Re: [WM]: On DFT/FFT-based Watermarking

[Amr Nasr <amr128@yahoo.com>]

Hello Mr.AMGee,
   the symmetric properties are simple 
  that means when you the fourier transform
 the output will be magnitude and phase angle
   the phase angle is critical so we will not change
it
 So we will work with the magnitude ,ok.
  In order to change the magnitude properly 
 we should know that the center frequency component at
the center of the magnitude matrix .
                 [.................]
                 [.................]
                 [........x........]
                 [.................]
                 [.................]
      like the x in the figure.
   any points around it changed , their mirror around
this point should be changed in the same manner.
  according to the symmetric property these values are
identical , and if they are not identical you will
face tough problems of the complex magnitudes
                               that is it. 
                                   AMR NASR   


______________________________________________________________________________

Watermarking Mailing List - http://www.watermarkingworld.org/ml.html
To unsubscribe send email to "majordomo@watermarkingworld.org" with
"unsubscribe watermarking YOURMAIL" in the body.
______________________________________________________________________________