Zensho Nakao

Robust multi-logo watermarking by RDWT and ICA

This paper proposes a new approach to watermarking multimedia products by redundant discrete wavelet transform (RDWT) and independent component analysis (ICA). For watermark security, embedded logo watermarks are encrypted to random noise signal. To embed logo watermarks, the original image is decomposed by RDWT, and watermarks are embedded into middle frequency at LH and HL sub-bands. The perceptual model is applied with a stochastic multiresolution model for adaptive watermark embedding. This is based on computation of a noise visibility function (NVF) which has local image properties. We also propose an intelligent ICA-based detector which directly extracts watermarks in spatial domain. A novel characteristic of this detection is that it does not require the transformation process to extract the watermark. The experimental results show that logo watermarks are extracted perfectly, and also demonstrate the robustness of the method.

Texture representation based on pattern map

We propose a pixel-pattern-based texture feature (PPBTF) which is insensitive to variance of illumination. A gray scale image is transformed into a pattern map where edges and lines (bars) to be used for characterizing the texture information are classified by pattern matching. Based on the pattern map, a feature vector is comprised of the numbers of the pixels belonging to each pattern. We use the image basis functions obtained by principal component analysis as the templates for pattern matching. The characteristics of the feature is comprehensively analyzed through an application to texture image segmentation. Comparisons with multichannel filtering methods show that PPBTF feature is quite time saving and free of the influence of illumination.

ROBUST DIGITAL WATERMARKING BASED ON PRINCIPAL COMPONENT ANALYSIS

We propose a robust digital watermarking technique based on Principal Component Analysis (PCA) and evaluate the effectiveness of the method against some watermark attacks. In this proposed method, watermarks are embedded in the PCA domain and the method is closely related to DCT or DWT based frequency-domain watermarking. The orthogonal basis functions, however, are determined by data and they are adaptive to the data. The presented technique has been successfully evaluated and compared with DCT and DWT based watermarking methods. Experimental results show robust performance of the PCA based method against most prominent attacks.

Restoration of gray images based on a genetic algorithm with Laplacian constraint

Genetic algorithms are used for restoration of gray images. The restoration problem is modeled as an optimization problem, whose cost function is minimized based on mechanics of natural selection and natural genetics. Because the complicated a priori constraints can be easily incorporated by the appropriate modification of the cost function, the algorithm is well suited to the solution of ill-posed problem. The possibility has been demonstrated with computer simulations. A parallel implementation on a multi-workstation environment has been implemented.

Curvelet-Domain Image Watermarking Based on Edge-Embedding

A new curvelet-based watermarking technique is presented in this paper, in which watermark signals are selected to be a gray-scale logo image. The curvelet transform was developed in order to represent edges along curves much more efficiently than the traditional transforms. We apply the transform to watermarking and evaluate the effectiveness of the method. Our watermarking algorithm embeds a watermark in curvelet coefficients which are selected by a criterion whether they contain as much edge information as possible. We evaluated the effectiveness of the method against some watermark attacks. Experiment results show that our new method yields quite good visual quality in watermarked images, and is robust to typical signal processing attacks such as compression, cropping, adding noise and filtering.

A heuristic penumbral imaging technique for measurements of laser-produced plasma density profile

Penumbral imaging is a powerful technique for imaging of penetrating radiations such as neutrons and hard x ray with a high spatial resolution. Recently, the technique has also been used for measurement of laser-produced plasma density profile. The limitation is that the straightforward image or signal reconstruction will introduce a significant distortion if the penumbral image is distorted by the noise. In this article, we propose a heuristic method for reconstruction of penumbral images. Both simulation and experimental results demonstrated that the proposed method is robust and tolerant to the noise.

Color Image Watermarking and Self-recovery Based on Independent Component Analysis

The digital image watermarking field addresses the problem of digital image authentication and integrity. In this paper we propose a novel color image watermarking scheme based on image self-embedding and self-recovery techniques. The main idea of this algorithm is to embed a reduced content of the original image to itself, in order to be able to partially recover the deleted features from the watermarked image. Separately, the red and blue color channels are embedded, respectively in the wavelet domain by a compressed version of the original image, and in the spatial domain by binary encoded sequences generated from the original image. This allowed us, in detection stage, to prove the ownership, detect the altered blocks, and recover them. The detection and recovery bits extraction is computed using an ICA algorithm. The experimental results were satisfactory and show a high robustness against most common attacks as well as a reassuring rate of image recovery.

Evolutionary computation for topological optimization of 3-connected computer networks

In the 3-connected computer network design problem, a set of links is to be assigned to some computer sites (nodes) such that every source-destination pair of nodes can successfully communicate with each other via at least one of three diverse paths. The objective is to minimize the total link connection costs while maintaining the 3-connectivity constraint. We develop two heuristics, a greedy heuristic and a genetic algorithm (GA) based heuristic to approximately solve the design problem. An experimental evaluation shows that the GA consistently outperforms the greedy algorithm for the problem instances considered.

PCA Based Digital Watermarking

This work evaluates a novel watermarking method based on Principle Component Analysis and effectiveness of the method to some watermark attacks. A PCA is used on a block by block basis to decorrelate the image pixel, watermarks are added in the Principle Components of an image. A theoretical description of the method is included together with experimental results in order to validate the methodology presented. Simulation shows the performance of the method to be robust for image cropping and some attacks such as additive noise, low pass filtering, median filtering, and jpeg compression. This research presents a new approach to watermarking fields with good performance in image cropping, and enhancement to this system with respect to robustness against various attacks is under investigation.

Blind reconstruction of x-ray penumbral images based on a heuristic method

We apply a heuristic method to blind reconstruction of noisy penumbral images. Penumbral imaging is a powerful technique for imaging with penetrating radiation such as neutrons and hard x ray with a high spatial resolution. Limitations of the conventional reconstruction method are that it will introduce a significant distortion if the penumbral image is distorted by the noise, and that the point spread function (PSF) must be exactly known beforehand. The proposed method can estimate both the source image and the diameter of the PSF from only the penumbral image. The efficacy of the method is demonstrated by computer simulation and real laser plasma experiments.