Edge Detection in Noisy Images by Neuro
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8/2/2019 Edge Detection in Noisy Images by Neuro
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Edge detection in noisy images by neuro-fuzzy processing
M. Emin Yksel ,a, [Author vitae]
aDigital Signal and Image Processing Laboratory, Department of Electrical and Electronics
Engineering, Erciyes University, Kayseri, 38039, Turkey
Received 21 December 2005.
Available online 29 March 2006.
Abstract
A novel neuro-fuzzy (NF) operator for edge detection in digital images corrupted by
impulse noise is presented. The proposed operator is constructed by combining a desirednumber of NF subdetectors with a postprocessor. Each NF subdetector in the structure
evaluates a different pixel neighborhood relation. Hence, the number of NF subdetectors inthe structure may be varied to obtain the desired edge detection performance. Internalparameters of the NF subdetectors are adaptively optimized by training by using simple
artificial training images. The performance of the proposed edge detector is evaluated on
different test images and compared with popular edge detectors from the literature.Simulation results indicate that the proposed NF operator outperforms competing edge
detectors and offers superior performance in edge detection in digital images corrupted by
impulse noise.
Keywords:Neuro-fuzzy systems; Image processing; Edge detection
Article Outline
1.
Introduction2.
Method
2.1.The proposed neuro-fuzzy operator2.2.The neuro-fuzzy subdetectors
2.3.The postprocessor
2.4.Training of the neuro-fuzzy subdetectors
2.5.Processing of the noisy input image
3.Results
4.Discussion and conclusion
References
Vitae
1. Introduction
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8/2/2019 Edge Detection in Noisy Images by Neuro
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Edges in a digital image provide important information about the objects contained within
the image since they constitute the boundaries between the objects in the image. Edge
detection is a frequently performed operation in many image processing applicationsbecause it is usually the first operation that is performed before other image processing
tasks such as image segmentation, boundary detection, object recognition and
classification, image registration, and so on. Consequently, the success of these subsequentimage processing tasks are strictly dependent on the performance of the edge detection
operation.
The image intensity shows sudden changes at edges. Therefore, edge detection usually
involves the calculation of the derivative of the image intensity function at a given pixellocation. If the magnitude of the derivative of the image intensity function is relatively high
at a given pixel location, then the pixel at that image location is classified as an edge pixel.
The most important factor decreasing the performance of edge detection is the noise.
Unfortunately, digital images are inevitably degraded by noise during image acquisition
and/or transmission due to a number of imperfections encountered in imaging processesand/or communication channels. Most edge detection operators are based on the
assumption that images contain large homogeneous regions separated by clear boundaries.However, this assumption loses its validity if the image is corrupted by noise. Therefore,
majority of the edge detection operators require a prefiltering of the noisy image by using
an appropriate noise filter before edge detection is performed. In this case, however, theperformance of the edge detection operation becomes strictly dependent on the
performance of the noise filter. Moreover, the complexity of the system and the processing
time are considerably increased.
A number of methods for edge detection implementing different approaches to the digital
calculation of the derivative of the image intensity function are available in the literature.The classical methods [1] and[2] such as the Sobel, Prewitt and Kirsch detectors calculate
the first directional derivative to determine the locations of the edges. These detectors aresimple to implement but they are usually inaccurate and highly sensitive to noise. The zero-
crossing edge detectors [1] and[2] use the second derivative along with the Laplacian
operator. These detectors have fixed detection characteristics in all directions but they are
very sensitive to noise too. The Gaussian edge detectors[2]reduce the undesirable negativeeffects of noise by smoothing the image before performing edge detection. Hence, they
exhibit much superior performance over other operators especially in noisy conditions. The
Canny detector, which is a Gaussian edge detector, is one of the most popular edgedetectors in the literature and it has been widely used in many applications [3], [4] and [5].
Although the Gaussian detectors exhibit relatively better performance, they are
computationally much more complex than classical derivative based edge detectors.Furthermore, their performances quickly decrease as the density of the corrupting noise
increases. Therefore, a novel edge detector that is capable of extracting edges from digital
images corrupted by noise is highly desirable.
In the last few years, there has been a growing research interest in the applications of softcomputing based techniques, such as neural networks and fuzzy logic systems, to various
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib1http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib1http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib3http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib4http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib5http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib1http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib2http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_r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8/2/2019 Edge Detection in Noisy Images by Neuro
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problems in image processing [6],[7], [8], [9],[10],[11],[12],[13],[14] and[15]. This is
due mainly to the fact that neuro-fuzzy (NF) systems are very suitable tools to deal with
uncertainty encountered in the process of extracting useful information from noisy imagessince NF systems combine the ability of neural networks to learn from examples and the
capability of fuzzy logic systems to model the uncertainty and imprecision. Hence, NF
systems may be employed as powerful tools for edge detection provided that appropriatenetwork topologies and training strategies are chosen.
In our recent work, we have shown that a NF system may be utilized to remove impulse
noise from digital images [16] and[17]; to construct highly efficient hybrid filters for
restoring noisy digital images while preserving edges, lines and other useful informationwithin the image [18]; to detect noise for guiding switching noise filters and reducing their
undesirable blurring effects [19] and [20]; and to improve noise suppression and detail
preservation performances of image filters [21]. In addition to these successfulapplications, we have also shown in a preliminary report [22] that NF systems may be
employed for efficient detection of edges in noisy digital images.
In this paper, we extend our preliminary research on edge detection and present a novel NF
method for edge detection in digital images corrupted by impulse noise. In the proposedmethod, the edges in the noisy image are directly determined by a NF network without
needing a prefiltering of the noisy input image. The NF network consists of a desired
number of subdetectors and a postprocessor. Each subdetector evaluates a different pixelneighborhood in the filtering window. The proposed NF edge detector is tested on popular
images having different image properties and also compared with popular edge detectors
from the literature. Experimental results show that the proposed NF edge detector exhibits
much better performance than the competing operators and may efficiently be used for thedetection of edges in digital images corrupted by impulse noise.
2. Method
2.1. The proposed neuro-fuzzy operator
Fig. 1a shows the general structure of the proposed NF edge detection operator. The
operator is constructed by combining a desired number of NF subdetectors with apostprocessor. All NF subdetectors in the structure operate on the same 3-by-3 pixel
filtering window, which is shown in Fig. 1b. Each NF subdetector evaluates a different
neighborhood relation between the center pixel of the filtering window and two of its
neighbors. Some of the many possible neighborhood topologies are shown in Fig. 1c. The
higher the number of NF subdetectors, the better the edge detection performance, but thehigher the computational cost.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib6http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib7http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib7http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib8http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib9http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib9http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib10http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib11http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib11http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib11http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib12http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib13http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib13http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1503824732&_rerunOrigin=google&_acct=C000063390&_version=1&_urlVersion=0&_userid=4555062&md5=7a172970008b5611b029f7b91e07367c&searchtype=a#bib13http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GWW-4JKHN7S-1&_user=4555062&_coverDate=02%2F01%2F2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=15038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Full-size image (42K)
Fig. 1. (a) The general structure of the proposed neuro-fuzzy edge detection operator. Thepixels applied to the inputs of each NF subdetector in the structure are chosen so as to
utilize the information from a different pixel neighborhood; (b) The filtering window of the
operator; (c) Some of the possible pixel neighborhood topologies.
2.2. The neuro-fuzzy subdetectors
Each NF subdetector is a first-order Sugeno type fuzzy inference system with 3-inputs and
1-output. The internal structures of the NF subdetectors are identical to each other. Eachinput has 3generalized belltype membership functions and the output has a linearmembership function. The inputoutput relationship of any of the NF subdetectors is asfollows:
LetX1,X2,X3denote the inputs of the NF subdetector and Ydenote its output. Eachpossible combination of inputs and their associated membership functions is represented by
a rule in the rule base of the NF subdetector. Since the NF subdetector has 3 inputs andeach input has 3 membership functions, the rule base contains a total of 27 (33) rules, which
are as follows:
1. if (X1 isM11) and (X2 isM21) and (X3 isM31), thenR1=F1(X1,X2,X3)
2. if (X1 isM11) and (X2 isM21) and (X3 isM32), thenR2=F2(X1,X2,X3)
3. if (X1 isM11) and (X2 isM21) and (X3 isM33), thenR3=F3(X1,X2,X3)
4. if (X1 isM11) and (X2 isM22) and (X3 isM31), thenR4=F4(X1,X2,X3)
5. if (X1 isM11) and (X2 isM22) and (X3 isM32), thenR5=F5(X1,X2,X3)
27. if (X1isM13) and (X2 isM23) and (X3 isM33), thenR27=F27(X1,X2,X3),
whereMijdenotes thejth membership function of the ith input,Rk denotes the output of thekth rule, andFk denotes the kth output membership function. The input membershipfunctions are generalized bell type
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