Feng-Hsing Wang

Bio: Feng-Hsing Wang is an academic researcher from University of South Australia. The author has contributed to research in topics: Digital watermarking & Watermark. The author has an hindex of 4, co-authored 8 publications receiving 391 citations.

A novel VQ-based watermarking scheme with genetic codebook partition

Abstract: A novel watermarking scheme based on vector quantisation (VQ) for digital still images is presented. This scheme begins with the procedure of partitioning the original codebook into two sub-codebooks. To achieve this, two strategies are proposed. The first one requires no complex algorithm and gives the users full freedom for partitioning. The second one is a genetic codebook partition procedure, which has the ability to improve the perfonmance of tile proposed watermarking scheme. After that, the information of codebook partition is served as a secret key and is used in the proposed watermarking scheme. In the embedding procedure, according to the watermark bit to be embedded a sub-codebook is chosen. The traditional VQ nearest codeword search is then performed to obtain the nearest codeword for the input vector. In the extracting procedure, the traditional VQ table lookup procedure is executed. With the same secret key, the hidden watermark bit can be determined by examining which same-codebook the corresponding codeword is belonging to. It is denaonstated that the proposed watermarking scheme provides better quality in watermarked images, stronger robustness under some common attacks, faster encoding time, and effective methods for partitioning codebooks.

VQ-Based gray watermark hiding scheme and genetic index assignment

Abstract: A vector quantisation (VQ) based watermarking scheme for hiding the gray watermark is presented. It expands the watermark size, and employs VQ index assignment procedure with genetic algorithm, called genetic index assignment (GIA), for watermarking. The gray watermark is coded by VQ, and obtained indices are translated into a binary bitstream with a much smaller size. We partition the codebook into two sub-codebooks, and use either one of them based on the value of the bit for embedding. Next, GIA is employed to find better imperceptibility of watermarked image. Experimental results show that the proposed method possesses advantages over other related methods in literature.

A multi-user based watermarking system with two-security-level keys

Abstract: This paper presents a new watermarking scheme to reduce the detection error probability through removal of local mean values of an original signal. It will be analytically proven that the removal process plays role in reducing the interference between an original signal and a watermark to be embedded. This is simply based on the orthogonality of the DC signal and the AC signal. As a result, the process improves the ability of the right detection. The proposed method is analytically and empirically evaluated with no attack as well as JPEG compression attacks.

International Conference on Intelligent Information Hiding and Multimedia Signal Processing

Abstract: This study presents a robust and semi-blind watermarking by embedding information into low frequency AC coefficients of Discrete Cosine Transform (DCT). Since the imperceptibility is the most significant issue in watermarking, the DC value is maintained unchanged. The proposed methods utilize the DC values of the neighboring blocks to predict the AC coefficients of the center block. The low frequency AC coefficients are modified to carry watermark information. The Least Mean Squares (LMS) is employed to yield the intermediate filters, cooperating with the neighboring DC coefficients to precisely predict the original AC coefficients. Two watermarking methods, namely Watermark Embedding in the Predicted AC Coefficient (WEPAC) and Watermark Embedding in the Original AC coefficient (WEOAC), are presented in this study. Moreover, many attacks are addressed to show the robustness of the proposed methods.

Optimized gray-scale image watermarking using DWT-SVD and Firefly Algorithm

Abstract: This paper presents an optimized watermarking scheme based on the discrete wavelet transform (DWT) and singular value decomposition (SVD). The singular values of a binary watermark are embedded in singular values of the LL3 sub-band coefficients of the host image by making use of multiple scaling factors (MSFs). The MSFs are optimized using a newly proposed Firefly Algorithm having an objective function which is a linear combination of imperceptibility and robustness. The PSNR values indicate that the visual quality of the signed and attacked images is good. The embedding algorithm is robust against common image processing operations. It is concluded that the embedding and extraction of the proposed algorithm is well optimized, robust and show an improvement over other similar reported methods.

A new approach for optimization in image watermarking by using genetic algorithms

Abstract: In this paper, the authors propose the spread spectrum image watermarking algorithm using the discrete multiwavelet transform. Performance improvement with respect to existing algorithms is obtained by genetic algorithms optimization. In the proposed optimization process, the authors search for parameters that consist of threshold values and the embedding strength to improve the visual quality of watermarked images and the robustness of the watermark. These parameters are varied to find the most suitable for images with different characteristics. The experimental results show that the proposed algorithm yields a watermark that is invisible to human eyes and robust to various image manipulations. The authors also compare their experimental results with the results of previous work using various test images.