Papers by Alessandro Piva
IEEE Transactions on Information Forensics and Security, 2013
IEEE Signal Processing Magazine, 2005
The application of science and engineering to the analysis of priceless paintings and statues dat... more The application of science and engineering to the analysis of priceless paintings and statues dates back several centuries. However, only over the past few decades have analytical methods developed in the physical sciences been able to glean information, from the past and contribute to the analysis, conservation, and dissemination of works of art. By specifically focusing on the visual arts (e.g., on the binomial image processing and paintings), it is the purpose of this column to: 1) sketch the main applications that could benefit from the introduction of ad hoc image processing tools, 2) outline the state-of-the-art, 3) describe the main peculiarities of this field, and 4) discuss the main obstacles impeding a more fruitful cooperation between the image processing community and art historians, restorers, and artists in general.
ABSTRACT In this paper, a new watermarking system for copyright protection of digital images is p... more ABSTRACT In this paper, a new watermarking system for copyright protection of digital images is presented. The method operates in the frequency domain, by embedding a pseudorandom sequence of real numbers in a selected set of DFT coefficients of the ...
For reliably protecting the rights of multimedia dataowners, digital watermarking techniques appe... more For reliably protecting the rights of multimedia dataowners, digital watermarking techniques appear to bethe best solution. A digital watermark is a code whichis hidden into the multimedia data for carrying informationregarding the copyright. In this paper the problemof the reliable identification of the watermark, in absenceof the original unmarked image, is addressed. An optimum(based on a MAP, Maximum A Posteriori
The problem of optimum watermark recovery in a non additive, non Gaussian framework is addressed.... more The problem of optimum watermark recovery in a non additive, non Gaussian framework is addressed. Watermark casting is carried out on the frequency domain according to an additive-multiplicative rule. The structure of the optimum decoder is derived based on statistical decision theory. The Neyman-Pearson criterion is used to minimize the probability of missing the watermark for a given false detection rate. Experimental results highlights the superiority of the novel detector scheme with respect to conventional correlation-based decoding.
Abstract The performance of syntax-based error detection in the framework of H. 263 video transmi... more Abstract The performance of syntax-based error detection in the framework of H. 263 video transmission is not sufficient to detect errors reliably, calling for the adoption of more effective error detection techniques. A new technique, based on data hiding concepts, is ...
Abstract In the last few years, digital watermarking has been proposed as a solution to the probl... more Abstract In the last few years, digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia data against unauthorized uses. In the field of image watermarking, research has been mainly focused on grey-scale image ...
Because of the increasing influence it has in image watermarkingapplications, the estimation of t... more Because of the increasing influence it has in image watermarkingapplications, the estimation of the distributionshape of full frame DCT coefficients is here addressed.Based on previous analyses on block-DCT, the coefficientsare first assumed to follow a Generalized Gaussiandistribution. The shape parameter is then evaluatedaccording to the maximum likelihood criterion appliedto a set of 170 natural images. The analysis hasbeen further validated by using the ?2test-of-fit...
IEEE Transactions on Circuits and Systems for Video Technology, 2002
Abstract In the field of image watermarking, research has been mainly focused on grayscale image ... more Abstract In the field of image watermarking, research has been mainly focused on grayscale image watermarking, whereas the extension to the color case is usually accomplished by marking the image luminance, or by processing each color channel separately. A DCT ...
So far digital watermarking has been indicated as the most feasible answer for multimedia copyrig... more So far digital watermarking has been indicated as the most feasible answer for multimedia copyright protection issues, though many problems, especially regarding aspects of robustness against geometrical attacks, have not been completely and adequately solved yet. Robustness against geometric manipulations has been dealt with by inserting, together with the watermark, a synchronization template to be used later in the detection phase, to determine if a geometric distortion occurred and invert it before looking for the mark. A novel technique is presented, which, by exploiting the theory of geometric invariants, inserts a watermark intrinsically resistant to this sort of manipulations, thus avoiding the need of a synchronization pattern. Preliminary experimental results proving the goodness of the methodology are discussed along with some implementation problems due to the computational complexity.
IEEE Transactions on Image Processing, 2001
A watermarking algorithm operating in the wavelet domain is presented. Performance improvement wi... more A watermarking algorithm operating in the wavelet domain is presented. Performance improvement with respect to existing algorithms is obtained by means of a new approach to mask the watermark according to the characteristics of the human visual system (HVS). In contrast to conventional methods operating in the wavelet domain, masking is accomplished pixel by pixel by taking into account the texture and the luminance content of all the image subbands. The watermark consists of a pseudorandom sequence which is adaptively added to the largest detail bands. As usual, the watermark is detected by computing the correlation between the watermarked coefficients and the watermarking code, anyway the detection threshold is chosen in such a way that the knowledge of the watermark energy used in the embedding phase is not needed, thus permitting to adapt it to the image at hand.
IEEE Transactions on Image Processing, 2000
The evaluation of the number of bits that can be hidden within an image through digital watermark... more The evaluation of the number of bits that can be hidden within an image through digital watermarking is a crucial topic, which has been addressed only for additive watermarks. The evaluation of watermark capacity is very important because it allows to put a theoretical upper bound on the amount of information that can be hidden into an image by a given watermarking procedure, regardless of the watermark extraction technique. It is the purpose of this work to suggest a methodology for the evaluation of the watermark capacity in a nonadditive, non-Gaussian framework, and to discuss the results we obtained by applying it to a set of standard images
Image and Vision Computing, 1998
Signal Processing, 1998
Digital watermarking has been proposed as a solution to the problem of copyright protection of mu... more Digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia data in a networked environment. It makes possible to tightly associate to a digital document a code allowing the identification of the data creator, owner, authorized consumer, and so on. In this paper a new watermarking algorithm for digital images is presented: the method, which operates in the frequency domain, embeds a pseudo-random sequence of real numbers in a selected set of DCT coefficients. After embedding, the watermark is adapted to the image by exploiting the masking characteristics of the human visual system, thus ensuring the watermark invisibility. By exploiting the statistical properties of the embedded sequence, the mark can be reliably extracted without resorting to the original uncorrupted image. Experimental results demonstrate that the watermark is robust to several signal processing techniques, including JPEG compression, low pass and median filtering, histogram equalization and stretching, dithering, addition of Gaussian noise, resizing, and multiple watermarking.
The interest for image watermarking techniques has rapidly grown during recent years. Two require... more The interest for image watermarking techniques has rapidly grown during recent years. Two requirements are needed to be satis ed to use watermarking techniques for copyright protection: unperceivability and robustness against image processing algorithms and forgery attacks. In particular, it is widely accepted that the exploitation of the characteristics of the Human Visual System should greatly help for satisfying both these requirements. In this paper some solutions to the problem of building some perceptual masks for better hiding watermarks embedded in the full-frame DCT domain are preented. The results support the validity of the approach.
The growth of the Internet and the diffusion of multimedia applications requires the development ... more The growth of the Internet and the diffusion of multimedia applications requires the development of techniques for embedding identification codes into images, in such a way that it can be granted their authenticity and/or protected the copyright. In this paper a novel system for image watermarking, which exploits the similarity exhibited by the Digital Wavelet Transform with respect to the models of the Human Visual System, for robustly hiding watermarks is presented. In particular, a model for estimating the sensitivity of the eye to noise, previously proposed for compression applications, is used to adapt the watermark strength to the local content of the image. Experimental results are shown supporting the validity of the approach.
Digital watermarking has been proposed as a viable solution to the need of copyright protection a... more Digital watermarking has been proposed as a viable solution to the need of copyright protection and authentication of multimedia data in a networked environment, since it makes possible to identify the author, owner, distributor or authorized consumer of a document. In this paper a new watermarking technique to add a code to digital images is presented: the method operates in the frequency domain embedding a pseudo-random sequence of real numbers in a selected set of DCT coefficients. Watermark casting is performed by exploiting the masking characteristics of the Human Visual System, to ensure watermark invisibility. The embedded sequence is extracted without resorting to the original image, so that the proposed technique represents a major improvement to methods relying on the comparison between the watermarked and original images. Experimental results demonstrate that the watermark is robust to most of the signal processing techniques and geometric distortions.
IEEE Transactions on Signal Processing, 2003
This work addresses the problem of optimum decoding and detection of a multibit, multiplicative w... more This work addresses the problem of optimum decoding and detection of a multibit, multiplicative watermark hosted by Weibull-distributed features: a situation which is classically encountered for image watermarking in the magnitude-of-DFT domain. As such, this work can be seen as an extension of the system described in a previous paper, where the same problem is addressed for the case of 1-bit watermarking. The theoretical analysis is validated through Monte Carlo simulations. Although the structure of the optimum decoder/detector is derived in the absence of attacks, some experimental results are also presented, giving a measure of the overall robustness of the watermark when attacks are present.
IEEE Transactions on Image Processing, 2001
Watermark detection, i.e., the detection of an invisible signal hidden within an image for copyri... more Watermark detection, i.e., the detection of an invisible signal hidden within an image for copyright protection or data authentication, has classically been tackled by means of correlation-based techniques. Nevertheless, when watermark embedding does not obey an additive rule, or when the features the watermark is superimposed on do not follow a Gaussian pdf, correlation-based decoding is not the optimum choice. A new decoding algorithm is presented here which is optimum for nonadditive watermarks embedded in the magnitude of a set of full-frame DFT coefficients of the host image. By relying on statistical decision theory, the structure of the optimum decoder is derived according to the Neyman-Pearson criterion, thus permitting to minimize the missed detection probability subject to a given false detection rate. The validity of the optimum decoder has been tested thoroughly to assess the improvement it permits to achieve from a robustness perspective. The results we obtained confirm the superiority of the novel algorithm with respect to classical correlation-based decoding.
... Alessandro Piva, Roberto Caldelli, Alessia De Rosa ... Detection results are shown in Figure ... more ... Alessandro Piva, Roberto Caldelli, Alessia De Rosa ... Detection results are shown in Figure 2 (a) for VO 0, and (b) for VO 1: the response of the wa-termark detector to 200 marks randomly generated shows that the response to the embedded watermark sequence (ie no. ...
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Papers by Alessandro Piva