java - Hiding message in JPG image -


i trying hide in image it's working fine .bmp & .png when write image jpg , try retrieve hidden message not working. procedure, first read image in format (bmp, gif, jpg,png) write message hide , save can again read , extract message. when save bmp or png works fine when saving jpg , try extract message doesn't work.

 imageio.write(bimg, "png", outputfile);//working  imageio.write(bimg, "png", outputfile);//not working

what should make work jpeg?

note: reading every pixel 4 bit integer argb value , changing lsb of r,g,b hide message.

    public void stegnography(bufferedimage bimg,string msg,string filename)     {        int w=bimg.getwidth();       int h=bimg.getheight();      //***************************************       // string msg="hide message:)";       system.out.println("message="+msg+" length="+msg.length());     //***************************************         if(msg.length()>255 )       {          jlabel3.settext("message large 255 characters");                   }       else if( msg.length()*11 >w*h)       {          jlabel3.settext("image small");           }       else{    //-------------------------------------------            byte[] msgbytes= msg.getbytes();          int msglendecode= (bimg.getrgb(0,0)>>8)<<8;           msglendecode |= msg.length();         bimg.setrgb(0, 0,msglendecode );//hidig msg length @ first position           //system.out.println("\npixel @ position (0,0) ");          // bitpattern(bimg.getrgb(0,0) );           for(int i=1,msgpos=0,row=0,j=0;   row<h   ;row++  )       {           for(int col=0;col<w && j<msgbytes.length ;col++,i++ )           {                       if (i%11==0) {                      int rgb = bimg.getrgb(col,row);                       int a=((rgb >> 24) & 0xff);                      int r = (((rgb >> 16) & 0xff)>>3)<<3;                     r=r|(msgbytes[msgpos]>>5);                      int g = (((rgb >> 8) & 0xff)>>3)<<3;                     g=g|((msgbytes[msgpos]>>2)& 7);                       int b = ((rgb & 0xff)>>2)<<2;                     b=b|(msgbytes[msgpos]&0x3);                       rgb=0;                     rgb=(rgb|(a<<24));                     rgb=(rgb|(r<<16));                     rgb=(rgb|(g<<8));                      rgb=(rgb|b);                      bimg.setrgb(col,row,rgb);                      msgpos++;                     j++;                    //bitpattern(bimg.getrgb(col,row));                }             }//for 2       }//for 1         imageicon image = new imageicon(bimg);            jlabel3.seticon(image);         try {    //  file outputfile = new file("c:/users/yathestha/documents/"+filename);      file outputfile = new file("c:/users/yathestha/documents/outpng.png");     imageio.write(bimg, "png", outputfile); } catch (ioexception e) {          system.out.println("error in saving image "); }    //-------------------------------------------------       }//else  // decoding part----------------------------------------------------------------------         } /////////////////////////////////////////////////////////////////////// private void decodestegnography(bufferedimage bimg) {       system.out.println("in decode");     int w=bimg.getwidth(),h=bimg.getheight();     bitpattern(bimg.getrgb(0, 0));     int msglength=(bimg.getrgb(0, 0)&0xff);     bitpattern(msglength);     system.out.println("message length="+msglength);      jtextfield1.settext("");       for(int row=0,j=0,i=1;   row<h   ;row++  )   {        for(int col=0;col<w && j<msglength ;col++ ,i++)       {            if (i%11==0) {              int result=bimg.getrgb(col,row);                 int charatpos = (((result >> 16) & 0x7) << 5);                charatpos |=  (((result >> 8) & 0x7) << 2);                charatpos |=  ((result & 0x3));                jtextfield1.settext(jtextfield1.gettext()+ (char)charatpos);               j++;           }       }   }        system.out.println("decoding done"); }//function

for jpeg steganography either save result lossless jpeg, or use different stegographic method. 1 know fiddling discrete cosine transform coefficients (dct). however, need aware of rounding errors , such retrieval of secret lossy.

i don't favour dct , haven't looked lot, here paper 2007 claims jpeg lossless steganography. warned algorithm more complex casual lsb substitution in spatial domain. hiding data in frequency domain means lower hiding capacity , don't know whether serve you. if interested , can't access paper, can sort out privately.


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