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1

Tree Structure Based Data Hiding for Progressive Transmission Images

Tsai P.

Fundamenta Informaticae

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2010

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Vol. 98, nr 2/3

257-275

EN

Progressive image transmission (PIT) is supported by several encoders such as SPIHT, JPEG2000 and so on. However, few of data hiding scheme for progressive transmission images is designed. In this paper, tree-structure-based data hiding for set partitioning in hierarchical trees (SPIHT) images is proposed. The bit stream of SPIHT multi-stage encoded was structured of tree. The secret image can be progressively embedded into SPIHT bit trees. Experimental results showed the progressive image data hiding is achieved. The secret image is progressively embedded/extracted in SPIHT encoded images. Furthermore, a higher hiding capacity was provided in an earlier encoding which helped the secret image to be identified earlier. Also, an adaptive hiding capacity could be developed by using different tree structures. In comparison with Tsai et al.'s scheme, the proposed scheme had a higher hiding capacity and a better secret image quality.

2

New Bit Reduction of Vector Quantization Using Block Prediction and Relative Addressing

Hu Y-C., Tsai P., Lo C-C.

Fundamenta Informaticae

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2008

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Vol. 87, nr 3-4

313-329

EN

A low bit rate image coding scheme based on vector quantization is proposed. In this scheme, the block prediction coding and the relative addressing techniques are employed to cut down the required bit rate of vector quantization. In block prediction coding, neighboring encoded blocks are taken to compress the current block if a high degree of similarity between them is existed. In the relative addressing technique, the redundancy among neighboring indices are exploited to reduce the bit rate. From the results, it is shown that the proposed scheme significantly reduces the bit rate of VQ while keeping good image quality of compressed images.

3

Fast VQ Codebook Generation Method Using Codeword Stability Check and Finite State Concept

Tsai P., Hu Y-C., Yeh H-L.

Fundamenta Informaticae

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2008

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Vol. 87, nr 3-4

447-463

EN

The codebook design in the vector quantization scheme is important because it affects the image quality of the encoded image. The Linde-Buzo-Gray (LBG) codebook generation algorithm is well known and a popular choice among codebook users. However, a heavy computational complexity is consumed for the iteratively clustering process in the LBG algorithm. In this paper, the similarity of codewords in consecutive rounds of the LBG algorithm is exploited to reduce the computational complexity. By checking the stability of codewords, the status of each codeword in the codebook can be determined. Only the unstable codewords are refined to generate the new codebook. The proposed method can be further improved by cooperating with the finite state technique. Experimental results show that the computational complexity of the proposed method is reduced to about 4% of the LBG algorithm while achieving a slightly worse image quality.

4

Codebook Partition Based Steganography without Member Restriction

Chiang Y-K., Tsai P., Huang F-L.

Fundamenta Informaticae

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2008

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Vol. 82, nr 1-2

15-27

EN

The practice of concealing secret messages into index-based images has generally suffered from problems of image quality degradation and hiding capacity restriction. A steganographic scheme using an improved codebook partition is proposed in this paper. The proposed scheme partitions the codebook into different member sub-clusters in terms of their similarity between the codewords for increasing the hiding capacity and reducing the image distortion. Any size of a sub-cluster was allowed in the proposed scheme, so as to improve the traditional approaches in which the size of a sub-cluster was restricted to the power of two. As a result of this revised scheme, an increased hiding capacity and a reduction in image distortion are obtained, as indicated from experimental results. The average performance of the proposed scheme is superior to that of those standard methods.

5

An Adaptive Steganographic Scheme for Color Images

Chang C.-C., Tsai P., Lin M.-H.

Fundamenta Informaticae

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2004

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Vol. 62, nr 3,4

275--289

EN

In this paper, a new palette-based image steganography is proposed. Palette-based images such as GIF files have been widely used on the Internet and web pages such that all browsers can recognize them. Palette-based images can be used as good carriers for transmitting secret messages. In this scheme, the Least Significant Bits (LSBs) of the palette-based image are utilized in order to hide the secret message by using the computational information hiding technique. The adaptive hiding capacity can be computed according to different sizes of the embedding block. Experimental results also show that existing artifacts in the traditional LSB-based method are unnoticeable. The number of modification pixels in the embedding process is decreased, while good stego-image quality is maintained, and the cover image is left unblemished by camouflaged information. Furthermore, the feature of adaptive hiding capacity provides the possibility of protecting different sizes of embedded secret messages.