Edward J. Delp

Perceptual watermarks for digital images and video

The growth of new imaging technologies has created a need for techniques that can be used for copyright protection of digital images and video. One approach for copyright protection is to introduce an invisible signal, known as a digital watermark, into an image or video sequence. In this paper, we describe digital watermarking techniques, known as perceptually based watermarks, that are designed to exploit aspects of the the human visual system in order to provide a transparent (invisible), yet robust watermark. In the most general sense, any watermarking technique that attempts to incorporate an invisible mark into an image is perceptually based. However, in order to provide transparency and robustness to attack, two conflicting requirements from a signal processing perspective, more sophisticated use of perceptual information in the watermarking process is required. We describe watermarking techniques ranging from simple schemes which incorporate common-sense rules in using perceptual information in the watermarking process, to more elaborate schemes which adapt to local image characteristics based on more formal perceptual models. This review is not meant to be exhaustive; its aim is to provide the reader with an understanding of how the techniques have been evolving as the requirements and applications become better defined.

Digital watermarking: algorithms and applications

Digital watermarking of multimedia content has become a very active research area over the last several years. A general framework for watermark embedding and detection/decoding is presented here along with a review of some of the algorithms for different media types described in the literature. We highlight some of the differences based on application such as copyright protection, authentication, tamper detection, and data hiding as well as differences in technology and system requirements for different media types such as digital images, video, audio and text.

A watermark for digital images

The growth of networked multimedia systems has magnified the need for image copyright protection. One approach used to address this problem is to add an invisible structure to an image that can be used to seal or mark it. These structures are known as digital watermarks. We describe two techniques for the invisible marking of images. We analyze the robustness of the watermarks with respect to linear and nonlinear filtering, and JPEG compression. The results show that our watermarks detect all but the most minute changes to the image.

An iterative growing and pruning algorithm for classification tree design

A critical issue in classification tree design-obtaining right-sized trees, i.e. trees which neither underfit nor overfit the data-is addressed. Instead of stopping rules to halt partitioning, the approach of growing a large tree with pure terminal nodes and selectively pruning it back is used. A new efficient iterative method is proposed to grow and prune classification trees. This method divides the data sample into two subsets and iteratively grows a tree with one subset and prunes it with the other subset, successively interchanging the roles of the two subsets. The convergence and other properties of the algorithm are established. Theoretical and practical considerations suggest that the iterative free growing and pruning algorithm should perform better and require less computation than other widely used tree growing and pruning algorithms. Numerical results on a waveform recognition problem are presented to support this view. >

The Use of Mobile Devices in Aiding Dietary Assessment and Evaluation

There is a growing concern about chronic diseases and other health problems related to diet including obesity and cancer. The need to accurately measure diet (what foods a person consumes) becomes imperative. Dietary intake provides valuable insights for mounting intervention programs for prevention of chronic diseases. Measuring accurate dietary intake is considered to be an open research problem in the nutrition and health fields. In this paper, we describe a novel mobile telephone food record that will provide an accurate account of daily food and nutrient intake. Our approach includes the use of image analysis tools for identification and quantification of food that is consumed at a meal. Images obtained before and after foods are eaten are used to estimate the amount and type of food consumed. The mobile device provides a unique vehicle for collecting dietary information that reduces the burden on respondents that are obtained using more classical approaches for dietary assessment. We describe our approach to image analysis that includes the segmentation of food items, features used to identify foods, a method for automatic portion estimation, and our overall system architecture for collecting the food intake information.

Use of technology in children’s dietary assessment

Background:Information on dietary intake provides some of the most valuable insights for mounting intervention programmes for the prevention of chronic diseases. With the growing concern about adolescent overweight, the need to accurately measure diet becomes imperative. Assessment among adolescents is problematic as this group has irregular eating patterns and they have less enthusiasm for recording food intake.Subjects/Methods:We used qualitative and quantitative techniques among adolescents to assess their preferences for dietary assessment methods.Results:Dietary assessment methods using technology, for example, a personal digital assistant (PDA) or a disposable camera, were preferred over the pen and paper food record.Conclusions:There was a strong preference for using methods that incorporate technology such as capturing images of food. This suggests that for adolescents, dietary methods that incorporate technology may improve cooperation and accuracy. Current computing technology includes higher resolution images, improved memory capacity and faster processors that allow small mobile devices to process information not previously possible. Our goal is to develop, implement and evaluate a mobile device (for example, PDA, mobile phone) food record that will translate to an accurate account of daily food and nutrient intake among adolescents. This mobile computing device will include digital images, a nutrient database and image analysis for identification and quantification of food consumption. Mobile computing devices provide a unique vehicle for collecting dietary information that reduces the burden on record keepers. Images of food can be marked with a variety of input methods that link the item for image processing and analysis to estimate the amount of food. Images before and after the foods are eaten can estimate the amount of food consumed. The initial stages and potential of this project will be described.

Wavelet based rate scalable video compression

In this paper, we present a new wavelet based rate scalable video compression algorithm. We will refer to this new technique as the scalable adaptive motion compensated wavelet (SAMCoW) algorithm. SAMCoW uses motion compensation to reduce temporal redundancy. The prediction error frames and the intracoded frames are encoded using an approach similar to the embedded zerotree wavelet (EZW) coder. An adaptive motion compensation (AMC) scheme is described to address error propagation problems. We show that, using our AMC scheme, the quality of the decoded video can be maintained at various data rates. We also describe an EZW approach that exploits the interdependency between color components in the luminance/chrominance color space. We show that, in addition to providing a wide range of rate scalability, our encoder achieves comparable performance to the more traditional hybrid video coders, such as MPEG1 and H.263. Furthermore, our coding scheme allows the data rate to be dynamically changed during decoding, which is very appealing for network-oriented applications.

Optimum color spaces for skin detection

The objective of this paper is to show that for every color space there exists an optimum skin detector scheme such that the performance of all these skin detectors schemes is the same. To that end, a theoretical proof is provided and experiments are presented which show that the separability of the skin and no skin classes is independent of the color space chosen.

Impulsive noise suppression and background normalization of electrocardiogram signals using morphological operators

An approach to impulsive noise suppression and background normalization of digitized electrocardiogram signals using mathematical morphological operators that incorporate the shape information for a signal is presented. A brief introduction to these nonlinear signal processing operators, as well as a detailed description of the algorithm, is presented. Empirical results show that the algorithm has good performance in impulsive noise suppression and background normalization.<<ETX>>

On detecting dominant points

Abstract Detecting dominant points is a crucial preprocessing step for shape recognition and point-based motion estimation. Polygonal approximation has been a commonly used approach in detecting dominant points. This paper presents two alternatives which detect stable dominant points. In the first method, we find a set of positive maximum and negative minimum curvature points along the Gaussian smoothed boundary, followed by a split-and-merge polygonal approximation algorithm. The resulting break points, vertices of the approximated polygon, are the dominant points. Experimental results show that dominant points obtained by this method are less sensitive to the orientation of the boundary than other polygonal approximation algorithms in the sense that the number and the location of the dominant points along the contour remain relatively unchanged. In the second method, we smooth a boundary by a Gaussian filter using various widths until the extreme curvature points remain relatively unchanged for a range of filter widths. The resulting extreme curvature points which are stable to orientation and a reasonable range of scaling are the dominant points.