Texture Classification Using Hilbert Curve-Based Information Quantifiers

Основні поняття

A novel method for texture classification that transforms 2D images into 1D time series using the Hilbert curve and then computes information theory quantifiers to effectively discriminate between different texture classes.

Анотація

The proposed method consists of the following steps:

The 2D image is transformed into a 1D time series using the Hilbert curve, which effectively captures the spatial relationships between pixels while avoiding directional biases.

The Bandt and Pompe symbolization method is used to construct the probability density function from the 1D time series.

Three information theory quantifiers are computed: permutation entropy, permutation statistical complexity, and Fisher information measure.

The complexity-entropy causality plane (CECP) and the Fisher-entropy causality plane (FECP) are used to classify the textures based on the computed quantifiers.

The method is evaluated on several datasets:

Self-similar multifractal surfaces: The method can effectively discriminate between regular, ordered, and random textures, and is invariant to rotations and mirror-symmetry transformations.

Brownian surfaces: The method can accurately classify textures based on their Hurst exponents, which characterize the roughness of the surfaces. The results are also invariant to rigid transformations.

Normalized Brodatz database: The method can effectively discriminate between different real-world textures, and the addition of the Fisher information measure enhances the discrimination capabilities compared to previous approaches.

Colored Brodatz database: The method is robust to color variations and can be applied to both grayscale and color images.
The key advantages of the proposed method are its ability to effectively capture the spatial characteristics of textures, its invariance to rigid transformations, and its potential for extension to higher-dimensional patterns.

Статистика

The paper presents several quantitative results, including:

The Hurst exponent values used to generate the Brownian surfaces (H ∈ {0.1, 0.2, ..., 0.9}).
The embedding dimension (D = 5, 6, 7, 8) and delay (τ = 1) parameters used in the calculations.

Цитати

"The proposed method exhibits some important properties: (i) it allows to discriminate figures according to varying degrees of correlations (as measured by the Hurst exponent), (ii) it is invariant to rotation and symmetry transformations, (iii) it can be used either in black and white or color images."
"The key point is that there is no a uniquely predetermined order, when P is defined on two –or higher– dimension patterns, to convert a matrix into a symbol."
"The Hilbert curve was chosen to effectively transform spatial correlations into temporal ones."

Ключові висновки, отримані з

Texture Discrimination via Hilbert Curve Path Based Information Quantifiers

by Aure... о arxiv.org 09-25-2024

https://arxiv.org/pdf/2409.15327.pdf

Глибші Запити

How could the proposed method be extended to handle higher-dimensional patterns, such as 3D or 4D images?

The proposed method can be extended to handle higher-dimensional patterns, such as 3D or 4D images, by leveraging the properties of the n-dimensional Hilbert curve. The Hilbert curve is a space-filling curve that can be generalized to n dimensions, allowing for the traversal of multi-dimensional data while preserving locality. To implement this extension, the following steps could be taken:

Generalization of the Hilbert Curve: Develop an algorithm to generate the n-dimensional Hilbert curve, which would map the multi-dimensional image data into a one-dimensional sequence while maintaining the spatial relationships between pixels or voxels.

Symbolization Method Adaptation: Modify the Bandt & Pompe symbolization method to accommodate the n-dimensional data. This would involve defining patterns based on the ordinal relations of neighboring values in higher dimensions, ensuring that the resulting symbolic sequences capture the intrinsic characteristics of the data.

Information Theory Quantifiers: Extend the computation of information theory quantifiers, such as permutation entropy, statistical complexity, and Fisher information measure, to n-dimensional contexts. This may require the development of new formulations or adaptations of existing quantifiers to account for the increased complexity and interactions present in higher-dimensional data.

Validation and Testing: Conduct empirical tests using synthetic and real-world 3D or 4D datasets to validate the effectiveness of the extended method. This would involve analyzing the robustness of the method against transformations and its ability to classify textures accurately.

By following these steps, the proposed method could effectively analyze and classify textures in higher-dimensional patterns, broadening its applicability in fields such as medical imaging, 3D modeling, and volumetric data analysis.

What other types of information theory quantifiers could be explored to further enhance the texture classification capabilities of the method?

To enhance the texture classification capabilities of the proposed method, several additional information theory quantifiers could be explored:

Kullback-Leibler Divergence: This quantifier measures the difference between two probability distributions. By incorporating Kullback-Leibler divergence, the method could assess how well the texture distributions of different images match, providing insights into texture similarity and aiding in classification tasks.

Renyi Entropy: An extension of Shannon entropy, Renyi entropy allows for the tuning of the sensitivity to different probability distributions through a parameter α. This flexibility can help capture various aspects of texture complexity and provide a more nuanced understanding of texture characteristics.

Lempel-Ziv Complexity: This quantifier measures the complexity of a sequence based on the number of distinct substrings. By integrating Lempel-Ziv complexity, the method could evaluate the richness of texture patterns, distinguishing between simple and complex textures effectively.

Transfer Entropy: This quantifier measures the amount of directed (or causal) information transfer between two time series. In the context of texture classification, transfer entropy could be used to analyze the interactions between different texture features, enhancing the understanding of texture dynamics.

Multi-scale Entropy: This approach assesses the complexity of a signal at multiple scales. By applying multi-scale entropy to texture analysis, the method could capture variations in texture patterns across different resolutions, improving classification accuracy.

By incorporating these additional information theory quantifiers, the proposed method could achieve a more comprehensive and robust texture classification, enabling it to handle a wider variety of textures and improve its performance in practical applications.

How could the method be adapted to handle non-square or irregularly shaped images?

Adapting the proposed method to handle non-square or irregularly shaped images involves several key modifications:

Flexible Hilbert Curve Mapping: Instead of relying solely on a traditional square-based Hilbert curve, develop a flexible mapping algorithm that can adapt the Hilbert curve traversal to fit the contours of irregularly shaped images. This could involve defining a custom path that respects the boundaries of the image while still maintaining the locality-preserving properties of the Hilbert curve.

Boundary Handling: Implement techniques to handle the boundaries of non-square images effectively. This may include padding the image to a square shape or using a modified version of the Hilbert curve that accounts for the irregular edges, ensuring that all pixels are visited without introducing significant bias.

Adaptive Symbolization: Modify the Bandt & Pompe symbolization method to accommodate the unique pixel arrangements in non-square images. This could involve defining patterns based on the local neighborhood of pixels, ensuring that the symbolization process captures the texture characteristics accurately.

Dynamic Resizing: Introduce a dynamic resizing mechanism that adjusts the embedding dimensions and delay parameters based on the image's aspect ratio and shape. This would ensure that the information theory quantifiers are computed effectively, regardless of the image's dimensions.

Validation with Diverse Datasets: Test the adapted method on a variety of non-square and irregularly shaped images to validate its effectiveness. This would involve analyzing the robustness of the method against transformations and its ability to classify textures accurately in diverse scenarios.

By implementing these adaptations, the proposed method could effectively analyze and classify textures in non-square or irregularly shaped images, expanding its applicability in various fields, including remote sensing, medical imaging, and artistic analysis.