[WM]: Re: basic DCT Watermarking problem

["Thai, Hien Duy" <tdhien@augusta.eee.u-ryukyu.ac.jp>]

Dear Gomper,

You should again verify step by step, in your program, which step makes =
the data distortion.

Such as, how to add 3  bits  of  binary  original  image A (bit =
8,7,6)=1B$B!!=1B(Bto A_dct_bit (bit 2,1,0) ??

Anyway the best basic DCT based image watermarking should be M. =
Barni=1B$B!G=1B(Bs papers, you can download from internet, (go google )

I suggest very simple algorithm for DCT and binary watermark, you can =
contact me for this simple code.



---- Embbeding --------------------------------------------------------
1. Make a DCT of original image
2. Permulation of binary image watermark (random)

4. Zigzag scan to separate frequency components to embed

3. Embedding the permutated watermark to some frequency components

4.Invert Zigzag
5. Inverse DCT to obtain a watermarked image (calculate PSRN and MSE)
------ Extraction-------------------------------------------------
1. Make a DCT for watermarked image and original image, respectively

4. Zigzag scan to separate frequency components to embed
2. Subtracting the frequency components of original image, from that of
  watermarked image to obtain the frequency components of watermark.
3. De-permulated
3. Make binarization the extracted watermark image
-------------------------------------------------------------------

Best regards

Tdhien



----- Original Message -----=20
From: "Gomper" <gomper@wp.pl>
To: <watermarking@watermarkingworld.org>
Sent: Friday, June 03, 2005 7:08 PM
Subject: [WM]: basic DCT Watermarking problem


> Dear Watermarkers!
>
>   Im using DCT transform for embendding watermark into the image.
>
>   this are steps i make to embend it and restore:
>   1. making DCT on whole image oryginal image  A_dct=3D dct2(A)
>   2.   substract   minimum   of   dct   coefficients   A_dct=3DA_dct  =
-
>   min(min(A_dct));
>   3. rounds and binaryzing all coefficients  -> A_dct_bit ;
>   each AC is writen on 16bits, A_dct(1:1)=3DDC -> length 16 bit
>   4.  Adds  3  bits  of  binaryzed  oryginal  image  A (bit 8,7,6) to
>   binaryzed coefficient A_dct_bit (bit 2,1,0)
>   5. back to decimal
>   6. inverse DCT
>
>   problem I have is that i cant extract corect watermark in restoring
>   process:
>   1. the same as above
>   2. the same as above
>   3. the same as above
>   4. extract watermark from bits 2,1,0
>   5. the same as above
>   6. the same as avove
>
>   when  restoring  is  over,  extracted  watermark  is different then
>   embendded, but there was no attack.
>
>   i  realize  that  some  mistake  is  in  embendding  watermark  or
>   restoring, but cant see it.
>
>   im not hiddeing dct(watermark) but only watermark so is it possible
>   that this is wrong? if yes, tell me please how to do this correct.
>
>   Im trying implement most simple embandding algorithm as possible so
>   I will apriciate for any suggestions or papers.
>
> --
> best regards,
> Gomper                          mailto:gomper@wp.pl


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