Abstract
Colored spun fabrics are difficult to accurately characterize with a local binary pattern due to texture anisotropy caused by the uneven distribution of dyed fibers. In this paper, we present a texture representation model based on spatial and frequency characteristics. The proposed model takes advantage of the local binary pattern and local phase quantization to extract the texture of woven fabric. Then, the two features are connected in series, and the features of dimension reduction by principal component analysis are used to represent the texture of the fabric image. Finally, the hierarchical hybrid classifier is applied to classify the fabric structure. The experimental results show that the local phase quantization feature is robust to the fuzzy transformation and the texture representation model has a stronger ability of texture description than the single local binary pattern feature, with the average classification accuracy of 97.59% on 336 samples. In addition, compared with the deep learning algorithm, the texture representation algorithm can ensure a high classification accuracy.
Keywords
Woven fabric is composed of warp and weft yarns interweaved vertically according to certain rules, and its texture has certain periodicity, directionality and structure characteristics. 1 Effective extraction or representation can not only promote fabric quality index evaluation, but also lay a foundation for fabric quality detection. At present, the application of fabric texture representation mainly involves two aspects:2–4 (a) objective measurement of the geometric or statistical characteristics of the fabric surface texture, such as the grade estimation of the fabric wrinkles, the detection of the fabric density, the automatic identification of the fabric weave, etc.; (b) abnormal analysis of fabric surface texture features, such as automatic detection of fabric defects.
Common texture representation methods can be divided into statistical methods, structure methods, model methods, filtering methods and deep learning methods.5,6 Combining with different structural features and application requirements of textiles, many research institutions and teams at home and abroad have conducted extensive research on texture representation algorithms of fabric images.
Due to the advantages of the linear binary pattern (LBP) in texture representation, a large number of LBP optimization and improvement algorithms have emerged in recent years. These methods can be roughly classified into three categories:7–9 (a) changing coding or mode selection; (b) changing the domain topology or sampling structure; (c) combining the LBP with other complementary features. Pawening et al. 10 proposed a textile image classification algorithm based on the linear binary pattern and gray-level co-occurrence matrix (GLCM). Compared with the single feature, the fusion feature information had the best accuracy. Tajeripour et al. 11 made use of modified LBPs to conduct defect detection in patterned fabrics. This method was effective for testing star patterned fabrics, dot patterned fabrics and box patterned fabrics with a detection rate of over 95%. Liu et al. 12 applied the main local binary pattern (MLBP) to reconstruct the fabric texture, and achieved defect detection. Li et al. 13 converted the fabric image from RGB color space to LAB color space and extracted the LBP operator of the energy-based feature images to defect defects with a detection success rate of more than 94.09%. Zhang et al. 14 put forward local statistics and global analysis to achieve the effective representation of fabric texture.
Unlike a monochromatic object, colored spun fabrics use dyed fibers as the basic carrier of color, as shown in Figure 1. In the process of yarn forming or weaving, the dyed fiber appears as a spiral related to the twist on the surface of yarn or fabric and the fibers stack and gather with each other. Hence, this heterogeneity and anisotropy destroy the original periodicity, directivity and structural characteristics of the colored spun fabric, resulting in fabric texture image blur and obvious noise.
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However, the LBP algorithm can only extract the spatial features of the image, that is, process the gray-level changes between image pixels, and cannot reflect the gradient changes between pixels, that is, the frequency information, which has certain limitations.
Colored spun fabrics.
In order to solve this problem, a texture representation model of colored spun woven fabric is proposed in this paper, which combines spatial and frequency features. Firstly, the feature values are extracted by the LBP and local phase quantization (LPQ) from woven fabric images, respectively. Then, the serial feature of the LBP and LPQ is optimized by applying principal component analysis (PCA) to reduce the dimension. Finally, the optimized texture features are used as the input of a hierarchical hybrid classifier to classify colored spun woven fabrics.
The structure of this paper is organized as follows. In the second section, we introduce the research method in detail. In the third section, we give experiments and results, including experiment preparation, parameter optimization, experimental results and comparison experiments. Conclusions follow in the last section.
Research method
LBP algorithm
The LBP is a classical algorithm used to describe the local texture features of images. Its basic principle is to compare the gray values of the central pixel and the domain pixel. If the gray value of a domain pixel is greater than or equal to the gray value of the central pixel, it is set to 1; otherwise, it is set to 0. The rules are shown in the following equations
In Equation (1), gc is the gray value of the center pixel, gi is the gray value of the pixels in its domain, P represents the number of surrounding pixels and R represents the domain radius of the center. In order to further improve the applicable range of the LBP operator, it can be extended to the LBP algorithm with a variable region, and the circle field can be employed to replace the square field. 16
LPQ algorithm
The LPQ algorithm uses short-time Fourier transform (STFT) to calculate the local phase information of pixels on the image.
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The image
Fusion of LBP and LPQ features
No matter whether in the spatial domain or the frequency domain, some information is always lost in the texture analysis. The combination of the two can complement each other and enhance the ability of texture description. Therefore, the texture image and histogram features of the colored spun woven fabric extracted by the LBP and LPQ are shown in Figure 2.
Colored spun woven fabric texture features in spatial and frequency domains: (a) original picture of colored spun woven fabric; (b) local binary pattern (LBP) pseudo grayscale of colored spun woven fabric; (c) local phase quantization (LPQ) pseudo grayscale of colored spun woven fabric; (d) LBP histogram features; (e) LPQ histogram features.
It can be seen from Figure 2 that there are significant differences between the LBP and LPQ texture features of the plain weave, that is, the ability to depict texture is different and complementary. The fusion of the two features can improve the ability of texture feature descriptors to represent complex modes. The details are as follows
PCA is a multivariate statistical method, which transforms a set of related variables into a set of orthogonal and unrelated variables through orthogonal transformation. The transformed variables are called principal components. Its goal is to extract the most important information from the data set and compress the size of the data set by reducing the dimensions without losing too much information. Here,
Experiments and results
Experimental preparation
Parameters of the first batch of experimental samples for colored spun woven fabric
Weaving process parameters of the first batch of colored spun woven fabric samples
Parameters of the second batch of colored spun woven fabric
After all samples are balanced at a relative humidity of 65%, we make use of the DigiEye Digital Imaging System to acquire images, and perform white balance and color correction on the DigiEye system camera through whiteboard and standard color card before acquisition. Then, eight standard images of different areas are acquired for each fabric sample and are segmented to obtain 896 sample images of 256 × 256 pixels. Finally, 560 images are chosen as the training samples and the rest as testing samples. Some samples are shown in Figure 3.
Some experimental samples of colored spun woven fabric: (a) SS41A; (b) SS51D; (c) SS41F; (d) 17001; (e) 17018.
The experimental operation platform is the ultra micro 7048GR-TR deep learning system, Windows 10 operating system, Intel(R) Xeon(R) E5-2678V3*2 CPU, 128 G RAM and NVIDIA Tesla M40*2 operation card. The algorithm development environment is MATLAB 2015b and Python3.7, and TensorFlow-gpu1.14.0, CUDA Toolkit10.0 and cuDNN7.4 are installed.
Parameter optimization
Fabric weave classification results under different parameters of the local binary pattern operator
Classification results of image block size and fabric structure
Window size of the local phase quantization operator and fabric structure classification results
The results show that LPQ has the best ability of texture representation and the highest classification accuracy at
Experimental results and analysis
Classification results with twist factor of 330
Classification results with twist factor of 370
Classification results of the first batch of samples with the same quality ratio of dyed fibers
The results show that the texture representation model established in this paper can effectively express the texture change caused by the blending differences of dyed fibers and the changes in the twist coefficient of colored spun yarns. The classification accuracy of plain weave is stable at 100%, and those of twill and satin weave are kept above 90%, which verifies the effectiveness and robustness of the texture representation model. However, it is worth noting that some abnormal fluctuations occur in the experimental results. For example, the classification accuracy of SS63D and SS53F is relatively low. By comparing and analyzing the sample images, it is found that similar fluctuations are mainly due to the abnormal aggregation and stacking of dyed fibers in local areas of some samples, as shown in Figure 4.
Abnormal aggregation of dyed fibers in colored spun woven fabrics.
Experimental results of the second batch of colored spun woven fabrics
The results show that the classification accuracy of plain weave fabrics is stable at 100%. Therefore, the change of the fibrous materials and the color of the dyed fibers have no effect on the classification of the fabric, which is robust.
Comparison results
Comparative experimental results
The experimental results show that, compared with the classical deep learning algorithm of the DBN and CNN, the texture representation model established in this paper can effectively fuse the spatial and frequency domain texture features of the woven fabric image, and has the ability of effective and stable texture description. In the process of fabric texture classification, the overall classification accuracy is 97.59%, which is better than that of the comparison method.
Conclusions
In this paper, a texture representation model of colored spun woven fabric is proposed, which combines spatial and frequency features. This model uses the fusion features of the LBP and LPQ to describe fabric images, and realizes the classification of colored spun woven fabrics by means of a hierarchical hybrid classifier. The experimental results show that the LPQ feature is robust to the fuzzy transformation and the texture representation model has stronger ability of texture description and anti-noise than the single local binary mode feature. At the same time, compared with the deep learning algorithm, the texture representation algorithm can ensure a high classification accuracy.
The research in this paper can provide technical support for the reconstruction, classification and defect detection of colored spun woven fabric images. Moreover, whether fibrous materials and the color of dyed fiber have an impact on the texture change of colored spun fabrics will be the authors’ next research direction.
Footnotes
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors disclosed receipt of the following financial support for the research, authorship and/or publication of this article: This work was supported by the Natural Science Foundation of Hubei Province (No. 2014CFB754), the Young Talents Project of Science and Technology Research of the Hubei Provincial Department of Education (No. Q20141607) and the Science and Technology Guiding Project of the China National Textile and Apparel Council (No. 2018035 and No. 2014072).
