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Chou C.-H.,Tatung University | Liu K.-C.,Information Educating Center
IEEE Transactions on Image Processing | Year: 2010

Transparency and robustness are two conflicting requirements demanded by digital image watermarking for copyright protection and many other purposes. A feasible way to simultaneously satisfy the two conflicting requirements is to embed high-strength watermark signals in the host signals that can accommodate the distortion due to watermark insertion as part of perceptual redundancy. The search of distortion-tolerable host signals for watermark insertion and the determination of watermark strength are, hence, crucial to the realization of a transparent yet robust watermark. This paper presents a color image watermarking scheme that hides watermark signals in most distortion-tolerable signals within three color channels of the host image without resulting in perceivable distortion. The distortion-tolerable host signals or the signals that possess high perceptual redundancy are sought in the wavelet domain for watermark insertion. A visual model based upon the CIEDE2000 color difference equation is used to measure the perceptual redundancy inherent in each wavelet coefficient of the host image. By means of quantization index modulation, binary watermark signals are embedded in qualified wavelet coefficients. To reinforce the robustness, the watermark signals are repeated and permuted before embedding, and restored by the majority-vote decision making process in watermark extraction. Original images are not required in watermark extraction. Only a small amount of information including locations of qualified coefficients and the data associated with coefficient quantization is needed for watermark extraction. Experimental results show that the embedded watermark is transparent and quite robust in face of various attacks such as cropping, low-pass filtering, scaling, media filtering, white-noise addition as well as the JPEG and JPEG2000 coding at high compression ratios. © 2006 IEEE. Source


Liu K.-C.,Information Educating Center
AEU - International Journal of Electronics and Communications | Year: 2010

In this paper, a wavelet-based watermarking scheme for color images is proposed. The watermarking scheme is based on the design of a color visual model that is the modification of a perceptual model used in the image coding of gray scale images. The model is to estimate the noise detection threshold of each wavelet coefficient in luminance and chrominance components of color images in order to satisfy transparency and robustness required by the color image watermarking technique. The noise detection thresholds of coefficients in each color component are derived in a locally adaptive fashion based on the wavelet decomposition, by which perceptually significant coefficients are selected and a perceptually lossless quantization matrix is constructed for embedding watermarks. Performance in terms of robustness and transparency is obtained by embedding the maximum strength watermark while maintaining the perceptually lossless quality of the watermarked color image. Simulation results show that the proposed scheme is more robust than the existing scheme while retaining the watermark transparency. © 2008 Elsevier GmbH. All rights reserved. Source


Liu K.-C.,Information Educating Center
IET Image Processing | Year: 2014

In this study, the watermarking issue for colour image authentication is presented to resist malicious tampering. The objective of this study is to preserve the colour moments such that the tampered region of the colour image can be recovered with high quality. An input colour image is first partitioned into non-overlapping blocks for watermark embedding. The watermark information embedded into each block consists of the authentication data and the feature information that is given by the bi-level moment-preserving technique. In the proofing process, the authors propose a two-stage dual parity-check method and use morphological operations to prove the validity of the image blocks. The former is proposed to check two set dual authentication data for obtaining better results of tamper proofing and the latter is used to further improve the neighbourhood connectivity of the results. In the recovery process, the feature information of each block is rebuilt for reconstruction. The simulation results show that the proposed self-embedding watermarking scheme is able to effectively prove the tempered region with high detection rate and recover the tempered region with high quality. Meanwhile, the proposed scheme outperforms the relevant existing methods. © The Institution of Engineering and Technology 2014. Source


Liu K.-C.,Information Educating Center
Proceedings - 2011 4th International Conference on Information Management, Innovation Management and Industrial Engineering, ICIII 2011 | Year: 2011

In this paper, a perceptual JPEG2000 compliant coder based on the just noticeable distortion (JND) for the color images is presented. Since the human visual perception to color visual signals has a limited sensitivity, any change below the visibility threshold cannot be detected by human eyes. We therefore propose a new color JND estimator to incorporate into the design of the perceptual JPEG2000 coder. Without introducing the perceptual distortion into input signals, the dynamic range of input signals in each color component of the color image is reduced to increase the compression performance. In the simulation results, the bit rate required by the perceptual JPEG2000 compliant coder is lower than that required by the standard JPEG2000 coder at the perceptually lossless visual quality of the reconstructed color image. © 2011 IEEE. Source


Liu K.-C.,Information Educating Center
European Signal Processing Conference | Year: 2011

In this paper, a prediction error preprocessor based on the just noticeable distortion (JND) for the color image compression scheme is presented. The variance of prediction error signals we can reduce, the less objective distortion of the reconstructed image we can achieve at a given bit rate or the lower bit rate of the reconstructed image we can obtain at the same visual quality. Since the human visual perception to color visual signals has a limited sensitivity, any change below the visibility threshold cannot be detected by human eyes. We therefore use a new color JND estimator that is incorporated into the design of the prediction error preprocessor in the color image compression scheme. Without introducing the perceptual distortion into prediction error signals, the dynamic range of prediction error signals for coefficients in each color component of the color image is reduced to increase the compression performance. The estimated JND is also incorporated into the design of the quantization stage in the color image compression scheme. In the simulation results, the bit rate required by the compression scheme with the prediction error preprocessor is lower than that without the prediction error preprocessor at the consistent visual quality of the reconstructed color image. © 2011 EURASIP. Source

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