Jeffrey J. Rodriguez

Expansion Embedding Techniques for Reversible Watermarking

Reversible watermarking enables the embedding of useful information in a host signal without any loss of host information. Tians difference-expansion technique is a high-capacity, reversible method for data embedding. However, the method suffers from undesirable distortion at low embedding capacities and lack of capacity control due to the need for embedding a location map. We propose a histogram shifting technique as an alternative to embedding the location map. The proposed technique improves the distortion performance at low embedding capacities and mitigates the capacity control problem. We also propose a reversible data-embedding technique called prediction-error expansion. This new technique better exploits the correlation inherent in the neighborhood of a pixel than the difference-expansion scheme. Prediction-error expansion and histogram shifting combine to form an effective method for data embedding. The experimental results for many standard test images show that prediction-error expansion doubles the maximum embedding capacity when compared to difference expansion. There is also a significant improvement in the quality of the watermarked image, especially at moderate embedding capacities

Texture analysis of optical coherence tomography images: feasibility for tissue classification

Optical coherence tomography (OCT) acquires cross-sectional images of tissue by measuring back-reflected light. Images from in vivo OCT systems typically have a resolution of 10 to 15 mm, and are thus best suited for visualizing structures in the range of tens to hundreds of microns, such as tissue layers or glands. Many normal and abnormal tissues lack visible structures in this size range, so it may appear that OCT is unsuitable for identification of these tissues. However, examination of structure-poor OCT images reveals that they frequently display a characteristic texture that is due to speckle. We evaluated the application of statistical and spectral texture analysis techniques for differentiating tissue types based on the structural and speckle content in OCT images. Excellent correct classification rates were obtained when images had slight visual differences (mouse skin and fat, correct classification rates of 98.5 and 97.3%, respectively), and reasonable rates were obtained with nearly identical-appearing images (normal versus abnormal mouse lung, correct classification rates of 64.0 and 88.6%, respectively). This study shows that texture analysis of OCT images may be capable of differentiating tissue types without reliance on visible structures.

Prediction-error based reversible watermarking

Reversible watermarking has become a highly desirable subset of fragile watermarking for sensitive digital imagery in application domains such as military and medical because of the ability to embed data with zero loss of host information. This reversibility enables the recovery of the original host content upon verification of the authenticity of the received content. We propose a new reversible watermarking algorithm. The algorithm exploits the correlation inherent among the neighboring pixels in an image region using a predictor. The prediction-error at each location is calculated and, depending on the amount of information to be embedded, locations are selected for embedding. Data embedding is done by expanding the prediction-error values. A compressed location map of the embedded locations is also embedded along with the information bits. Our algorithm exploits the redundancy in the image to achieve very high data embedding rates while keeping the resulting distortion low.

Stochastic analysis of stereo quantization error

The probability density function of the range estimation error and the expected value of the range error magnitude are derived in terms of the various design parameters of a stereo imaging system. In addition, the relative range error is proposed as a better way of quantifying the range resolution of a stereo imaging system than the percent range error when the depths in the scene lie within a narrow range. >

Matching aerial images to 3-D terrain maps

A terrain-matching algorithm is presented for use in a passive aircraft navigation system. A sequence of aerial images is matched to a reference digital map of the 3-D terrain. Stereo analysis of successive images results in a recovered elevation map. A cliff map is then used as a novel compact representation of the 3-D surfaces. The position and heading of the aircraft are determined with a terrain-matching algorithm that locates the unknown cliff map within the reference cliff map. The robustness of the matching algorithm is demonstrated by experimental results using real terrain data. >

Reversible watermarking by prediction-error expansion

We propose a new reversible (lossless) watermarking algorithm for digital images. Being reversible, the algorithm enables the recovery of the original host information upon the extraction of the embedded information. The proposed technique exploits the inherent correlation among the adjacent pixels in an image region using a predictor. The information bits are embedded into the prediction errors, which enables us to embed a large payload while keeping the distortion low. A histogram shift at the encoder enables the decoder to identify the embedded location.

Color image enhancement using spatially adaptive saturation feedback

One way of enhancing color image contrast is to feed back high-frequency spatial information from the saturation component into the luminance component. A new algorithm, which uses a spatially variant measure of salience, is presented. This method offers key improvements to a previous saturation feedback technique. Experimental results confirm that improved color image enhancement is achieved.

IP protection for VLSI designs via watermarking of routes

Intellectual property protection (IPP) has become a major concern in todays CAD and ASIC/SOC industries. This paper presents a watermarking technique for IPP at the physical design level. We propose a method for embedding a watermark by modifying the number of vias or bends used to route the nets in a design. This technique is applicable to digital, analog and mixed-signal design, and has the ability to accommodate the noise tolerance and design intricacies of each.

Computer-aided identification of ovarian cancer in confocal microendoscope images.

The confocal microendoscope is an instrument for imaging the surface of the human ovary. Images taken with this instrument from normal and diseased tissue show significant differences in cellular distribution. A real-time computer-aided system to facilitate the identification of ovarian cancer is introduced. The cellular-level structure present in ex vivo confocal microendoscope images is modeled as texture. Features are extracted based on first-order statistics, spatial gray-level-dependence matrices, and spatial-frequency content. Selection of the features is performed using stepwise discriminant analysis, forward sequential search, a nonparametric method, principal component analysis, and a heuristic technique that combines the results of these other methods. The selected features are used for classification, and the performance of various machine classifiers is compared by analyzing areas under their receiver operating characteristic curves. The machine classifiers studied included linear discriminant analysis, quadratic discriminant analysis, and the k-nearest-neighbor algorithm. The results suggest it is possible to automatically identify pathology based on texture features extracted from confocal microendoscope images and that the machine performance is superior to that of a human observer.

Quantization error in stereo imaging

In the design of a stereo imaging system, one often chooses the parameters to meet a desired error level. The probability density function of the range estimation error and the expected value of the range error magnitude are derived in terms of the various design parameters. The relative range error is proposed as a better way of quantifying the range resolution of a stereo imaging system.<<ETX>>