448363
A multiscale error diffusion technique for digital halftoning
A new digital halftoning technique based on multiscale error diffusion is examined. We use an image quadtree to represent the difference image between the input gray-level image and the output halftone image. In iterative algorithm is developed that searches the brightest region of a given image via "maximum intensity guidance" for assigning dots and diffuses the quantization error noncausally at each iteration. To measure the quality of halftone images, we adopt a new criterion based on hierarchical intensity distribution. The proposed method provides very good results both visually and in terms of the hierarchical intensity quality measure.
1584599
Embedded coding of 3D graphic models
A progressive compression method which encodes a 3D graphic models into an embedded bit stream is investigated. The coder first encodes the coarsest resolution of the model, and then includes the information of finer details gradually. A rate-distortion model is used in the integration of different types of bit streams into a single embedded bit stream to optimize the overall coding performance. This embedding property can be applied to progressive transmission, multi-resolution editing and level-of-detail control. Numerical experiments are provided to demonstrate the excellent rate-distortion performance of the proposed method.
12508411
Texture analysis and classification with tree-structured wavelet transform
A multiresolution approach based on a modified wavelet transform called the tree-structured wavelet transform or wavelet packets is proposed. The development of this transform is motivated by the observation that a large class of natural textures can be modeled as quasi-periodic signals whose dominant frequencies are located in the middle frequency channels. With the transform, it is possible to zoom into any desired frequency channels for further decomposition. In contrast, the conventional pyramid-structured wavelet transform performs further decomposition in low-frequency channels. A progressive texture classification algorithm which is not only computationally attractive but also has excellent performance is developed. The performance of the present method is compared with that of several other methods.
5323044
Recovery of multiband signals using finite samples
In this research, we consider a special class of band-limited signals which have a multiband structure in the frequency domain, and propose a new reconstruction algorithm to exploit the multiband feature of the underlying signals. The concept of the critical value is introduced to measure the performance of a reconstruction algorithm. We show analytically that the new algorithm performs better than the MMSE estimator for band-limited/multiband signals in terms of the critical value and region measure. Numerical examples are given for performance comparison of various methods.<<ETX>>
28495632
Iterative signal extrapolation algorithms with wavelets
A generalized Papoulis-Gerchberg (PG) algorithm for signal extrapolation based on the wavelet representation has been recently proposed by Xia, Kuo and Zhang. In this research, we first show that the generalized PG algorithm converges to the minimum norm solution when the wavelet bases are semi-orthogonal (or known as the prewavelet). However, the generalized PG algorithm converges slowly in numerical implementation. To accelerate the convergence rate, we formulate the discrete signal extrapolation problem os a two-step process and apply the steepest descent and conjugate gradient methods for its solution. Numerical experiments are given to illustrate the performance of the proposed algorithms.<<ETX>>
14807272
Progressive compression of 3D graphic models
A progressive coding method which encodes a 3D graphic model into an embedded bit stream is investigated in this research. The coder first encodes the coarsest resolution of the model, and then includes the finer details gradually. The embedding property allows the decoder to terminate the decoding at an arbitrary position in the compressed bit stream, and a more accurate model can be obtained when more bits are decoded. Numerical experiments are provided to demonstrate the excellent rate distortion performance and progressive compression performance of the new method.
12709015
Motion-compensated frame interpolation scheme for H.263 codec
A fast block-based motion-compensated frame interpolation (FMCI) scheme was proposed in our previous work. FMCI does not require any motion search in the decoder so that the complexity is low enough to achieve frame rate increase in real time. To further improve the visual quality, we propose two add-on schemes to enhance FMCI in this research. They are the adaptive frame skip (AFS) scheme applied at the encoder and the hybrid frame interpolation (HFI) scheme which incorporates both frame repetition and FMCI at the decoder. By adopting these two add-on features, the enhanced FMCI method is made more robust to allow smooth playback.
12549772
Designing an evaluation method for security user interfaces: lessons from studying secure wireless network configuration
: / 28 Ten or 20 years ago, evaluating security products was not as much of a problem as it is today. Systems were managed by people able—and willing—to master the complexities. However, with the proliferation of personal computing devices and network connectivity in the home, systems are now regularly managed by nonexperts. Each system needs to be secured by each user in each home. Therefore designing effective, unbiased evaluation methods for consumer products is one of the first steps in improving both users’ experiences and their security practices. Evaluating the usability of security is a challenge. A common question evaluators face is: “How do I test whether users will configure and use a product securely?” In this article, we outline problems we encountered in evaluating secure wireless network configuration and examine the assumptions many user study methods make, but which may not hold for security.