1. ISSCS 2009, Iasi, Romania1 On the Choice of the Mother Wavelet for Perceptual Data Hiding Corina Nafornita, Alexandru Isar Politehnica University of Timisoara Email: {corina.nafornita, alexandru.isar@etc.upt.ro}

2. ISSCS 2009, Iasi, Romania2 Goal Perceptual data hiding in the wavelet domain What is the “best” mother wavelet ? JPEG2000 standard

3. ISSCS 2009, Iasi, Romania3 Barni et al., 2001 Daubechies-6 Mask Watermark Original Marked DWT IDWT

4. ISSCS 2009, Iasi, Romania4 Artifacts  low resolution mask High resolution mask Watermark can easily be erased Use all resolution levels (not addresed here) Pros & cons Simple implementation No need of original image

5. ISSCS 2009, Iasi, Romania5 Mask estimation Low resolution vs. High resolution (Barni et al.,2001) (Nafornita et al.,2006)

6. ISSCS 2009, Iasi, Romania6 Choice of the mother wavelet Both methods use Daubechies-6. What is the best choice for the mother wavelet? Set: db2, db3, … db7 (n vanishing moments) Daubechies 9/7 (bior4.4), 5/3 LeGall (bior2.2) – used in JPEG2000 standard

7. ISSCS 2009, Iasi, Romania7 Test images Lena Picasso Texmos1p.512 Baboon

8. ISSCS 2009, Iasi, Romania8 Region segmentation Criterion: normalized local standard deviation 1/Homogeneous 0  0.045 2/Textures 0.045  0.35 3/Contours 0.35  1

9. ISSCS 2009, Iasi, Romania9 Invisibility: PSNR Image / Mother wavelet db2db3db4db5db6db7bior4.4bior2.2Barni Lena37.9238.1638.2838.3338.3538.4138.2635.9736.39 Picasso33.9734.0434.1534.2534.2734.3534.0232.0735.95 Texmos1p.51228.0928.2128.2828.2628.2928.3328.2826.0829.04 Baboon33.3033.3933.4033.4333.4633.4733.3031.3233.33

10. ISSCS 2009, Iasi, Romania10 JPEG compression, Q=50

11. ISSCS 2009, Iasi, Romania11 Median filtering, 3x3

12. ISSCS 2009, Iasi, Romania12 Resizing, 3/4

13. ISSCS 2009, Iasi, Romania13 Cropping, 256x256

14. ISSCS 2009, Iasi, Romania14 JPEG2000, CR=20

15. ISSCS 2009, Iasi, Romania15 Conclusions For the perceptual watermarking using the DWT the “best” mother wavelet bior2.2 recommended in the JPEG2000 standard In most cases, Nafornita et al. 2006 using mother wavelet bior2.2 outperforms Barni et al., 2001 using Daubechies-6 kernel bior2.2 – more compact support, suitable for edges (contours)