given to you so that you will learn the techniques. If I
> do the work for you, I do not see any learning benefit for you.


After i tried what i could do ,then only i am asking for help....
its a part of final sem project thats why was looking for quick reply dont want to mess with my grades ,u guys know indian education system....
From: mohammad on 19 May 2010 14:45
Walter Roberson <roberson(a)hushmail.com> wrote in message <VCSIn.16177$TL5.3940(a)newsfe24.iad>...
> mohammad wrote:
> > %Name: Chris Shoemaker
> > %Course: EER-280 - Digital Watermarking
> > %Project: Block DCT Based method, using comparision between mid-band
> > coeffcients
> > % Watermark Embeding
>
> > this is the code ,i tried searching author but no luck...
>
> Did you try his web page http://www.vu.union.edu/~shoemakc/


this page contains nothing relevant to the project....
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