Hiding text message in an image [MATLAB Code]

This code hides your secret message into an image [steganography]. Copy the below code and execute in your matlab.

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function []=txthide(arg)

% TXTHIDE  Hides text message (MSG) within an image, using a key (KEY).

% After typing txthide at the command line, a GUI appears that will guide

% the user through the process of encoding the text.  The maximum length of

% text that can be encoded is 1000 characters.  This could be

% modified, but represents a good comprimise between speed and

% functionality on the author's computer.

% Text can be hidden in a bitmap (*.bmp), a tif (*.tif) or a jpg (*.jpg ).

% However, the encoded image can only be saved as a bitmap or

% tif; the jpg format uses compression and the decoder will not return the

% correct MSG if the user tries to save the encoded image in this

% format.

% Any character from a common keyboard can be encoded, including the

% shifted characters and numbers, such as !@#$%^&*()_+123 etc.

%-----------------------------USER NOTES-------------------------------%

% 1.  User may hit the 'Return' key while typing the MSG, but this is NOT

%     recommended, as the formatting will not be preserved on decoding,

%     and the string length counter will not display the correct string

%     length.  Similarly for the 'Tab' key, use spaces instead.

% 2.  User should NOT hit the 'Return' key as part of the decoding KEY.

if nargin==0

   arg = 'initialize';

else

    % Retrieve/redefine (See definitions below) Mainly for easy reading.

    hands = get(gcf,'userdata');

    pos = get(gcbf,'position');

    checkd = hands(1); % For user to choose to decode a MSG.

    checke = hands(2); % For user to choose to encode a MSG.

    edit1 = hands(3);  % Space for user to enter MSG.

    edit2 = hands(4);  % Space for user to enter key.

    frame1 = hands(5);

    frame2 = hands(6);

    push1 = hands(7);  % Indicates user is done entering MSG.

    push2 = hands(8);  % Indicates user is done entering KEY.

    static1 = hands(9);

    static2 = hands(10);

    static3 = hands(11);

    static4 = hands(12);

    static5 = hands(13);

end

switch arg

    case 'initialize'  % Creation of GUI and storage of handles.

    counter=0;  % This is where the length of MSG is stored.

    h_fig = figure('name','Text Hider','position',[460 760 300 80],...

                   'menubar','none','resize','off');                                               

    col = get(h_fig,'color');

    checkd=uicontrol(h_fig,'style','checkbox','position',[140 20 60 20],...

                    'string','Decode','backgroundcolor',col,'callback',...

                    'txthide(''decode'')','fontweight','bold');

    checke=uicontrol(h_fig,'style','checkbox','position',[140 50 60 20],...

                    'string','Encode','fontweight','bold',...

                    'backgroundcolor',col,'callback',...

                    'txthide(''encode'')');

    edit1=uicontrol(h_fig,'style','edit','horizontalalignment','left',...

                    'max',9,'min',1,'visible','off','KeyPressFcn',...

                    'txthide(''count'')','userdata',counter);

    edit2=uicontrol(h_fig,'style','edit','horizontalalignment','left',...

                    'max',9,'min',1,'visible','off');

    frame1=uicontrol(h_fig,'style','frame','visible','off');

    frame2=uicontrol(h_fig,'style','frame','visible','off');

    push1=uicontrol(h_fig,'style','pushbutton','string','done',...

                   'callback','txthide(''done1'')','visible','off');

    push2=uicontrol(h_fig,'style','pushbutton',...

                   'string','done','callback','txthide(''done2'')',...

                   'visible','off');

    static1=uicontrol(h_fig,'style','text','visible','off',...

                     'string','Enter the message you wish to hide.',...

                     'fontweight','bold','backgroundcolor',col);               

    static2=uicontrol(h_fig,'style','text','position',[30 33 75 20],...

                      'strin','Choose one:','fontweight','bold',...

                      'backgroundcolor',col);          

    static3=uicontrol(h_fig,'style','text','visible','off',...

                     'string','Enter the key for decoding.',...

                     'fontweight','bold','backgroundcolor',col);

    static4=uicontrol(h_fig,'style','text','visible','off',...

                     'string','Message Length:',...

                     'fontweight','bold','backgroundcolor',col);

    static5=uicontrol(h_fig,'style','text','visible','off',...

                     'string','0','foregroundcolor','blue',...

                     'fontweight','bold','backgroundcolor',col);

    hands=[checkd checke edit1 edit2 frame1 frame2 push1 push2 static1...

           static2 static3 static4 static5];

    set(h_fig,'userdata',hands);  % Store handles in figures userdata.

   

    case 'encode' % The user has chosen to encode a MSG.

        set(gcbf,'position',[pos(1) pos(2)-300 300 380]);

        set(checkd,'enable','off','position',[140 320 60 20]);

        set(checke,'position',[140 350 60 20],'enable','off');

        set(edit1,'visible','on','position',[30 50 245 200],'fontsize',...

            10,'string',['     Maximum Number of Characters  ',...

            '         is 1000. See Counter Below'],'foregroundcolor',...

            'red');  % Issue a reminder about the max MSG length.

        set(frame1,'visible','on','position',[30 295 245 3],...

            'backgroundcolor','black');

        set(push1,'visible','on','position',[230 10 45 28]);

        set(static1,'visible','on','position',[30 260 245 20]);

        set(static2,'position',[30 333 75 20]);

        set(static4,'visible','on','position',[28 4 100 28]);

        set(static5,'visible','on','position',[130 4 50 28]);

        pause(1.75);  % Displays reminder only a short time.

        set(edit1,'foregroundcolor','black','string','','fontsize',9)

       

    case 'decode'  % The user has decided to decode a MSG.

        set(gcbf,'position',[pos(1) pos(2)-110 300 190]);

        set(checkd,'enable','off','position',[140 130 60 20]);

        set(checke,'enable','off','position',[140 160 60 20]);

        set(edit2,'visible','on','position',[30 40 245 30]);

        set(frame1,'position',[30 110 245 3],'visible','on',...

            'backgroundcolor','black');

        set(push2,'visible','on','position',[130 7 45 28]);

        set(static2,'position',[30 143 75 20]);

        set(static3,'visible','on','position',[30 75 245 20]);

       

    case 'done1'  % The user is done entering the MSG to encode.

         set(gcbf,'position',[pos(1) pos(2)-140 300 520]);

         set(checkd,'position',[140 460 60 20]);

         set(checke,'position',[140 490 60 20]);

         set(edit1,'position',[30 190 245 200],'enable','off');

         set(edit2,'visible','on','position',[30 60 245 30]);

         set(frame1,'position',[30 435 245 3]);

         set(frame2,'position',[30 133 245 3],'visible','on',...

             'backgroundcolor','black');

         set(push1,'position',[230 150 45 28],'enable','off');

         set(push2,'visible','on','position',[130 20 45 28]);

         set(static1,'position',[30 400 245 20]);

         set(static2,'position',[30 473 75 20]);

         set(static3,'visible','on','position',[30 95 245 20]);

         set(static4,'position',[28 144 100 28]);

         set(static5,'position',[130 144 50 28])

         if isempty(get(edit1,'string')) % User tried to encode nothing!

               fprintf('\n\t\t No message entered, try again.\n\n')

               close(gcbf)

               return

         end

        

    case 'done2'  % User has entered the key for use in encoding/decoding.

        en_or_de = get(checke,'value'); % Is user encoding or decoding?

        if en_or_de==1 % Encoding.

           key = get(edit2,'string');

           if isempty(key)  % Check if user tried to encode with no KEY.

              fprintf('\n\t\t No key entered, try again.\n\n');

              close(gcbf);

              return

           end

           msg = get(edit1,'string');

           [i j] = size(msg);  % Useful if user hit 'return' in MSG.

           if i >1

               msg = reshape(msg',1,i*j); % MSG should be 1 by n.

           end

           close(gcbf);

           wrkd = encode(msg,key);  % Pass to encode function.

           if isempty(wrkd)  % User hit cancel when choosing a file.

               close(gcbf);

               fprintf('\n\t\t Operation aborted.\n\n');

               return

            end

           fprintf('\t\t\n Your message was encoded.\n\n');

        else % Decoding.

            key = get(edit2,'string');

            if isempty(key)  % Check if user tried to dencode with no KEY.

               close(gcbf)

               fprintf('\n\t\t No key entered, try again.\n\n')

               return

            end

            msg=decode(key);  % Pass to decode function.

            if isempty(msg) % User hit cancel when choosing a file.

               close(gcbf)

               fprintf('\n \t\t Operation aborted.\n\n')

               return

            end

            close(gcbf);  % New figure is created next to display MSG.

            h_fig = figure('name','The Message','position',...

                         [460 460 300 380],'menubar','none');

                     col=get(h_fig,'color');

            stat = uicontrol(h_fig,'style','edit','position',...

                     [30 40 245 300],'string',msg,'fontsize',9,...

                     'horizontalalignment','left','max',9,'min',1);%#ok

            stat2 = uicontrol(h_fig,'style','text','position',...

                     [30 355 245 20],'string','Your Message:',...

                     'fontweight','bold','backgroundcolor',col,...

                     'horizontalalignment','left','fontsize',12);%#ok

        end

       

    case 'count' % This is where the length of MSG is counted.

        ch=get(gcbf,'currentcharacter');

        if isempty(ch) || ch==13

            return

        elseif ch==8

            counter = get(edit1,'userdata')-1;

        else

         counter = get(edit1,'userdata')+1;  % Retrieve current length.

        end

        set(edit1,'userdata',counter);

        set(static5,'string',num2str(counter));

        if counter > 990  % Issue a warning when getting close to limit.

           set(static5,'foregroundcolor','red');

        end

end  % End switch

%----------New Function Starts Below--------------------------------------

function success = encode(msg,key)

% ENCODE(msg,key) Encodes a text message using a key.

% This works by using the ascii number representation of the chars in

% KEY (and certain permutations) to create coordinate pairs that represent

% the places in matrix A (which is a submatrix of the pic matrix) where the

% unit alterations to the pic matrix will be made.  I tried to make the

% code easy to follow, but I will respond to questions about how this

% works.

num2add = 1000-length(msg);  % Number of spaces to add to end of MSG.

if num2add < 0, error('This message is too long to encode.'), end

newmsg = [msg,repmat(' ',1,num2add)]; % 1000 chars always encoded.

msgmat = dec2bin(newmsg)-48; % Each row is a bin. rep. of an ascii char.

[filen pth]=uigetfile({'*.bmp';'*.tif';'*.jpg'},'Choose Image To Encode.');

if isequal(filen,0) || isequal(pth,0)

    success = [];   return  % User cancelled.

end

pic1 = imread([pth filen]);  

B = pic1(:,:,1);   [piclngth pichght] = size(B);  % Choose the first page.

dim1 = piclngth-2;   dim2 = pichght-3;   keyb = key(end:-1:1);

rows = cumsum(double(key));  

columns = cumsum(double(keyb));  % Coord pairs for KEY (rows,columns)

A = zeros(dim1,dim2); % This matrix will house the hiding points.

A = crtmtrx(A,rows,columns,dim1,dim2,key);

idx = find(A==1);  % This same index will be used for pic matrix.

for vv = 1:1000  % This is the encoder.

    for uu = 1:7

        if msgmat(vv,uu)==1;

           if rem(B(idx(uu+7*(vv-1))),2)==0

              B(idx(uu+7*(vv-1))) = B(idx(uu+7*(vv-1)))+1;

           end

        elseif rem(B(idx(uu+7*(vv-1))),2)==1

              B(idx(uu+7*(vv-1))) = B(idx(uu+7*(vv-1)))-1;

        end

    end

end

newpic = pic1;   newpic(:,:,1) = B;

[filen pth] = uiputfile({'*.bmp';'*.tif'},'Save Encoded File As');

if isequal(filen,0) || isequal(pth,0)

    success = [];   return

end % User cancelled.

imwrite(newpic,[pth filen])

success = 1;

%----------New Function Starts Below--------------------------------------

function msg = decode(key)

% DECODE(key) Decodes the message hidden by encode in pic, using key.

[filen pth] = uigetfile({'*.bmp';'*.tif'},'Choose Image To Decode.');

if isequal(filen,0) || isequal(pth,0)

    msg = [];   return

end % User cancelled.

pic2 = imread([pth filen]);  

B = pic2(:,:,1);   [piclngth pichght] = size(B);  % Choose the top page.

dim1 = piclngth-2;   dim2 = pichght-3;   keyb = key(end:-1:1);

rows = cumsum(double(key));   columns = cumsum(double(keyb));

A = zeros(dim1,dim2);  % This matrix houses the hiding points.

A = crtmtrx(A,rows,columns,dim1,dim2,key);

idx = find(A==1);   msgmat = zeros(1000,7);

for vv = 1:1000  % This is the decoder.

    for uu = 1:7

        if rem(B(idx(uu+7*(vv-1))),2)==1

           msgmat(vv,uu) = 1;

        end

    end

end

msg = char(bin2dec(num2str(msgmat)))';

%----------New Function Starts Below--------------------------------------

function A = crtmtrx(A,rows,columns,dim1,dim2,key)

% Creates the matrix used to find the points to hide the message.

jj = 1;   idx = 1;

while 7000 > length(idx) %  Need 7000 points to hide 1000 characters.    

    for ii = 1:length(rows)

        if rows(ii) < dim1

           rows(ii) = rem(dim1,rows(ii))+1;

        else

           rows(ii) = rem(rows(ii),dim1)+1;

        end

        if columns(ii) < dim2

           columns(ii) = rem(dim2,columns(ii))+1;

        else

           columns(ii) = rem(columns(ii),dim2)+1;

        end

        A(rows(ii),columns(ii)) = 1;

    end

    rows = jj*cumsum(double(columns))+round(dim2/2);  % Each pass is diff.

    columns = jj*cumsum(double(rows))+round(dim1/2);

    if jj > ceil(7000/length(key))+2  % Estimate how many iters. needed.

       idx = find(A==1);

    end

   jj = jj+1;

end