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Lossless Recovery of a VQ Index Table with Embedded Secret Data. Chin-Chen Chang, Wen-Chuan Wu b, and Yu-Chen Hu Journal of Vision Communication and Image Representation, Vol. 18, 2007, pp. 207 – 216 Reporter: Jen-Bang Feng. VQ Compression. VQ compressed. Original image. Block size 2*2.
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Lossless Recovery of a VQ Index Table with Embedded Secret Data Chin-Chen Chang, Wen-Chuan Wu b, and Yu-Chen Hu Journal of Vision Communication and Image Representation, Vol. 18, 2007, pp. 207–216 Reporter: Jen-Bang Feng
VQ Compression VQ compressed Original image Block size 2*2 Size 512*512 24-bits per pixel 768 KBytes 256*256 indices 8-bits per index 64 KBytes Codebook size 256 = 28 256*4*24-bit = 3 KBytes
Embedding Secrets Original indices 0, 5, 4, 8, 20 • Extended Research: • Group clustering • Dynamic groups • CodeBook training Secret bits 1 0 1 0 0 Group 2 Group 1 Stego indices 1, 4, 5, 8, 20 CodeBook M. Jo, K.D. Kim, A digital image watermarking scheme based on vector quantization, IEICE Transactions on Information and Systems E85-D (6) (2002) 1054–1056.
1. The Pre-Processing Procedure • To reorganize the original VQ codebook of N codewords to facilitate the future embedding capacity
2. Clustering The most often used indices Cr, Cr+m, Cr+2m are closed to each other Only Cluster 1 is embedded with secrets Index number 0 is preserved for identity
3. Embedding Secrets Need only Floor( log2index/3) -bits
Another Example Index number 0 and 31 are preserved for identity
Number of Clustered Blocks • Only blocks are clustered. • B*3 blocks are one set
Ex. Results Not reversible Binary images
Conclusions • Reversible data hiding with VQ • Can not normally revealed until recover