Browsing by Author "Shen, Chang-Hsing"

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Differential energy based watermarking algorithm using wavelet tree group modulation (WTGM) and Human Visual System
(2008-08-01)
Tsai, Min-Jen
;
Shen, Chang-Hsing
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Wavelet tree based watermarking algorithms are using the wavelet coefficient energy difference for copyright protection and ownership verification. WTQ (Wavelet Tree Quantization) algorithm is the representative technique using energy difference for watermarking. According to the cryptanalysis on WTQ, the watermark embedded in the protected image can be removed successfully. In this paper, we present a novel differential energy watermarking algorithm based on the wavelet tree group modulation structure, i.e. WTGM (Wavelet Tree Group Modulation). The wavelet coefficients of host image are divided into disjoint super trees (each super tree containing two sub-super trees). The watermark is embedded in the relatively high-frequency components using the group strategy such that energies of sub-super trees are close. The employment of wavelet tree structure, sum-of-subsets and positive/negative modulation effectively improve the drawbacks of the WTQ scheme for its insecurity. The integration of the HVS (Human Visual System) for WTGM provides a better visual effect of the watermarked image. The experimental results demonstrate the effectiveness of our algorithm in terms of robustness and imperceptibility.
Multipurpose Image Watermarking Based on the Wavelet Tree Contrast Level Transformation
(2009)
Tsai, Min-Jen
;
Shen, Chang-Hsing
;
Liu, Jung
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Multipurpose image watermarking algorithms can achieve the goal of content authentication and copyright protection simultaneously. In this paper, we propose a wavelet tree based blind watermarking algorithm using contrast level transformation. The wavelet coefficients of the host image are grouped into trees. The robust watermark and the semi-fragile watermark are embedded by quantizing one tree and resetting the other. With level change compensation, the watermarked image has high fidelity to the original one since the difference is minimized. Both of the watermarks can be independently extracted without the original image. The simulation results have demonstrated the effectiveness of the proposed algorithm in terms of robustness compared with other wavelet tree based technique.
Wavelet tree group modulation (WTGM) for digital image watermarking
(2007)
Tsai, Min-Jen
;
Shen, Chang-Hsing
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Differential Energy Watermarking (DEW) based techniques have been applied in DEW, modified schemes of DEW or Wavelet Tree Quantization (WTQ) algorithms by differentiating the transformed coefficient energy to verify the watermark embedding for copyright protection and ownership verification. In this paper, we present a novel differential energy watermarking algorithm based on the wavelet tree group modulation (WTGM) structure. The wavelet coefficients of the image are divided into disjoint tree groups and each tree group contains two sub tree groups. The watermark is embedded in the tree components using the group strategy such that the energy of tree groups is close and each subgroup performs different modulation for watermark embedding. Therefore, the employment of wavelet tree structure, sum-of-subsets and positive/negative modulation effectively improve the watermark robustness. In addition, the contrast sensitive function (CSF) and noise visibility function (NVF) of human visual system are also considered for the better visual quality of the watermarked image. The experimental results demonstrate the effectiveness of WTGM algorithm in terms of robustness and imperceptibility of watermarking.