摘要:

Markov random field models and Bayesian methods have provided answers to various contemporary problems in Image Analysis. We give a very brief introduction to the topic. In particular, we highlight the use of Bayesian methods in classifying the image into different classes.

ISSN:0266-4763    

DOI:10.1080/02664768900000013

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

Image models are useful in quantitatively specifying natural constraints and general assumptions about the physical world and the imaging process. This review paper explains how Gibbs and Markov random field models provide a unifying theme for many contemporary problems in image analysis. Random field models permit the introduction of spatial context into pixel labeling problems, such as segmentation and restoration. Random field models also describe textured images and lead to algorithms for generating textured images, classifying textures, and segmenting textured images. In spite of some impressive model-based image restoration and texture segmentation results reported in the literature, a number of fundamental issues remain unexplored, such as the specification of MRF models, modeling noise processes, performance evaluation, parameter estimation, the phase transition phenomenon, and the comparative analysis of alternative procedures. The literature of random field models is filled with great promise, but a better mathematical understanding of these issues is needed as well as efficient algorithms for applications. These issues need to be resolved before random field models will be widely accepted as general tools in the image processing community.

ISSN:0266-4763    

DOI:10.1080/02664768900000014

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

A technique is presented for enhancing and combining electron microscope images of small clystalline areas. Phases obtained by Fourier transforming electron micrographs are merged with available more precise amplitudes, in a Fourier synthesis, to obtain a final estimated image. The procedure is illustrated with 42 individual images of the purple membrane from Halobacterium halobium. To show the power of combination, results based on 1, 2, 4, 8, 16, 32 and 42 images are presented. An estimate based solely on the micrograph data, i.e. ignoring the precise amplitudes, is also presented and is seen to be notably poorer. The level of uncertainty of the final image is assessed by stimulating 10 final images and superposing the results.

ISSN:0266-4763    

DOI:10.1080/02664768900000015

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

Positron emission tomography (PET) is an important medical imaging technique. Statistically, the PET image reconstruction problem comprises estimating the intensity function of a non-homogeneous Poisson process from a set of indirectly observed data (an integral transform is involved). In this paper, we investigate a new reconstruction method consisting in the adaptation of orthogonal series density estimation techniques to use with an idealised form of the PET problem. The method provides reasonable reconstructions quickly; its computational speed is its major advantage. It has further advantages (e.g. no pixellation required) and various disadvantages (e.g. difficulties with object boundaries, non-negativity not guaranteed) which are discussed. Its major disadvantage, however, is the difficulty associated with generalising the approach to cope with more realistic versions of the PET model.

ISSN:0266-4763    

DOI:10.1080/02664768900000016

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

Optical astronomers now normally collect digital images by means of CCD detectors, which are blurred by atmospheric motion and distorted by physical noise in the detection process. We examine Bayesian procedures to clean such images using explicit models from spatial statistics for the underlying structure, and compare these methods with those based on maximum entropy.

ISSN:0266-4763    

DOI:10.1080/02664768900000017

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

ISSN:0266-4763    

DOI:10.1080/02664768900000018

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

We introduce a class of small scale simulation models—‘prototypes'—which reproduce many of the known properties of maximum likelihood and related reconstruction methods used in emission tomography, and greatly simplify the development of new methods. We introduce an iterative Fisher-scoring algorithm and demonstrate, by use of the prototype models, its superior speed of convergence when compared with the standard EM algorithm.

ISSN:0266-4763    

DOI:10.1080/02664768900000019

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

Image restoration, image smoothing, and probability law estimation are important inverse problems in optics. Within the past 10 or so years, much progress has been made toward their resolution. These problems are often ill-posed mathematically. However, such concepts as maximum entropy, maximum likelihood, binay decision discrimination, median window filtering, MAP estimation, and minimum Fisher information have proven invaluable in regularising, or reducing, the ill-posed nature of the problems. In particular, those concepts which measure uncertainty or disorder have played a central role. Given noise-prone data, concepts that describe maximal disorder (maximum entropy, minimum Fisher information, minimal bina y discrimination) exert a smoothing influence on the solutions that drastically reduces noise propagation into the output. Given insufficient but noise-free data, as in the probability estimation problem, the principle of minimum Fisher information, in particular, creates smooth estimates which, oftentimes, are physically correct as well.

ISSN:0266-4763    

DOI:10.1080/02664768900000020

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

The paper investigates parameter estimation for Markov random fields and for hidden Markov random fields, where noisy data are available. EM algorithms are described and an approximate procedure is developed based on row-by-row relaxation and analysis. Numerical illustrations are provided.

ISSN:0266-4763    

DOI:10.1080/02664768900000021

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor

摘要:

When considering the problem of the classification of satellite data, several authors have shown the superiority of the contextual method over the blind (pixel by pixel) method. Determining the discriminating functions which define the best contextual strategy (in the Bayesian sense) requires knowledge of the distribution of the restriction of the random field which models the picture, to the given context. We propose an estimator of this distribution and demonstrate its good asymptotic behaviour in very weak hypotheses.

ISSN:0266-4763    

DOI:10.1080/02664768900000022

出版商:Carfax Publishing Company    

年代:1989

数据来源: Taylor