Robustness of the proposed progressive watermarking scheme

To evaluate the robustness of the proposed approach, the six test images were water-marked with the proposed watermarking approach. Then, four image processing oper-ations, JPEG compression, JPEG2000 compression, Gaussian filtering, and sharpening are applied on the watermarked images. The result images are shown in Fig. 4.5 to Fig.

4.10. The experimental results of applying four image processing operations are depicted in Fig. 4.11, Fig. 4.12 and Table 4.1.

As shown in Fig. 4.11, Fig. 4.12 and Table 4.1, even visual quality of the test image is largely decreased by the image processing operations, the watermark embedded in the image can still be detected by the proposed method. Thus, if someone tries to remove the watermark embedded in an image, the image processing operations will cause huge decrease to visual quality of the image such that the image will be of no commercial value.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked Lena image is 33.91. The percentage of correct watermark bits is 60.54%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked Lena image is 37.47. The per-centage of correct watermark bits is 62.69%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked Lena image is 31.47. The percentage of correct watermark bits is 75.39%.

(d) Result image after sharpening. The PSNR comparing to watermarked Lena image is 31.74. The percentage of correct watermark bits is 99.9%.

Figure 4.5: The result images of applying four common image processing operations on watermarked Lena image.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked Baboon image is 23.88. The percent-age of correct watermark bits is 63.28%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked Baboon image is 32. The per-centage of correct watermark bits is 94.53%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked Baboon image is 21.37. The per-centage of correct watermark bits is 60.64%.

(d) Result image after sharpening. The PSNR comparing to watermarked Baboon image is 17.53. The percentage of correct watermark bits is 94.62%.

Figure 4.6: The result images of applying four common image processing operations on watermarked Baboon image.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked F16 image is 30.39. The percentage of correct watermark bits is 60.25%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked F16 image is 31.56. The per-centage of correct watermark bits is 61.03%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked F16 image is 26.6. The percentage of correct watermark bits is 68.84%.

(d) Result image after sharpening. The PSNR comparing to watermarked F16 image is 25.42. The percentage of correct watermark bits is 99.21%.

Figure 4.7: The result images of applying four common image processing operations on watermarked F16 image.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked Fishing Boat image is 28.67. The percentage of correct watermark bits is 61.03%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked Fishing Boat image is 31.76. The percentage of correct watermark bits is 67.38%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked Fishing Boat image is 25.59. The percentage of correct watermark bits is 66.99%.

(d) Result image after sharpening. The PSNR comparing to watermarked Fishing Boat image is 23.56. The percentage of correct watermark bits is 98.82%.

Figure 4.8: The result images of applying four common image processing operations on watermarked Fishing boat image.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked Sailboat image is 28.48. The per-centage of correct watermark bits is 60.54%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked Sailboat image is 31.98. The percentage of correct watermark bits is 78.41%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked Sailboat image is 25.16. The per-centage of correct watermark bits is 64.35%.

(d) Result image after sharpening. The PSNR comparing to watermarked Sailboat image is 23.15. The percentage of correct watermark bits is 99.31%.

Figure 4.9: The result images of applying four common image processing operations on watermarked Sailboat image.

(a) Result image after JPEG compression. The PSNR com-paring to watermarked Peppers image is 31.7. The percent-age of correct watermark bits is 60.54%.

(b) Result image after JPEG2000 compression. The PSNR comparing to watermarked Peppers image is 33.97. The percentage of correct watermark bits is 57.12%.

(c) Result image after Gaussian filtering. The PSNR com-paring to watermarked Peppers image is 28.5. The percent-age of correct watermark bits is 71.28%.

(d) Result image after sharpening. The PSNR comparing to watermarked Peppers image is 26.34. The percentage of correct watermark bits is 99.31%.

Figure 4.10: The result images of applying four common image processing operations on watermarked Peppers image.

12 13 14 15 16 17 18 19 20

% of correct watermark bits Baboon

F16 Fishboat Lena Peppers Sailboat

Figure 4.11: The plot of percentage of correct watermark bits versus JPEG quality factor. Six water-marked images were compressed by JPEG.

30 32 34 36 38 40 42 44 46 48

PSNR of images compressed by J2K

% of correct watermark bits Baboon

F16 Fishboat Lena Peppers Sailboat

Figure 4.12: The plot of percentage of correct watermark bits versus PSNR. Six watermarked images were compressed by JPEG2000.

Table 4.1: Experimental results of watermark detection after Gaussian filtering and sharpening.

Baboon F16 FishBoat Lena Peppers Sailboat

3 × 3 Gaussian filtering PSNR 23.36 30.84 28.92 36.52 31.86 28.89

% of correct bits 76.6 83.7 83.5 92.1 91.5 82.4

5 × 5 Gaussian filtering PSNR 21.37 26.60 25.59 31.47 28.50 25.16

% of correct bits 60.6 68.8 66.9 75.3 71.2 64.3

Sharpening PSNR 17.53 25.42 23.56 31.74 26.34 23.15

% of correct bits 94.6 99.2 98.8 99.9 99.3 99.3

These experimental results show that the proposed watermarking method is robust and can be used on the applications of copyright protection.

4.4.3 Earlier detection of the proposed progressive watermarking scheme