Improving histogram-based reversible data hiding by interleaving predictive Source: IET Image Processing, Vol. 4, No. 4, Aug. 2010, pp.223-234 Authors : C.-H. Yang and M.-H. Tsai Speaker : Hon-Hang Chang Date : 2010/12/01

Outline Introduction Related work Proposed method Experiment results Conclusion

- = + = Introduction Histogram Difference Array D Cover image Predicted image + = Predicted image Stego-image Difference Array D’ Embed the secret bit 0 or 1

Related work D D D H Stego-image 62 56 63 60 61 59 58 55 57 x 6 7 3 2 Lin et al.’s method 62 56 63 60 61 59 58 55 57 x 6 7 3 2 1 4 x 7 8 4 3 1 5 x 7 8 4 3 1 2 5 Shift Embed D D D H Shift 63 56 64 60 62 59 58 54 55 Stego-image

Related work (Cont.) D D D Stego-image H x 7 8 4 3 1 2 5 x 7 8 4 3 1 5 Lin et al.’s method x 7 8 4 3 1 2 5 x 7 8 4 3 1 5 x 6 7 3 2 1 4 Extract Shift 63 56 64 60 62 59 58 54 55 D D D Stego-image 62 56 63 60 61 59 58 55 57 Shift H

Proposed method H D 5 4 6 3 2 5 1 4 -1 6 -2 3 Embedding in odd columns D1,1=H1,1-H1,2=5-5=0 5 4 6 3 2 5 1 4 -1 6 -2 3 D1,3=H1,3- ˻(H1,2+H1,4)/2˼ =5- 4= 1 D1,3=H1,5- H1,4 =4- 4= 0 H D Odd columns (Predicted pixels) Even columns(Sample pixels) D’s Histogram

Proposed method(Cont.) Embedding in odd columns 5 1 4 -1 6 -2 3 Podd1=0 Podd2=-1 Zodd1=2 Podd2=-3 D D’s Histogram 5 2 4 -1 6 -3 3 Shift Shift D D’s Histogram after shifting

Proposed method(Cont.) Embedding in odd columns Embed secret bit 0, no change!! Secret bits I: 01110011001 W1,1=W1,2+D1,1=5+0=5 W1,3=˻(W1,2+W1,4)/2˼+D1,3=4+2=6 W1,5=W1,4+D1,5=4+1=5 D’s Histogram after shifting Embed secret bit 1, changed to Podd2-1 or Podd1+1!! 5 6 4 3 1 5 2 4 -1 6 -3 3 5 2 4 1 -2 6 -1 -3 3 Embed Stego-image W1 D D

Proposed method(Cont.) Embedding in even columns 5 6 4 3 1 D1,2=H1,2- ˻(H1,1+H1,3)/2˼ =5- 5= 0 5 6 -1 4 3 2 1 -2 D1,4=H1,4- ˻(H1,3+H1,5)/2˼ =4-5=-1 W1 D Odd columns (Sample pixels ) Even columns(Predicted pixels) D’s Histogram

Proposed method(Cont.) 5 6 -1 4 3 2 1 -2 Embedding in even columns Shift Shift Podd1=2 Podd2=-1 Zodd1=4 Zodd2=-3 D D’s Histogram 5 6 -1 4 3 2 1 -3 D D’s Histogram after shifting

Proposed method(Cont.) Embedding in even columns Embed secret bit 0, no change!! Secret bits II: 01101 W1,2=˻(W1,1+W1,3)/2˼+D1,2=5+0=5 W1,4=˻(W1,3+W1,5)/2˼+D1,4 =5+(-1)=4 D’s Histogram after shifting Embed secret bit 1, changed to Podd2-1 or Podd1+1!! 5 6 4 7 3 1 2 5 6 -1 4 3 2 1 -3 5 6 -1 4 3 1 2 -2 -3 Embed Stego-image W2 D D

Proposed method(Cont.) D1,2= W1,2 -˻(W1,1+W1,3)/2˼ =5-5=0 D1,4= W1,4 -˻(W1,3+W1,5)/2˼ =4-5=-1 Extracting in even columns 5 6 -1 4 3 1 2 -2 -3 5 6 4 7 3 1 2 Podd1=2 Podd2=-1 D’s Histogram Zodd1=4 Zodd2=-3 Stego-image W2 D 5 6 -1 4 3 2 1 -2 5 6 4 3 1 D’s Histogram D Secret bits II: 01101 Stego-image W1

Proposed method(Cont.) D1,1=W1,1-W1,2=5-5=0 D1,3= W1,3 -˻(W1,2+W1,4)/2˼=6-4=2 D1,5=W1,5-W1,4=5-4=1 Extracting in odd columns 5 2 4 1 -2 6 -1 -3 3 5 6 4 3 1 Podd1=0 Podd2=-1 D’s Histogram Zodd1=2 Zodd2=-3 D Stego-image W1 5 4 6 3 2 5 1 4 -1 6 -2 3 D H Secret bits I: 01110011001 D’s Histogram

Proposed method(Cont.) Other predictive methods Figure 1 Chessboard with white pixels and black pixels

Experiment results Tabel 1 Compassion between the Lin’s method [4], Lin’smethod [5], Hsiao’s method [8] and our schemes with thechessboard interleaving prediction

Experiment results Table 2 Comparison of capacity, shifting numbers, changing numbers and PSNR values

Conclusion The proposed method achieve the larger capacity, but also keep the image quality better.