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We propose a robust quantization-based image watermarking scheme, called the gradient direction watermarking (GDWM), based on the uniform quantization of the direction of gradient vectors. In GDWM, the watermark bits are embedded by quantizing the angles of significant gradient vectors at multiple wavelet scales. The proposed scheme has the following(More)
Gradient estimators are mostly designed to yield accurate and robust estimates of the gradient magnitude, not the gradient direction. This paper proposes a method for the accurate and robust estimation of both the gradient magnitude and direction. It robustly estimates the gradient in the <i>x</i>- and <i>y</i>-directions. The robustness against noise is(More)
—A successful approach to image quality assessment involves comparing the structural information between a distorted and its reference image. However, extracting structural information that is perceptually important to our visual system is a challenging task. This paper addresses this issue by employing a sparse representation-based approach and proposes a(More)
An improved blind image quality assessment scheme that is based on the Watson's just noticeable difference (JND) modulated spread spectrum watermarking, is proposed. For the purpose of quality monitoring, a watermark is embedded into the original image. The image quality is estimated based on the detected watermark at the receiver side. In terms of the peak(More)
Many successful image quality metrics rely on the structural information in an image to assess its perceptual quality. Extracting the structural information that is perceptually meaningful to our visual system, however, is a challenging task. This paper proposes a new quality assessment metric that relies on a sparse modeling approach to learn the inherent(More)
This paper presents the new concept of watermark survival chance (WSC) for improving watermark robustness. WSC provides a robustness measure for an image feature (e.g. a discrete wavelet transform (DWT) coefficient) when used for watermark embedding, and thus can provide the watermark designer with prior knowledge on robust image features. As an(More)
A robust data hiding scheme that embeds the watermark bits by quantizing the gradient directions of an image is proposed. By embedding the watermark in the angle, the watermark becomes robust to amplitude scaling attacks. To keep the watermark imperceptible and enhance its robustness, it is embedded in the significant gradient vectors of the image. The(More)
A new vector-wise scheme for the gradient estimation and edge detection in noisy color images is proposed. In color images, different types of noise may corrupt the image. To reduce the effects of noise in the gradient estimation, we introduce the RCMG-Median- Mean estimator. RCMG-Median-Mean is a combination of the robust color morphological gradient(More)
This paper presents a fuzzy approach for contrast enhancement, based on two multi-scale transforms, namely wavelet and contourlet transforms. Separability and nondirectionality of conventional 2D wavelet transform, makes it unsuitable for sparsely representation of curve or line shaped image objects. On the other hand, the contourlet transform isa good(More)