Elsevier

Pattern Recognition

Volume 53, May 2016, Pages 229-237
Pattern Recognition

The Kolmogorov–Sinai entropy in the setting of fuzzy sets for image texture analysis and classification

https://doi.org/10.1016/j.patcog.2015.12.012Get rights and content

Highlights

  • Development of a new method for feature extraction using chaos and fuzzy sets.

  • Modeling Kolmogorov–Sinai (K–S) entropy with fuzzy logic is feasible.

  • Fuzzy K–S entropy is an effective feature for analysis and classification of textural images.

Abstract

The Kolmogorov–Sinai (K–S) entropy is used to quantify the average amount of uncertainty of a dynamical system through a sequence of observations. Sequence probabilities therefore play a central role for the computation of the entropy rate to determine if the dynamical system under study is deterministically non-chaotic, deterministically chaotic, or random. This paper extends the notion of the K–S entropy to measure the entropy rate of imprecise systems using sequence membership grades, in which the underlying deterministic paradigm is replaced with the degree of fuzziness. While constructing sequential probabilities for the calculation of the K–S entropy is difficult in practice, the estimate of the K–S entropy in the setting of fuzzy sets in an image is feasible and can be useful for modeling uncertainty of pixel distributions in images. The fuzzy K–S entropy is illustrated as an effective feature for image analysis and texture classification.

Introduction

Texture is an important feature to describe an attribute of an image, which is a phenomenon existing in natural scenes, physical and biological appearances, and art work. Mathematical methods such as measures of smoothness, coarseness, and spatial regularity of distributions of pixels are often used to quantify and classify the texture content of different types of images. Although texture is inherently present in images, it is easy to recognize but difficult to define [1]. This is because texture is subject to human perception, and therefore there is no single precise mathematical definition of texture [2]. In general, there are three main approaches to the analysis of texture: statistical, structural, and spectral [3]. Statistical approaches characterize textures as smooth, coarse, grainy, and so on. Structural techniques deal with the arrangement of image primitives, such as the description of texture based on regularly spaced parallel lines. Spectral techniques are based on properties of the frequency content of an image to detect global periodicity by taking into account high-energy, narrow peaks in the spectrum. It is known that texture analysis has a long and rich development in image processing and computer vision [4], [5], [6], [7] as there is a textbook devoted to the topic of image texture [8]. In fact, the extraction of texture features continues receiving considerable attention to both technical developments [9], [10], [11], [12], [13], [14] and applications [15], [16], [17], [18], [19], [20].

It has been pointed out that texture analysis is difficult because of the lack of effective methods for characterizing texture at different scales and in terms of spatial multiresolution; therefore, techniques such as wavelet transform and Gabor filter can be useful for texture analysis [6], [21]. Although there are many developments of methods and their applications for texture analysis, the challenge of the classification of texture in images still remains. This is because the properties of texture are ill-defined and complex in nature, being due to the high degree of local spatial variations of image intensity in orientation and scale. Such complexity makes it a burdensome task for current mathematical models to effectively discriminate various types of textural information.

As a matter of fact, information and uncertainty are a coupled entity that exists and needs to be addressed in many complex problems of pattern recognition [22]. It is the uncertainty in information, which makes real-life patterns be both predictable and unpredictable at once. For example, in performance art, we know the pianist will play all the notes that Beethoven wrote, but the performance seems like it can go anywhere spontaneously. This is known as “the uncertainty principle and pattern recognition” [23]. A major school of thought for quantifying the predictability or uncertainty in complex information processing is the theory of chaos and nonlinear dynamics. Chaos is the study of surprises, the nonlinear and the unpredictable; while traditional science deals with supposedly predictable phenomena. In spite of its wide applications in many fields of science and engineering, techniques developed for measuring nonlinear behavior in chaotic signals are mainly concerned with time-series data. Little effort has been spent on the formulation and extension of chaos analysis for quantifying the unpredictability of the nature of texture.

The study presented in this paper was motivated by the utilization of the theories of chaos and fuzzy sets for addressing dynamic uncertainty to characterize the spatial arrangement of the distribution of intensities in textural images. In fact, it has been pointed out that the theory of chaos and fuzzy logic are among the most interesting fields of mathematical research, and these two theories were applied to study the semantic dynamics of self-reference [24]. The rest of this paper is organized as follows. Section 2 briefly describes the concept of the Kolmogorov–Sinai (K–S) entropy. The notion of the fuzzy K–S entropy is introduced in Section 3. Section 4 presents the estimate of the fuzzy K–S entropy in images. Experimental results on different types of textural images and benchmark data are discussed in Section 5. Finally, Section 6 is the conclusion of the research findings.

Section snippets

K–S entropy

The theory of chaos and the notion of entropy measure in information theory have been found useful for solving various problems in complex systems [25], [26], [27], ranging from electromagnetic transmission of information to medicine and biology [28], [29], [30]. The three most well-known quantitative measures of chaos are the Lyapunov exponents, Kolmogorov–Sinai (K–S) entropy, and mutual information [31], [32]. This paper particularly focuses on the K–S entropy [33] to extend its notion to

K–S entropy of fuzzy sets

Let X={x} be a collection of points. A fuzzy set A in X is defined as a set of ordered pairs: A={(x,μA(x))|xX}, where μA(x) is called the fuzzy membership function for the fuzzy set A, which maps each element of X to a real number in the interval [0, 1] [38]. The entropy of the fuzzy set A, denoted by D(A), is a measure of the degree of its fuzziness, which has the following three properties [39]:

  • 1.

    D(A)=0 if A is a crisp (non-fuzzy) set, that is, if μA(x){0,1}x;

  • 2.

    D(A) is maximum μA(x)=0.5 (most

K–S entropy of fuzzy information in images

This section develops a model for estimating the K–S entropy of fuzzy information in images. In fact, image properties are not random unless they are corrupted with noise. The spatial information or the appearance of various objects in many real images are inherently imprecise and non-random. A random process in an image is considered when the histogram of the image is used and treated as a probability density function that expresses the probable occurrence of a certain gray level in the image.

Analysis of typical textural images

Fig. 1 shows the gray-scale images of (a) “Lena” (512×512), (b) partial cancer cell (603×1819), (c) partial normal cell (678×1447), and (d) human abdominal organs (246×366). The cancer cell is of cell lines derived from a human head and neck squamous cell carcinoma (SCC-61). The normal cell is of mouse embryonic fibroblast (MEF) cells. Both cell images were produced by the combination of the focused-ion-beam and scanning-electron-microscope techniques. The organelles of the cancer and normal

Conclusion

A new concept for calculating the K–S entropy in the framework of the theory of fuzzy sets has been presented and applied to extract a useful feature for texture image analysis and classification, while the modeling of the K–S entropy for images is difficult to construct. The fuzzy K–S entropy of an image is a number that characterizes the nonlinear behavior of an ensemble of fuzzy membership grades of a partition of an image space. The extended framework of the K–S entropy can be useful for

Conflict of interest

The author declares that there are no conflicts of interest.

Acknowledgments

The author thanks the Handling Editor, Nicole Vincent, and the two anonymous reviewers for their constructive comments and suggestions, which helped improve the paper. The microscope (cell) images were provided by Kazuhisha Ichikawa of the Institute of Medical Science of the University of Tokyo. The CT (abdomen) image was provided by Taichiro Tsunoyama of the Teikyo University School of Medicine. Satoshi Haga of the University of Aizu assisted the author in partial coding and testing the

Tuan D. Pham received his Ph.D. degree in Civil Engineering in 1995 from the University of New South Wales, Sydney, Australia. He is a Professor of Biomedical Engineering at Linkoping University, Sweden. Prior to this current position, he held positions as a Professor and a Leader of the Aizu Research Cluster for Medical Engineering and Informatics at The University of Aizu, Japan; and Group Leader of Bioinformatics Research at The University of New South Wales, Canberra, Australia.

His current

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    Tuan D. Pham received his Ph.D. degree in Civil Engineering in 1995 from the University of New South Wales, Sydney, Australia. He is a Professor of Biomedical Engineering at Linkoping University, Sweden. Prior to this current position, he held positions as a Professor and a Leader of the Aizu Research Cluster for Medical Engineering and Informatics at The University of Aizu, Japan; and Group Leader of Bioinformatics Research at The University of New South Wales, Canberra, Australia.

    His current research interests include image processing, pattern recognition, fractals and chaos applied to biology and medicine. His research has been funded by the Australian Research Council, JSPS (Japan), academic institutions, and industry. He has served as an Area Editor, Associate Editor, and Editorial Board Member of several journals and book series including Pattern Recognition (Elsevier), Current Bioinformatics (Bentham), Recent Patents on Computer Science (Bentham), Proteomics Insights (open access journal, Libertas Academica Press), Book Series on Bioinformatics and Computational BioImaging (Artech House), International Journal of Computer Aided Engineering and Technology (Inderscience Publishers). Pham has served as chair and technical committee member of more than 30 international conferences in the fields of image processing, pattern recognition, and computational life sciences.

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