An Algorithm for Removable Visible Watermarking Source: Circuits and Systems for Video Technology, Vol 16,  Issue 1,  Jan. 2006, pp. 129 – 133 Authors: Yongjian Hu, Kwong S, and Jiwu Huang. Speakers: Hong-Hang Chang. Date: 12. 21. 2009

Outline Introduction Related work Proposed scheme Experimental Result Conclusion

Introduction This is a original Image. And then, we can embedded the watermark to the original image by the information of the key. So if we have the original image, watermark and the key , we can embedded the watermark to the original image. Then, how can I extract the watermark from the watermarked image. The work is similar to the embedded work , we need a watermark and a key , then we can remove the watermark from the watermarked image soblutely.

HL HL LL LL LH LH HH HH Related work DWT LL2 HL2 LH2 HH2 LL HL HH LH 130 110 100 120 115 105 95 88 90 79 127 126 125 101 DWT LL LL2 HL2 HL HL 240 210 20 -10 235 200 5 10 178 167 -2 8 253 226 1 24 LL LL LH2 HH2 LH LH HH HH 475 410 25 431 393 -1 32 5 10 15 -20 -75 -59 -3 -16 LL HL HH LH

HL HL LH LH HH HH Proposed scheme LL2 HL2 LH2 HH2 LLK LHK HLK HHK LL2 HL2 HL HL LLK LH2 HH2 Low-Frequency Suspend LH LH HH HH LH HH HL HL2 LH2 HH2 k = the current scale of the DWT. K = the final scale of the DWT. High-Frequency Suspend

H W X Proposed scheme (Cont.) Suppose wh= 0.25 ww= 0.75 170 150 200 140 110 120 130 100 90 H 50 40 60 70 90 80 100 110 W Suppose wh= 0.25 ww= 0.75 170*0.25 + 50*0.75= 80 150*0.25 + 40*0.75= 67 . 90*0.25 + 90*0.75= 78 80 67 95 83 88 75 98 92 100 110 90 82 77 78 X

HL X Proposed scheme (Cont.) Low-Frequency Suspend Case1: take the H(1,1) for example. X(i,j) = the mean of the coefficients corresponding ‘0’ from nearest 8 neighbors . X(1,1)= (150+140)/2 =145 1 1 1 1 170 150 200 140 110 120 130 100 90 Case2: take the H(1,4) for example. X(i,j) = the mean of all the unchanged coefficients. X(1,4)= (170+150+…+77+78) / 16 = 91.625≈92 1 1 145 150 95 92 140 110 75 98 130 100 90 82 78 HL X

H W H W X Proposed scheme (Cont.) Low-Frequency Suspend 1 170 150 200 LH HH HL HL2 LH2 HH2 LH HH HL HL2 LH2 HH2 170 150 200 140 110 120 130 100 90 50 40 60 70 90 80 100 110 H W 170 150 140 120 130 90 100 50 40 70 90 80 200 150 110 120 100 140 90 130 H W X

Proposed scheme (Cont.) 1 40 20 5 160 50 90 -1 -5 -10 -20 4 -15 -30 High-Frequency Suspend 1 1 LH HH HL HL2 LH2 HH2 HLK LHK HHK Case1: take the H(1,2) for example. the mean of unchanged coefficients in its 8 neighbors. Case2: take the H(3,3) for example. the mean of unchanged coefficients in its 24 neighbors. Case3: take the H(4,4) for example. the mean of all unchanged coefficients . 40 5 20 160 50 90 -1 -5 3 -20 4 -15 1

Proposed scheme (Cont.) High-Frequency Suspend 40 5 20 160 50 90 -1 -5 3 -20 4 -15

Proposed scheme (Cont.) Retrieve A B C D E F G H I J K L M N O P 300 250 260 280 10 20 30 15 -2 -5 -1 7 5 …… a b c d e f g h i j k l m n o p 155 129 4 8 145 123 6 13 132 15 5 128 135 16 10 ……

Experiment result Fig. 1 PSNR (DB) OF RECOVERED IMAGES. LR AND ILR DENOTE LEGALLY AND ILLEGALLY RECOVERED IMAGES, RESPECTIVELY

Conclusion The experimental results have demonstrated that the legally obtained image has very high visual quality.