PRN BASED WATERMARKING SCHEME FOR COLOR IMAGES
Journal Name:
- İstanbul Ticaret Üniversitesi Fen Bilimleri Dergisi
Keywords (Original Language):
Author Name | University of Author |
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Abstract (2. Language):
Robust image watermarking is the process of embeddingan invisible watermark in an image in order to
make it very difficult to remove the watermark after intentional attacks and normal audio/visual processes.
A recent DWT-based semi-blind image watermarking scheme leaves out the low pass band, and embeds
the watermark in the other three bands into the coefficients that are higher than a given threshold T1.
During watermark detection, all the high pass coefficients above another threshold T2(T2> T1) are used in
correlation with the original watermark. In our extension to the DWT-based approach, we embed the same
watermark in two bands (LL and HH) using different scaling factors for each band. In the watermark
detection algorithm, the watermarked RGB (and possibly attacked) image is converted to the YUV model.
After computing the DWT of the luminance layer, all the DWT coefficients higher than a given threshold
T2 in the LL and HH bands are selected. The next step is to compute the sum Z, where i runs over all
DWT coefficients higher than a given threshold T2 in the LL and HH bands. In each band, if Z exceeds T,
the watermark is present. Experimental results indicate that detection in the LL band is robust for one
group of attacks, and detection in the HH band is robust for another group of attacks
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Abstract (Original Language):
Dayanikli resim damgalama gorunmeyen damganin kasitli saldiri ve goruntu islemlerinden sonra
damganin silinmesini oldukca zorlastiran resimlere gomulmesi islemidir. DWT ile yapilan yari-kor resim
damgalama yontemi LL bantini disari atip, digger uc bandin daha onceden belirlenen basmaktan buyuk
katsayilarina gomme yapilir. Damga Ortaya cikarma esnasinda ise, uc banttaki T2’den buyuk katsayilarin
gercek damga ile korelasyonu hesaplanir. Bizim genisletilmis DWT algoritmamizda ayni damgayi LL ve
HH bantlarina farkli katsayilar kullanarak gommekteyiz. Damga tespitinde ise damgalanmis RGB (ve
saldirilmis olmasi mumkun) resim YUV resim modeline cevrilir. Luminance tabakasi DWT’ye
cevrildikten sonra T2’den buyuk LL ve HH bantlari katsayilari secilir. Sonraki adimda ise toplam Z degeri
hesaplanir bu katsayilar icin. Eger Z degeri T degerinden buyuk ise resim damgalanmis, aksi takdirde
damgalanmamis demektir. Deney sonuclarimiz LL bantta gommek bir grup saldiriya karsi dayanikli
olurken, HH banta gomme diger bir grup saldiriya karsi dayanikli olmaktadir.
FULL TEXT (PDF):
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119-131