Palette Partition Based Data Hiding for Color Images Yu-Chiang Li, Piyu Tsai, Chih-Hung Lin, Hsiu-Lien Yeh, and Chien-Ting Huang Speaker : Yu-Chiang Li Date : 2009/09/13

2 Outline Introduction 1 Related Work 2 Proposed Scheme 33 Experimental Results 44 Conclusions 5

3 Introduction  Image data hiding employs original image to cover a secret message  Secret message is imperceptibly inserted into the original image

4 Introduction (c.)  Good data hiding technologies  Imperceptibility  High embedding capacity  Trade-off between  stego-image quality  hiding capacity

5 Introduction (c.)  Three categories of data hiding  Spatial domain  Frequency domain  Quantization domain

6 Introduction (c.) Spatial Domain  Secret message is directly embedded into spatial domain  Least-significant-bits Cover Image Secret Message inserted Stego-Image

7 Introduction (c.) Stego-Image Secret Message

8 Introduction (c.) Frequency Domain  Secret message is directly embedded into frequency domain Cover Image i i i i i i i i i i i i i41 - 9i i i i i i1 + 25i i i i i i i i i0 - 15i i i i i i0 - 8i6 - 8i8 + 0i6 + 8i0 + 8i i i i i i0 + 15i i i i i i i i i1 - 25i i i i i i41 + 9i i i i i Frequency Domain (Cover Image) Secret Message i i i i i i i i i i i i i41 - 9i i i i i i1 + 25i i i i i i i i i0 - 15i i i i i i0 - 8i6 - 8i9 + 0i6 + 8i1 + 8i i i i i i1 + 15i i i i i i i i i1 - 25i i i i i i41 + 9i i i i i Frequency Domain (Stego-Image) Stego-Image

9 Introduction (c.) Quantization Domaint  Quantization-based images such as vector quantization (VQ) Compress Codebook x x Uncompress m Codebook x x m

10 Related Work  Jo and Kim’s watermarking partitions the codebook into three sub-codebooks to hide watermark  Chang and Wu’s scheme clusters codewords with difference size and performs cycle permutation  Chiang and Tsai’s scheme divides the codebook into several sub-codebooks with codeword overlapping

11 Related Work (c.) Jo and Kim’s Watermarking  Jo and Kim’s technique partitions the codebook into three sub-codebooks

12 Related Work (c.) Embed Cover Image Watermark Embedded Image 01

13 Related Work (c.) Chiang and Tsai´s Scheme

14 Related Work (c.) Four-codeword Three-codeword Two-codeword One-codeword + Capacity(bit) Sub-cluster

15 Related Work (c.) Order in A Order in B Value in binary (0) (1) (2) (3) (4) (5) (6) (7) 22Unuse  Two codewords belongs to 3-member sub-cluster are considered together to embed three secret bits.

16 Proposed Scheme  Color Image Quantization Palette Index Table Palette Color Mapping Original Quantized

17 Proposed Scheme (c.)  Palette Partition Four-color Three-color Two-color One-color Capacity(bit) 2 1or Sub-palette

18 Proposed Scheme (c.)  Palette Partition with Overlapping Location0123 Four- color Three- color Two- color

19 Proposed Scheme (c.) Location 0123 Four- color (00) 2 (01) 2 (10) 2 (11) 2 Three- color (00) 2 (1) 2 (01) 2 Two-color (0) 2 (1) 2  Lookup table for embed data

20 Proposed Scheme (c.) Location0123 Four-color Three- color Two-color Location0123 Four-color(00) 2 (01) 2 (10) 2 (11) 2 Three- color (00) 2 (1) 2 (01) 2 NA Two-color(0) 2 (1) 2 NA Quantized Color Sub-palette Size3142 Embedded Color 147(1) 2 137(1) 2 146(00) 2 145(01) (00) 2 53(01) 2 15(01) 2 39(10) 2 47(11) 2 16(11) 2 125(0) 2 131(0) 2 149(1) 2 Case Quantized Color = 146 Secret Message 1110…. Sub-palette Size = replace 146 Secret Message “1” Embedded

21 Proposed Scheme (c.) Extraction Procedure Location0123 Four-color Three- color Two-color Location0123 Four-color(00) 2 (01) 2 (10) 2 (11) 2 Three- color (00) 2 (1) 2 (01) 2 NA Two-color(0) 2 (1) 2 NA 147 Index = 147 Secret Message = 1….

22 Experimental Results  RGB color images, “Airplane,” “Lena,” and “Pepper” of 512 × 512 pixels AirplaneLenaPepper Images Sub-Palette size Four-colorThree-colorTwo-color Airplane113(214)3(9)2(4) Lena146(236)2(4)1(2) Peppers71(141)5(12)22(42)

23 Experimental Results (c.) Sub-palette Four- color Three- color Two- color Estimated Capacity Airplane255,2162, ,478 Lena251,9383, ,532 Peppers197,04514,94726,457445,508 Performance of the proposed method MethodCQ Jo & Kim’sChiang& Tsai’sProposed PSNR Capacity RatioPSNRCapacityRatio PSNR CapacityRatio Airplane ,966 67, ,568 78, ,03778,632 Lena ,248 64, ,957 76, ,03677,010 Pepper ,756 62, ,020 73, ,98976,908 Average ,323 65, ,181 76, ,02077,499 Comparison: Ratio= Capacity/(CQ-PSNR)

24 Conclusions  An overlapping color palette partition based data hiding with improved data embedding procedure has been presented  Proposed method provides a largest hiding capacity and supports better stego-image quality than Chiang & Tsai’s method

26 Proposed Scheme Palette Partition Algorithm  Squared Euclidean Distance (SED) Euclidean Distance Image quantization Index1 Index2

27 Related Work (c.)  Chang & Wu’s Scheme  Clusters codewords with difference size  Performs cycle permutation  Embeded size in a group I = Index Embeded data

28 Experimental Results (c.) Sub-palette Four- color Three- color Two- color Estimated Capacity Airplane255,2162, ,478 Lena251,9383, ,532 Peppers197,04514,94726,457445,508 Performance of the proposed method MethodCQ Jo & Kim’sChang & Wu’sChiang& Tsai’sProposed PSNRCapacityPSNRCapacityPSNRCapacityPSNRCapacity Airplane , , , ,037 Lena , , , ,036 Peppers , , , ,989 Average , , , ,020 Ratio65,164696,74576,29477,499 Comparison: Ratio=Capacity/(CQ-PSNR)