seektc.m

steganography tools to hide a text file in an image in true colour.

function seektc(u)
%-----------------------------------------------------------------------------------------  
%  SEEKTC
%  The program recovers a file of hidden text in an image with the program Hiddetc.  
%  
%  It requires of an initial keyword that allows decrypt the text and to recover the 
%  original. Is a word without numbers, (of up to 24 characters). 
%
%  The syntax is seektc. 
%
%  Author: Francisco Echegorri  
%  E-mail: [e-mail]  
%  Created in September of 2002.  
%-----------------------------------------------------------------------------------------
%  El programa recupera un archivo de texto oculto en una imagen con el 
%  programa Hiddetc(que funciona con imagenes en color verdadero-24bits
%  o en escala de grises,256 gamas de gris).
%  Requiere de una clave inicial que permite desencriptar el texto y 
%  recuperar el original.(hasta 24 letras)
%  La sintaxis es seektc.
%------------------------------------------------------------------------------------------
if nargin<1
   [u, pathname] = uigetfile('*.*', 'Select the Image');
buffer=pwd;
cd (pathname);
cd (buffer);
end
tic,X=imread(u);
dim=size(X);a=dim(1);b=dim(2);X=double(X);Y=fix(X/2)*2+1;Z=Y-X;p=1;
pot20=[2^19,2^18,2^17,2^16,2^15,16384,8192,4096,2048,1024,512,256,128,64,32,16,8,4,2,1]';
pot=[128,64,32,16,8,4,2,1]';m=Z(1,1:20,1)*pot20;car=8*m+20;
h=waitbar(0,'Recovering the hidden text in the Image');n=0;Z=uint8(Z);
for c=1:3
   for i=1:a
      if n<=fix(car/b)*b-b
         y(n+1:n+b)=Z(i,1:b,c);n=n+b;
         waitbar(n/(fix(car/b)*b-b),h)
        end
    end
 end
if length(size(Z))==2
   c=1;
end
y((n+1):(car))=Z(i,1:(car-n),c);close(h)
q=length(y);y=y(21:q);q=length(y);y=double(y);
t1=reshape(y,8,q/8)'*pot;F=t1;
save htext F
reordtext % Decrypt the text file.
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