CN110570404A - Sobel operator-based cloth defect detection method - Google Patents

Sobel operator-based cloth defect detection method Download PDF

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CN110570404A
CN110570404A CN201910789108.6A CN201910789108A CN110570404A CN 110570404 A CN110570404 A CN 110570404A CN 201910789108 A CN201910789108 A CN 201910789108A CN 110570404 A CN110570404 A CN 110570404A
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block
image block
sobel operator
pixel values
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江结林
王博恒
马利
金子龙
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Nanjing University of Information Science and Technology
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/0002Inspection of images, e.g. flaw detection
    • G06T7/0012Biomedical image inspection
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/10Segmentation; Edge detection
    • G06T7/11Region-based segmentation
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/10Segmentation; Edge detection
    • G06T7/13Edge detection
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/10Segmentation; Edge detection
    • G06T7/136Segmentation; Edge detection involving thresholding
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/20Special algorithmic details
    • G06T2207/20021Dividing image into blocks, subimages or windows
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/30Subject of image; Context of image processing
    • G06T2207/30108Industrial image inspection
    • G06T2207/30124Fabrics; Textile; Paper

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Abstract

the invention discloses a defect detection method based on a Sobel operator, and belongs to the field of image detection. Firstly, Sobel operator filtering is carried out on an image to obtain a preliminary binaryzation defect image, then, the preliminary defect detection image is partitioned, the number of nonzero pixel values in each image block is counted, the image blocks are partitioned into image blocks containing defects and image blocks not containing defects by combining a threshold value, and finally, the image blocks are synthesized into the defect image. To further suppress noise, the composite image block is subjected to a loop process of further blocking the composite image block by a threshold value. The invention establishes a new Sobel-IP defect detection method by combining a Sobel operator with image blocking. The edge detection effect of the Sobel operator is fully utilized, after an initial detection result is obtained, secondary blocking threshold processing is carried out on the image, defects in the cloth can be accurately detected, noise can be effectively suppressed, the cloth defect detection efficiency is improved, and the false detection rate is reduced.

Description

Sobel operator-based cloth defect detection method
Technical Field
The invention belongs to the technical field of image detection, and particularly relates to a cloth defect detection method based on a Sobel operator.
background
Cloth defect detection is a key step in ensuring the quality of cloth, and therefore has been a popular topic in the textile industry. The traditional detection of cloth mainly relies on people's vision to accomplish, and this kind of detection mode is not only inefficiency, and it is very high to detect the error rate moreover. There are studies showing that: even professional inspectors can only achieve the cloth inspection rate of about 70 percent [1 ]. In recent years, computer vision-based detection methods are adopted to make up for the defects of the traditional cloth defect detection, and the core of the methods is to design a quick and effective algorithm.
The existing defect detection methods are mainly divided into three categories: statistical-based methods, spectral methods, and model-based methods.
a typical gray level co-occurrence matrix method [2] is compared based on a statistical method, a spectrum method uses the spectrum characteristics of an image for defect detection, and the spectrum method mainly comprises Fourier transform [3] and wavelet transform [4 ]. The model-based method mainly starts from the structure of data, and typically comprises an autoregressive model [5] and a Markov random model [6 ].
The defects existing in the defect detection at present mainly comprise: (1) due to various reasons such as picture acquisition and the like, noise introduction is inevitable, so that the false detection rate of the common detection method is too high; (2) the partial defect detection method has the defects that the real-time detection is difficult to realize due to the complexity of the algorithm while the higher detection rate is obtained.
[1]H.Sari-Sarraf,JS.Goddard,Vision systems for on-loom fabric inspection.IEEE Trans.Ind.Appl,35(6),1252-1259(1999).
[2]A.Latif-Amet,A.Ertuzun,A.Ercil,An efficient method for texture defect detection:sub-band domain co-occurrence matrices,Image and VisionComputing 18,543–55(2000).
[3]CH.Chan,G.Pang,Fabric defect detection by Fourier analysis,IEEE Trans.Ind.Appl.36(5),1743-1750(2000).
[4]Y.Han,P.Shi,An adaptive level-selecting wavelet transform for texture defect detection,Image Vision Comput,25(8),1239-1248(2007).
[5]J.Zhou,D.Semenovich,A.Sowmya,J.Wang,Dictionary learning framework for fabric defect detection,The Journal of the Textile Institute,105(3),223-234(2014).
[6]S.Ozdemir,A.Ercil,Markov random fields and Karhunen-Loeve transform for defect inspection of textile products.IEEE Conference onEmerging Technologies&Factory Automation,1996,pp.697-703.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a cloth defect detection method based on Sobel operator, which aims at the problems that the false detection rate of the current cloth defect detection method is too high, and the real-time detection is difficult to realize when the partial defect detection method obtains higher detection rate. The method is based on Sobel operator combined with image block statistics, can effectively detect defects and inhibit noise, and can be applied to a real-time image processing system.
the technical scheme is as follows: in order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: a cloth defect detection method based on a Sobel operator comprises the following steps:
Step 1: carrying out Sobel operator filtering on the collected cloth defect image to obtain an initial estimation image;
step 2: partitioning the estimated image, and counting the number of non-zero pixel values in each image block to obtain a statistical result of the pixel values in each image block;
And step 3: setting a threshold value, and performing binarization processing on a statistical result of pixel values in an image block to obtain an image block after binarization processing;
And 4, step 4: synthesizing the image blocks after binarization processing to obtain a secondary estimation image;
and 5: repeating the steps 2 to 4 on the secondary estimation image obtained in the step 4 to obtain a final detection imageImplementing Sobel operator andAnd (5) carrying out image blocking statistical detection.
Further, the step 1 performs Sobel operator filtering on the acquired image to obtain an initial estimation image; the method comprises the following steps:
1-1, detecting the edges of the acquired cloth defect images y by using a Sobel operator, wherein the Sobel operator comprises two convolution kernels, namely a transverse convolution kernel and a longitudinal convolution kernel, and performing convolution operation on the transverse convolution kernel and the longitudinal convolution kernel and the defect images y respectively to obtain the cloth defect images y
Wherein is the convolution operator, Gxand GyRepresenting the image gradient values of the lateral and longitudinal edge detection, respectively;
1-2, after all pixels of the image are operated by a convolution operator, calculating the gradient size of the corresponding pixel according to the transverse and longitudinal gradient values of each pixel of the image, thereby obtaining a gradient image; the gradient magnitude calculation is as follows:
wherein G represents the gradient of the pixel point;
And 1-3, carrying out binarization operation on the gradient image obtained in the step 1-2 to obtain a binarized image, and recording the binarized image as x, wherein the binarized image is an initial estimation image.
Further, the step 2 is to block the estimated image, and count the number of non-zero pixel values in each image block to obtain a statistical result of the pixel values in each image block; the method comprises the following steps:
partitioning the image x according to a matrix block mining operator to obtain an image block xiexpressed as follows:
xi=Rix i=1,2,...,n
wherein R isifor the matrix block mining operator, n represents the number of image blocks, the scale of the blocks is m × m, there are 2 images between blocksThe prime values overlap; preferably, the block size is 7 × 7, which is the best detection result;
and after the image x is partitioned, counting the number of non-zero pixel values in each image block to obtain a statistical result of each image block.
Further, setting a threshold value in the step 3, and performing binarization processing on a statistical result of pixel values in the image block to obtain a binarized image block; the method comprises the following specific steps:
judging whether the number of the non-zero pixel values in each image block obtained in the step (2) meets a threshold condition or not;
if the number of the non-zero pixel values in the image block is larger than a set threshold, the image block contains defects, and the pixel values in the image block are kept unchanged; otherwise, the image block only contains noise points, the pixel value of the whole image block is set to be 0, and a binary image block is obtained
further, the image blocks after the binarization processing are synthesized in the step 4 to obtain a secondary estimation image; the method comprises the following steps: after all the binarized image blocks are obtained, the imageObtained by solving the following minimization problem:
The above formula is solved into
Will estimate the image blockPlacing the image at the corresponding position of the original image y, and averaging the pixel values at the overlapped pixel part to obtain a detection image
Further, the image obtained in step 4 is utilizedalthough part of the noise is suppressed, the noise is still present at this time. Due to the block-to-block overlap during defect detection, the noise becomes more and more sparse. To further reduce the false detection rate, the detection image is processedpartitioning is carried out again, the number of non-zero pixel values in each block is counted, and a final detection image is obtainedthrough twice circulation, the noise can be effectively reduced, and simultaneously the defects can be completely detected.
has the advantages that: compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:
the invention mainly solves the problem of cloth defect detection, establishes a new Sobel-IP defect detection method by combining an Image Patch (IP) statistical strategy through a Sobel operator, and finally realizes the aim of cloth intelligent detection. Compared with the existing defect detection algorithm, the Sobel-IP defect detection algorithm utilizes a Sobel operator to detect defect images, then blocks the images and carries out threshold processing, so that the real-time performance of the algorithm can be maintained in the detection, and meanwhile, the detection efficiency can be effectively improved. Due to the adoption of the secondary circulation algorithm, the noise can be effectively inhibited, and the purpose of reducing the false detection rate is achieved.
Drawings
FIG. 1 is a flow chart of image defect detection in accordance with the present invention;
FIG. 2 is an illustration of a sample of the present invention.
Detailed Description
the technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
the invention discloses a cloth defect detection method based on a Sobel operator, which has a detection flow shown in figure 1 and comprises the following steps:
step 1: performing Sobel operator filtering on the cloth defect image acquired by the industrial camera to obtain an initial estimation image; the method comprises the following specific steps:
1-1, detecting the edges of the acquired cloth defect image y by using a Sobel operator, wherein the Sobel operator comprises two convolution kernels, namely a transverse convolution kernel and a longitudinal convolution kernel; respectively carrying out convolution operation on the transverse convolution kernel and the longitudinal convolution kernel and the defect image y to obtain
Wherein is the convolution operator, GxAnd GyRepresenting the image gradient values of the lateral and longitudinal edge detection, respectively;
1-2, after all pixels of the image are operated by a convolution operator, calculating the gradient size of the corresponding pixel according to the transverse and longitudinal gradient values of each pixel of the image, thereby obtaining a gradient image; the gradient magnitude calculation is as follows:
And 1-3, carrying out binarization operation on the gradient image obtained in the step 1-2 to obtain a binarized image, and recording the binarized image as x, wherein the binarized image is an initial estimation image.
Step 2: partitioning the estimated image, and counting the number of non-zero pixel values in each image block to obtain a statistical result of the pixel values in each image block; the method comprises the following specific steps:
partitioning the image x according to a matrix block mining operator to obtain an image block xiExpressed as follows:
xi=Rix i=1,2,...,n
Wherein R isiFor the matrix block mining operator, n denotes the number of image blocks, the scale of the blocks is 7 x 7,There is 2 pixel value overlap between blocks;
and after the image x is partitioned, counting the number of non-zero pixel values in each image block to obtain a statistical result of each image block.
And step 3: setting a threshold value, and performing binarization processing on a statistical result of pixel values in an image block to obtain an image block after binarization processing; the method comprises the following specific steps:
Judging whether the number of the non-zero pixel values in each image block obtained in the step (2) meets a threshold condition or not;
If the number of the non-zero pixel values in the image block is larger than a set threshold, the image block contains defects, and the pixel values in the image block are kept unchanged; otherwise, the image block only contains noise points, the pixel value of the whole image block is set to be 0, and a binary image block is obtained
and 4, step 4: synthesizing the image blocks after binarization processing to obtain a secondary estimation image; the method comprises the following steps:
After all the binarized image blocks are obtained, the imageObtained by solving the following minimization problem:
the above formula is solved into
will estimate the image blockPlacing the image at the corresponding position of the original image y, and averaging the pixel values at the overlapped pixel part to obtain a detection image
And 5: repeating the steps 2 to 4 on the secondary estimation image obtained in the step 4 to obtain a final detection imageand realizing Sobel operator and image block statistical detection.
Using the image obtained in step 4Although part of the noise is suppressed, the noise is still present at this time. Due to the block-to-block overlap during defect detection, the noise becomes more and more sparse. To further reduce the false detection rate, the detection image is processedPartitioning is carried out again, the number of non-zero pixel values in each block is counted, and a final detection image is obtainedThrough the two-step circulation, the noise can be effectively reduced, and simultaneously the defects can be completely detected.
In the embodiment, the detection method of the sobel operator and the image block statistics is used for the defect picture test, and the result shows that the method not only effectively improves the defect detection efficiency, but also reduces the false detection rate and obtains better detection performance.
Some specific detection examples are given below. As shown in fig. 2, fig. 2(a), 2(b) and 2(c) are defect images, and fig. 2(d), 2(e) and 2(f) are cloth defect detection effect graphs based on Sobel operator combined image blocking statistics according to this embodiment.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiment according to the technical spirit of the present invention are included in the protection scope of the present invention.

Claims (5)

1. a cloth defect detection method based on a Sobel operator is characterized by comprising the following steps: the method comprises the following steps:
step 1: carrying out Sobel operator filtering on the collected cloth defect image to obtain an initial estimation image;
Step 2: partitioning the estimated image, and counting the number of non-zero pixel values in each image block to obtain a statistical result of the pixel values in each image block;
And step 3: setting a threshold value, and performing binarization processing on a statistical result of pixel values in an image block to obtain an image block after binarization processing;
and 4, step 4: synthesizing the image blocks after binarization processing to obtain a secondary estimation image;
And 5: and (4) repeating the steps 2 to 4 on the secondary estimation image obtained in the step 4 to obtain a final detection image, and realizing the block statistical detection of the Sobel operator and the image.
2. the Sobel operator-based cloth defect detection method according to claim 1, further comprising: step 1, Sobel operator filtering is carried out on the cloth defect image to obtain an initial estimation image; the method comprises the following steps:
1-1, detecting the edges of the acquired cloth defect images y by using a Sobel operator, wherein the Sobel operator comprises two convolution kernels, namely a transverse convolution kernel and a longitudinal convolution kernel, and performing convolution operation on the transverse convolution kernel and the longitudinal convolution kernel and the defect images y respectively to obtain the cloth defect images y
wherein is the convolution operator, GxAnd GyRepresenting the image gradient values of the lateral and longitudinal edge detection, respectively;
1-2, after all pixels of the image are operated by a convolution operator, calculating the gradient size of the corresponding pixel according to the transverse and longitudinal gradient values of each pixel of the image, thereby obtaining a gradient image; the gradient magnitude calculation is as follows:
wherein G represents the gradient of the pixel point;
And 1-3, carrying out binarization operation on the gradient image obtained in the step 1-2 to obtain a binarized image, and recording the binarized image as x, wherein the binarized image is an initial estimation image.
3. the Sobel operator-based cloth defect detection method according to claim 2, wherein: the step 2 is to divide the estimated image into blocks and count the number of non-zero pixel values in each image block to obtain the statistical result of the pixel values in each image block; the method comprises the following steps:
Partitioning the image x according to a matrix block mining operator to obtain an image block xiExpressed as follows:
xi=Rix i=1,2,...,n
Wherein R isimining operators for matrix blocks, wherein n represents the number of image blocks, the scale of each block is m multiplied by m, and 2 pixel values are overlapped among the blocks;
And after the image x is partitioned, counting the number of non-zero pixel values in each image block to obtain a statistical result of each image block.
4. The Sobel operator-based cloth defect detection method according to claim 3, wherein: setting a threshold value, and performing binarization processing on a statistical result of pixel values in the image block to obtain an image block after binarization processing; the method comprises the following specific steps:
judging whether the number of the non-zero pixel values in each image block obtained in the step (2) meets a threshold condition or not;
If the number of the non-zero pixel values in the image block is larger than a set threshold, the image block contains defects, and the pixel values in the image block are kept unchanged; otherwise, the image block only contains noise points, the pixel value of the whole image block is set to be 0, and binarization is obtainedImage block of
5. the Sobel operator-based cloth defect detection method according to claim 4, wherein: step 4, synthesizing the image blocks after binarization processing to obtain a secondary estimation image; the method comprises the following steps:
After all the binarized image blocks are obtained, the imageobtained by solving the following minimization problem:
The above formula is solved into
will estimate the image blockPlacing the image at the corresponding position of the original image y, and averaging the pixel values at the overlapped pixel part to obtain a detection image
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CN111768376A (en) * 2020-06-24 2020-10-13 山东科技大学 Eddy current thermal imaging edge detection method and system, storage medium and application
CN112365448A (en) * 2020-10-20 2021-02-12 天津大学 Fabric defect detection method in warp knitting process
CN112435232A (en) * 2020-11-23 2021-03-02 南京信息工程大学 Defect detection method based on haar wavelet combined image variance
CN114882034A (en) * 2022-07-11 2022-08-09 南通世森布业有限公司 Fabric dyeing quality evaluation method based on image processing

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111768376A (en) * 2020-06-24 2020-10-13 山东科技大学 Eddy current thermal imaging edge detection method and system, storage medium and application
CN112365448A (en) * 2020-10-20 2021-02-12 天津大学 Fabric defect detection method in warp knitting process
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CN112435232A (en) * 2020-11-23 2021-03-02 南京信息工程大学 Defect detection method based on haar wavelet combined image variance
CN114882034A (en) * 2022-07-11 2022-08-09 南通世森布业有限公司 Fabric dyeing quality evaluation method based on image processing

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Application publication date: 20191213