How do you convert an invisible watermark to visible watermark in DCT domain??

 x=1;
  y=1;
  for (kk = 1:length(message_pad)) 

dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1)); 

if (message_pad(kk) == 0)

   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

   elseif (message_pad(kk) == 1) 

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

   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 

watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=idct2(dct_block);

   if (x+blocksize) >= Nc

x=1;

y=y+blocksize;

else x=x+blocksize; 

end 

end