Image_Steg

Image Steganograpy using Pixel-Value Differencing

clc;
close all;
clear;

%%%%%%%%%%%%%%%%%%%%%%% Reading a Secret Text File %%%%%%%%%%%%%%%%%%%%%%%%
file_id = fopen（‘message.txt‘‘r‘）;
file_content = fread（file_id）;
file_length = length（file_content）;
in = [];
in = [in dec2bin（file_length20）]; %character to binary conversion 
for i=1:file_length                                         
    in=[in dec2bin（file_content（i）7）];
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%% Reading Cover Image %%%%%%%%%%%%%%%%%%%%%%%%%%%
cover_image = imread（‘cover_image.bmp‘）; %get cover image                                        
red = cover_image（::1）; %seperating rgb values 
blue = cover_image（::2）;
green = cover_image（::3）;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% embedding Data %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
color = red; %red color selected for embedding
[rc] = size（color）;
final = double（color）; 
next=0;
capacity=0; %total no of bits that can be embedded

for x=0:1:r-1 
    for y=0:2:c-1
        enable = 1; %enable=0 when new pixels may fall off the boundary
        p = color（1+x1+y:2+y）; %block of two pixels pi & pi+1
        p = double（p）;
        d = p（12） - p（11）; %d = difference between 2 pixel
        d_abs = abs（d）; %absolute difference
        lb=[0 8 16 32 64 128]; %lowerbound
        ub=[7 15 31 63 127 255]; %upperbound
        for i=1:1:6 %test the R boundary
            if（（d_abs >= lb（i）） && （d_abs <= ub（i））） %selecting range
                %check if any pixel in a block fall off the boundary [0255]
                even2 = mod（d2）; 
                m2 = ub（i） - d;
                if （even2 == 0）
                    Pcheck=[p（11）-floor（m2/2） p（12）+ceil（m2/2）];
                else
                    Pcheck=[p（11）-ceil（m2/2） p（12）+floor（m2/2）];
                end
                if（Pcheck（1）<0 || Pcheck（2）<0 || Pcheck（1）>255 || Pcheck（2）>255）
                    enable = 0;
                    break
                end
                
                n = ub（i）-lb（i）+1; %quantization width of range
                t = floor（log2（n））; %maximum bit can be embedded in 2 pixels
                capacity=capacity+t; %max capacity of the cover image 
                
                %check if next exceeds the length of message
                if（next>length（in）） 
                    m=0;
                %check if next+t exceeds the length of message
                elseif（next+t>length（in）） 
                    if（1+next>=length（in））
                        k=zeros（1t）;
                    else
                        k=in（1+next:length（in））;
                    end
                    diff =next+t-length（in）;
                    k1=zeros（1t）;
                    if（diff>0）
                        for j=1:next+t-length（in）
                            k1（j）=k（j）;
                    

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----

     文件     786486  2012-05-12 18:09  Image_Steg\cover_image.bmp

     文件      12342  2012-05-09 23:43  Image_Steg\cover_image2.bmp

     文件       4951  2012-05-27 16:40  Image_Steg\data_embedding.m

     文件       2743  2012-05-27 21:24  Image_Steg\data_extraction.m

     文件       2735  2012-05-27 01:27  Image_Steg\histogram_analysis.m

     文件       4757  2012-05-27 18:15  Image_Steg\message.txt

     文件        923  2012-05-27 16:31  Image_Steg\psnr.m

     文件        897  2012-05-27 18:13  Image_Steg\Read Me Please!.txt

     目录          0  2012-10-10 13:30  Image_Steg

----------- ---------  ---------- -----  ----

               815834                    9