R.A. Qahwaji

Bio: R.A. Qahwaji is an academic researcher from University of Bradford. The author has contributed to research in topics: Digital watermarking & Watermark. The author has an hindex of 2, co-authored 2 publications receiving 31 citations.

A New Blind Image Watermarking of Handwritten Signatures using Low-Frequency Band DCT Coefficients

Abstract: This paper deals with a new blind technique for robust image watermarking in the DCT domain. The technique is based on embedding watermark information in eight low-frequency band coefficients of the DCT sub-blocks. Single watermark has been embedded multi-times in the host image. The embedding process is based on changing the selected DCT-coefficients of the host image to odd or even values depending on the binary watermark's bit value. The proposed blind watermarking embedding has shown to be strongly robust against several attacks.

A New Blind Image Watermarking Technique for Dual Watermarks Using Low-Frequency Band DCT Coefficients

Abstract: This paper deals with a new blind robust watermarking technique for embedding two watermarks into a host image. The technique is based on embedding watermark information in sixteen low-frequency band coefficients of the DCT sub-blocks. The embedding process is based on changing the selected DCT-coefficients of the host image to odd or even values depending on the binary watermark's bit value. The proposed blind watermarking embedding has shown to be strongly robust against several attacks.

A Video Watermarking Technique Based on Pseudo-3-D DCT and Quantization Index Modulation

Abstract: The increasing popularity of the internet means that digital multimedia are transmitted more rapidly and easily. And people are very aware for media ownership. However, digital watermarking is an efficient and promising means to protect intellectual properties. Based on the intellectual property attention in the information era, how to protect the personal ownership is extremely important and a necessary scheme. In this paper, we propose an effective video watermarking method based on a pseudo-3-D discrete cosine transform (DCT) and quantization index modulation (QIM) against several attacks. The watermark is mainly inserted into the uncompressed domain by adjusting the correlation between DCT coefficients of the selected blocks, and the watermark extraction is blind. This approach consists of a pseudo-3-D DCT, watermark embedding, and extraction. A pseudo-3-D DCT, which is taken DCT transformation twice, will be first utilized to calculate the embedding factor and to obtain the useful messages. Using the QIM, we embed the watermark into the quantization regions from the successive raw frames in the uncompressed domain and record the relative information to create a secret embedding key. This secret embedding key will further apply to extraction. Experimental results demonstrate that the proposed method can survive filtering, compressions, luminance change, and noise attacks with a good invisibility and robustness.

A Robust Evolutionary Based Digital Image Watermarking Technique in DCT Domain

Abstract: Digital watermarking techniques are used for the digital right managements and copyright protection. As known, it is a big deal in watermarking systems to make a good trade of between the robustness and imperceptibility. This paper presents a watermarking algorithm in the DCT domain using an evolutionary algorithm to satisfy both of robustness and imperceptibility. We employ a genetic-based algorithm to select pairs in DCT coefficients and insert watermark bit according to mathematical relation between selected coefficients in each 8×8 DCT block of image. The proposed method has been implemented and tested under various attacks including JPEG compression, additive noise distortion, and image filtering. The achieved results show that image remains imperceptible while the watermark survives the attacks especially in case of JPEG compression.

A Blind DCT Domain Digital Watermarking for Biometric Authentication

Abstract: In this paper, an efficient blind digital image watermarking algorithm using mapping technique is presented. The algorithm can embed or hide an entire image or pattern (logo) directly into the original image. The embedding process is based on changing the selected DCT coefficients of the host image to odd or even values depending on the binary bit value of watermark DCT coefficients. The algorithm is tested for fingerprint image embedded with a face watermark. It is demonstrated that the watermarking algorithm offers a significant advantage of providing biometric image compression and authentication without introducing any significant degradation in the image quality. Moreover the watermarking scheme is blind and does not require any additional data for logo extraction.

An Introduction to Robust Transform Based Image Watermarking Techniques

Abstract: One of the important applications of digital watermarking technology is copyright protection and ownership identification for digital images. To achieve this goal, robust watermarking has been rapidly developed in the past decade or so. Robust watermarking is designed to survive various non-geometric manipulations such as JPEG compression, additive noise and filtering as well as some geometric distortions such as rotation and scaling. In this chapter, the fundamental concept of digital watermarking, differences between visible and invisible watermarking, blind and non-blind watermark detection schemes, robust, fragile and semi-fragile watermarking algorithms, as well as four important properties for digital watermarking: imperceptibility, robustness, capacity and security will be described. A number of different transforms and algorithms used for robust image watermarking will be reviewed in detail. These include block based Discrete Cosine Transform (DCT), non-block based Discrete Wavelet Transform (DWT) and other state-of-the-art watermarking algorithms operating in the transform domain.