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CN103870833A - Method for extracting and evaluating pavement crack based on concavity measurement - Google Patents

Method for extracting and evaluating pavement crack based on concavity measurement Download PDF

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Publication number
CN103870833A
CN103870833A CN201410125302.1A CN201410125302A CN103870833A CN 103870833 A CN103870833 A CN 103870833A CN 201410125302 A CN201410125302 A CN 201410125302A CN 103870833 A CN103870833 A CN 103870833A
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crack
value
concavity
pixel
point
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CN103870833B (en
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洪汉玉
章秀华
洪梓铭
荆根强
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Wuhan Institute of Technology
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Wuhan Institute of Technology
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Abstract

The invention discloses a method for extracting and evaluating a pavement crack based on concavity measurement. The method mainly comprises the steps that concavity characteristic strength calculation and processing are carried out on a collected pavement crack image through the concavity measurement; a concavity characteristic strength value is enhanced by adopting the local contrast; preliminary noise reduction is carried out through area variance calculation, and statistics and connected domain noise reduction based on geometrical features are carried out on geometrical features of all connected domains of a characteristic strength image processed in a binarization mode; morphological expansion processing and frame extraction are carried out on a result image after geometrical feature noise reduction; statistics is carried out on the geometric sense of the crack in the image after frame extraction, pixel tracking is carried out on a crack target through a depth search algorithm, and a linear target characteristic value obtained through tracking is stored; image information of the crack is converted into graphic data vector information to obtain topological morphological characteristics of the crack, and finally analysis, statistics and description are carried out on the characteristics of the crack. The method can automatically and accurately extract the crack target and carry out analysis, statistics and description on the morphology of the crack.

Description

The pavement crack of estimating based on concavity extracts and assessment method
Technical field
The present invention relates to image processing field, relate in particular to a kind of pavement crack of estimating based on concavity and extract and assessment method.
Background technology
In recent years, along with the development of China Transportation Industry, particularly the construction of highway has obtained development faster, the mileage of highway and heavy goods vehicles quantity are all in quick increase, it is a problem becoming increasingly conspicuous that the road surface profile thereupon causing is deformed into, the analysis in road pavement crack is the important component part of evaluating Pavement Condition, carries out especially the basis of highway scientific maintenance.Crack is repeatedly to travel and roll after generation flow deformation, wearing and tearing, depression through doughnut in road surface, and the often groove of longitudinal band shape producing in driveway wheelpath, is road surface permanent deformation, is made up of the depression of wheelmark and the protuberance of both sides.At present, highway in China maintenance technique for investigation part has realized robotization, but many specific works must, by manually completing, not only be wanted barring traffic, also will drop into a large amount of man power and materials.Manual type efficiency is low, investment large, poor stability, affect traffic, and the precision of data is also difficult to be guaranteed, and along with the development of the hardware technology such as computing machine and image acquisition, automatic collection and the detection technique of pavement crack image are growing.
Pavement crack disease is the Common Diseases type of highway pavement, belongs to two-dimentional wire disease.Highway in China is mainly take bituminous pavement and cement concrete pavement as main, and wherein asphalt pavement crack Damage Types has: be full of cracks, block crack, longitudinal crack, transverse crack etc.Therefore automatic detection of pavement disease is a problem that is not easy solution, is also to improve the problem that highway maintenance detection automatization level must be faced simultaneously.
At present, automatic collection and the storage means of pavement crack image reach its maturity, and the pavement crack image of collection is subject to the impact of many factors, as (1) imaging gray scale inequality; (2) image blurring; (3) shadow problem and white line; (4) irregularity in non-crack, road surface; (5) random noise etc., makes the extraction and quite difficulty of identification in crack in image processing process.
At present, the extracting method in crack has: on pre-service basis, fracture image carries out Threshold segmentation, then extracts the linear feature on image, or adopts Texture classification, finally identifies crack target according to linear feature from former gray level image.
Separately having a kind of method is on figure image intensifying basis, adopts between maximum kind, inter-object distance criterion carries out Threshold segmentation to image, on segmentation result figure, extracts FRACTURE CHARACTERISTICS.
Also having a kind of method is on figure image intensifying basis, carries out image cut apart based on multiscale space model.
In said method, all adopt the dividing method fracture image based on threshold value to process, but thresholding method is very poor to the extraction effect in thinner in figure or distant crack, even miss part crack information, and in result, there is a large amount of noises, can make like this testing result undesirable, not reach the object that pavement crack detects automatically.
Summary of the invention
The technical problem to be solved in the present invention is for road pavement crack extract in prior art not accurate enough, perfect, and the defect that robustness is not strong provides a kind of assessment method that can automatically, accurately extract crack target and carry out fracture morphology analysis.
The technical solution adopted for the present invention to solve the technical problems is:
Provide a kind of pavement crack of estimating based on concavity to extract and assessment method, comprise the following steps:
S101, collection pavement crack image;
S102, to gather pavement crack image be normalized, make the gray-scale value of entire image between 0-255;
S103, extraction concavity characteristic strength: the window of selecting a certain size according to the image after normalized in step S102, the concavity characteristic strength value of the centre coordinate pixel of calculation window, in whole image-region from left to right, moving window from top to bottom, calculate the concavity characteristic measurement value of each coordinate pixel in whole figure, measure value is carried out to threshold process, be less than setting to 0 of threshold value, be more than or equal to the intensity level that is set to of threshold value, obtain concavity characteristic strength figure, and normalize to 0-255;
The enhancing processing of S104, concavity characteristic strength figure: be not 0 point to intensity level in concavity characteristic strength figure, calculate its local contrast, if current some local contrast value is less than setting contrast threshold, the intensity level of current point is set to 0, if be more than or equal to setting threshold, retain initial value; Crack concavity characteristic strength figure after treatment is enhanced;
S105, Local Deviation denoising: utilize Local Deviation method of discrimination to carry out denoising to strengthening pavement crack concavity characteristic strength figure after treatment;
S106, the pavement crack concavity characteristic strength figure after variance denoising is carried out to binary conversion treatment, judge whether the value of pixel is less than the threshold value of a setting, if, be set to 0, if not, be set to 255, obtained the concavity characteristic pattern after binary conversion treatment;
S107, the geometrical property of all connected domains in the concavity characteristic pattern after binary conversion treatment is added up, comprise the number of contained pixel in connected domain, length and the width of connected domain;
S108, the denoising of connected domain geometrical property: the threshold value of setting connected domain length, width and number of pixels, judge in figure whether each geometrical property value in single connected domain is less than the threshold value of setting, if be less than setting threshold, this connected domain pixel value is all set to 0; Otherwise, retain this connected domain; Finally obtain the result figure after geometrical property denoising;
S109, the result figure after geometrical property denoising is carried out to morphological dilations processing;
S110, the crack target after expansion process is carried out to skeletal extraction, become single pixel linear target with topological morphological character;
The geometric sense in crack in figure after S111, statistics skeletal extraction, utilize deep search algorithm, each single pixel linear target is carried out to pixel tracking, preserve and follow the tracks of the linear target eigenwert obtaining, comprise coordinate, branch node coordinate, branch's number of all pixels in each target, length and the width in linear crack, and the shared region area in block crack;
S112, the crack geometric sense information obtaining according to tracking, the image information in crack is converted to graph data Vector Message, obtain the topological morphological feature in crack, analyze, add up, describe and evaluate according to the topological morphological feature fracture geometrical property in this crack.
In method of the present invention, in step S103, selection window specifically comprises:
By in the image after normalized in step S102 a bit as window Selection Center point, select respectively two sizeable wicket A(sizes to be
Figure 2014101253021100002DEST_PATH_IMAGE004
) and large window (size is ), the region in large window outside wicket is B;
In step S103, calculate current point concavity characteristic strength value, comprise the following steps:
1. calculate the mean value of pixel in wicket A
Figure 2014101253021100002DEST_PATH_IMAGE008
;
2. calculate
Figure 63120DEST_PATH_IMAGE008
and the difference in the B of region between other each point value: ;
If 3. , concavity number variable
Figure 2014101253021100002DEST_PATH_IMAGE014
add 1; If
Figure 2014101253021100002DEST_PATH_IMAGE016
, a concavity number variable
Figure 75070DEST_PATH_IMAGE014
remain unchanged;
Figure 2014101253021100002DEST_PATH_IMAGE018
4. in the B of region, total number of pixels is designated as
Figure 2014101253021100002DEST_PATH_IMAGE020
;
5. calculate the concavity number factor
Figure 2014101253021100002DEST_PATH_IMAGE022
;
6. to all satisfying condition in window difference
Figure 2014101253021100002DEST_PATH_IMAGE026
be averaging concavity intensity level
Figure 2014101253021100002DEST_PATH_IMAGE028
If 7. each concavity characteristic measurement value of current point satisfies condition simultaneously
Figure 2014101253021100002DEST_PATH_IMAGE030
and
Figure 2014101253021100002DEST_PATH_IMAGE032
, current some intensity assignment is
Figure 2014101253021100002DEST_PATH_IMAGE034
, otherwise be set to 0, obtain current point after treatment
Figure 180167DEST_PATH_IMAGE002
concavity characteristic strength value.
In method of the present invention, step S104 specifically comprises:
(1) set sizeable window, the point that concavity characteristic strength figure intermediate value is greater than 0 is aimed at the center of window, and in former gray-scale map, confines the image-region in this window respective coordinates region;
(2) in the concavity characteristic strength figure in window, statistical value is not 0 number of pixels
Figure 2014101253021100002DEST_PATH_IMAGE036
;
(3), in the former gray-scale map in window, be not 0 grey scale pixel value summation corresponding to coordinate to (2) step intermediate value
Figure 2014101253021100002DEST_PATH_IMAGE038
, coordinate pixel corresponding in strength characteristic figure is not 0;
(4) the interior value of calculation window is not 0 zone leveling value
Figure 2014101253021100002DEST_PATH_IMAGE040
;
(5) number of pixels that in the concavity characteristic strength figure in window, statistical value is 0
Figure 2014101253021100002DEST_PATH_IMAGE042
;
(6) in the former gray-scale map in window, the grey scale pixel value summation that the coordinate that is 0 to (5) step intermediate value is corresponding
Figure 2014101253021100002DEST_PATH_IMAGE044
,
Figure 2014101253021100002DEST_PATH_IMAGE046
coordinate pixel corresponding in characteristic pattern is 0;
(7) the zone leveling value that in calculation window, value is 0 ;
(8) calculate the ratio of two the zone leveling value difference values in current some place:
Figure 2014101253021100002DEST_PATH_IMAGE050
;
(9) judge ratio
Figure 2014101253021100002DEST_PATH_IMAGE052
if this ratio is less than a setting threshold, current point value is set to 0; If be more than or equal to setting threshold, retain current point value;
(10) window at whole figure from left to right, slides from top to bottom, and window center to aim at intensity map intermediate value be not 0 point at every turn, obtain contrast concavity characteristic strength after treatment figure, and be normalized to 0-255,
In method of the present invention, calculate the variance of crack concavity characteristic strength figure ;
Calculate the variance yields of the each connected domain of crack concavity characteristic strength figure
Figure 2014101253021100002DEST_PATH_IMAGE056
;
Calculate the poor of the variance yields of each connected domain and whole figure variance yields:
Figure 2014101253021100002DEST_PATH_IMAGE058
.If
Figure 2014101253021100002DEST_PATH_IMAGE060
, retain this connected domain; If
Figure 2014101253021100002DEST_PATH_IMAGE062
, remove whole connected domain.
In method of the present invention, in step S111, utilize deep search algorithm, each single pixel linear target carried out to pixel tracking and specifically comprise the following steps:
A) in whole figure, from left to right point by point search is not 0 pixel from top to bottom, judges whether it is end points, and the starting point using first end points finding as first tree crack is accessing points with this point of tense marker, sets number of pixels counter and adds 1;
B) centered by initial end points, travel through 8 neighborhoods of this pixel, mark is not wherein 0 pixel is accessing points, tree number of pixels counter adds 1;
C) continue traversal upper one 8 neighborhood territory pixels of gauge point, if in its 8 neighborhood point, be not 0 and unlabelled pixel only have one, set number of pixels counter and add 1, mark current pixel point; If value be not 0 and unlabelled pixel have 2 and more than, according to priority determine that point sets pixel impact point for next, rest of pixels point coordinate is stacked, and mark current pixel point, defining current point is node, node counts device adds 1;
D) get back to the c) step, continue search, until look for complete the whole pixels of tree-shaped crack trunk;
E) by the mode of first in first out, node is popped, the starting point using node as access, repeated execution of steps c), until accessed whole nodes;
F) the trunk pixel number of the crack tree that statistics has been accessed, branch node number and coordinate, form crack topology information, realized quantitative calculating and the statistics of pavement crack;
Continue to search in the drawings initial end points, after finding, get back to the b) step, the related data of adding up next tree-shaped crack, forms topology information; Until have access to all slits Pixel Information in view picture figure, follow the tracks of and finish.
The beneficial effect that the present invention produces is: fracture image of the present invention carries out single pixel and follows the tracks of detection, and the crack object pixel obtaining is corresponding with the center line in true crack, and crack extract and accurate positioning, be not subject to the interference of road sign, shade; By deep search algorithm, realize quantitative calculating and the statistics of pavement crack, for follow-up pavement patching provides quantification information and Data support; Crack of the present invention concavity characteristic measurement calculates simple, and computational complexity is low, only has plus and minus calculation, the characteristic strength obtaining is obvious, elimination and the denoising of pseudo-characteristic are simple and convenient, and the processing time is short, meet the time requirement of express highway pavement Crack Detection to computing; Adopt in addition the method that the present invention proposes to test a large amount of pavement images that gather, program is stable, and adaptivity is good, strong robustness, and all picture processings, without manual intervention, have been obtained satisfied pavement crack and have been detected and evaluating result.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing:
Fig. 1 is that the pavement crack estimated based on concavity of the embodiment of the present invention extracts and the process flow diagram of assessment method;
Fig. 2 is the pavement crack gray level image that the embodiment of the present invention gathers, and normalization sets to 0-255;
Fig. 3 is that embodiment of the present invention pavement crack concavity is estimated calculating schematic diagram;
Fig. 4 is that the embodiment of the present invention is carried out concavity to Fig. 2 and estimated the characteristic strength figure calculating;
Fig. 5 is that the local contrast of embodiment of the present invention concavity intensity level is calculated schematic diagram;
Fig. 6 carries out to Fig. 2 the result figure that contrast computing obtains for the embodiment of the present invention on Fig. 4 basis;
Fig. 7 is the result that the embodiment of the present invention adopts Local Deviation Fig. 6 to be carried out to denoising;
Fig. 8 is the binaryzation result figure of Fig. 7;
Fig. 9 utilizes connected domain geometrical property to carry out the result of denoising on Fig. 8 basis;
Figure 10 is the result of Fig. 9 being carried out to morphological dilations processing;
Figure 11 is the result of Figure 10 being carried out to skeletal extraction;
Figure 12 is that the geometric configuration of embodiment of the present invention fracture is described and statistics schematic diagram.
 
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
The pavement crack that the embodiment of the present invention is estimated based on concavity extracts with assessment method and mainly comprises the following steps:
S101, collection pavement crack image;
S102, to gather pavement crack image be normalized, make the gray-scale value of entire image between 0-255, as shown in Figure 2;
S103: extract concavity characteristic strength: the window of selecting a certain size according to the image after normalized in step S102, the concavity characteristic strength value of the centre coordinate pixel of calculation window, in whole image-region from left to right, moving window from top to bottom, calculate the concavity characteristic measurement value (comprising concavity intensity level and the concavity number factor) of each coordinate pixel in whole figure, measure value is carried out to threshold process, be less than setting to 0 of threshold value, be more than or equal to the intensity level that is set to of threshold value.Obtain concavity characteristic strength figure, and normalize to 0-255;
In one embodiment of the present of invention, as shown in Figure 2, take a pixel wherein as the current point that calculates concavity intensity is as example.Using this point as window Selection Center point, select respectively two sizeable wicket A(sizes to be
Figure 180057DEST_PATH_IMAGE004
) and large window (size is
Figure 917069DEST_PATH_IMAGE006
), the region in large window outside wicket is B; As shown in Figure 3;
In one embodiment of the present of invention, to current point
Figure 440454DEST_PATH_IMAGE002
, calculate its concavity intensity level, adopt following steps to calculate:
1. calculate the mean value of pixel in wicket A
Figure 870299DEST_PATH_IMAGE008
.
2. calculate and the difference in the B of region between other each point value:
Figure 200097DEST_PATH_IMAGE010
;
If 3.
Figure 843568DEST_PATH_IMAGE012
, concavity number variable
Figure 178734DEST_PATH_IMAGE014
add 1; If
Figure 969973DEST_PATH_IMAGE016
, a concavity number variable
Figure 48787DEST_PATH_IMAGE014
remain unchanged;
4. in the B of region, total number of pixels is designated as
Figure 318412DEST_PATH_IMAGE020
;
5. calculate the concavity number factor
Figure 580635DEST_PATH_IMAGE022
;
6. to all satisfying condition in window difference
Figure 815624DEST_PATH_IMAGE026
be averaging concavity intensity level
If 7. each concavity characteristic measurement value of current point (comprising concavity intensity level and the concavity number factor) satisfies condition simultaneously
Figure 258424DEST_PATH_IMAGE030
and
Figure 679041DEST_PATH_IMAGE032
, current some intensity assignment is
Figure 151610DEST_PATH_IMAGE034
, otherwise be set to 0, obtain current point after treatment concavity characteristic strength value.
Moving window from top to bottom from left to right in whole image-region, obtains the concavity characteristic strength value of each coordinate pixel in whole figure;
After above-mentioned processing, obtain the concavity characteristic strength figure of former gray-scale map, as shown in Figure 4.
S104, meet step S103, on above-mentioned processing basis, concavity characteristic strength figure is carried out to region contrast and strengthen and process, step is as follows:
[1] set size to fit window, the point that concavity characteristic strength figure intermediate value is greater than 0 is aimed at the center of window, and in former gray-scale map, confines the image-region in this window respective coordinates region;
[2] in the concavity characteristic strength figure in window, statistical value is not 0 number of pixels
Figure 3340DEST_PATH_IMAGE036
;
[3], in the former gray-scale map in window, be not 0 grey scale pixel value summation corresponding to coordinate to (2) step intermediate value ,
Figure 289145DEST_PATH_IMAGE002
coordinate pixel corresponding in strength characteristic figure is not 0;
[4] the interior intensity level of calculation window is not 0 zone leveling value
Figure 635812DEST_PATH_IMAGE040
;
[5] number of pixels that in the concavity characteristic strength figure in window, statistical value is 0
Figure 48339DEST_PATH_IMAGE042
;
[6] in the former gray-scale map in window, to the grey scale pixel value summation that in (5) step, intensity level is 0 ,
Figure 257921DEST_PATH_IMAGE046
the former figure gray-scale value that is 0 in intensity map intermediate value;
[7] the zone leveling value that in calculation window, value is 0
Figure 762108DEST_PATH_IMAGE048
;
[8] calculate the ratio of two the zone leveling value difference values in current some place:
Figure 661931DEST_PATH_IMAGE050
;
[9] judgement ratio above, if this ratio is less than a setting threshold, is set to 0 by current point value; If be more than or equal to setting threshold, retain current point value;
[10] window at whole figure from left to right, slides from top to bottom, and window center to aim at intensity map intermediate value be not 0 point at every turn, obtain contrast concavity characteristic strength after treatment figure, and be normalized to 0-255, result as shown in Figure 6.
S105, meet step S104, to above-mentioned crack concavity characteristic strength figure, adopt variance denoising method to remove pseudo-target;
(1) variance of calculating concavity intensity map (being crack concavity characteristic strength figure)
Figure 290358DEST_PATH_IMAGE054
;
(2) variance yields of each connected domain in calculating concavity intensity map ;
(3) calculate the poor of the variance yields of each connected domain and whole figure variance yields:
Figure 952601DEST_PATH_IMAGE058
.If
Figure 152769DEST_PATH_IMAGE060
, retain this connected domain; If
Figure 522570DEST_PATH_IMAGE062
, remove whole connected domain;
(4) obtain the result after Variance feature denoising, as shown in Figure 7;
S106, meet step S105, to the pavement crack concavity characteristic strength figure binaryzation after variance denoising, judge whether the value of pixel is 0, be if so, set to 0, if not, be set to 255, the concavity obtaining after binary conversion treatment is estimated figure, as shown in Figure 8;
S107, the geometrical property of each connected domain in view picture figure (the concavity intensity map after binary conversion treatment) is added up, comprise the number of contained pixel in each connected domain, the length of connected domain and width, and whole mean value of pixel grey scales in each connected domain;
S108, the denoising of connected domain geometrical property: set the threshold value of connected domain length, width and number of pixels, judge in figure in single connected domain that whether each eigenwert is less than the threshold value of setting, if be less than setting threshold, is set to 0 by this connected domain pixel value; Otherwise, retain this connected domain.As set connected domain length threshold
Figure DEST_PATH_IMAGE066
if, connected domain length in figure
Figure DEST_PATH_IMAGE068
be less than setting threshold, this connected domain pixel value be set to 0; Otherwise, retain this connected domain; Obtain the result images after geometrical property denoising, as shown in Figure 9;
S109, the result figure after geometrical property denoising is carried out to expansion process, the results are shown in Figure 10;
S110, the crack target after expansion process being carried out to skeletal extraction, become single pixel linear target with topological morphological character, as shown in figure 11, is skeletal extraction result;
The geometric sense in crack in figure after S111, statistics skeletal extraction.Utilize deep search algorithm, each crack is carried out to pixel tracking, preserve the coordinate of pixel in each target, branch node coordinate, branch's number, available schematic diagram Figure 12 describes.In one embodiment of the present of invention, concrete searching algorithm step is as follows:
A), in whole figure, from left to right point by point search is not 0 pixel from top to bottom, judges whether it is end points, starting point using first end points finding as first tree crack, as A point in Figure 12, be accessing points with this point of tense marker, tree number of pixels counter adds 1;
B) centered by initial end points, travel through 8 neighborhoods of this pixel, mark is not wherein 0 pixel is accessing points, tree number of pixels counter adds 1;
C) continue traversal upper one 8 neighborhood territory pixels of gauge point, if in its 8 neighborhood point, be not 0 and unlabelled pixel only have one, set number of pixels counter and add 1, mark current pixel point; If value be not 0 and unlabelled pixel have 2 and more than, according to priority determine that point sets pixel impact point for next, rest of pixels point coordinate is stacked, and mark current pixel point, defining current point is node, node counts device adds 1;
D) get back to the 3. step, continue search, until look for complete the whole pixels of tree-shaped crack trunk;
E) by the mode of first in first out, node is popped, the starting point using node as access, repeated execution of steps 3., until accessed whole nodes;
F) the trunk pixel number of the crack tree that statistics has been accessed, branch node number and coordinate, form topology information;
G) continue to search in the drawings initial end points, after finding, get back to the 2. step, the related data of adding up next tree-shaped crack, forms topology information; Until have access to all slits Pixel Information in view picture figure, follow the tracks of and finish.
S112, meet step S111, the linear target eigenwert obtaining according to tracking, the image information in crack is converted to graph data Vector Message, obtain the topological morphological feature in crack, fracture characteristic is analyzed, adds up, is described and evaluates, and data is submitted to highway administration department and carry out decision-making.
Compared with existing other pavement crack image detection algorithm, the method that the present invention proposes has the following advantages:
1. accuracy: fracture image of the present invention carries out single pixel to be followed the tracks of and detect, the crack object pixel obtaining is corresponding with the center line in true crack, crack extract and accurate positioning, and be not subject to the interference of road sign, shade;
2. quantification: the algorithm of chain code following is used in the analysis of processing fracture morphology geometric properties, has realized quantitative calculating and the statistics of pavement crack, for follow-up pavement patching provides quantification information and Data support;
3. rapidity and high efficiency: crack of the present invention concavity characteristic measurement calculates simple, and computational complexity is low, only has plus and minus calculation, and the characteristic strength obtaining is obvious, and elimination and the denoising of pseudo-characteristic are simple and convenient.On multi-purpose computer, every width image is no more than 0.5 second working time, uses special tool control computer to process, and the processing time is in 0.3 second, meets the time requirement of express highway pavement Crack Detection to computing;
4. adaptivity and robustness are good: adopt the method that the present invention proposes to test a large amount of pavement images that gather, program is stable, and adaptivity is good, strong robustness, all picture processings, without manual intervention, have been obtained satisfied pavement crack and have been detected effect.
Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improvement and conversion all should belong to the protection domain of claims of the present invention.

Claims (5)

1. the pavement crack of estimating based on concavity extracts and an assessment method, it is characterized in that, comprises the following steps:
S101, collection pavement crack image;
S102, to gather pavement crack image be normalized, make the gray-scale value of entire image between 0-255;
S103, extraction concavity characteristic strength: the window of selecting a certain size according to the image after normalized in step S102, the concavity characteristic strength value of the centre coordinate pixel of calculation window, in whole image-region from left to right, moving window from top to bottom, calculate the concavity characteristic measurement value of each coordinate pixel in whole figure; Concavity characteristic measurement value is carried out to threshold process, be less than setting to 0 of threshold value, be more than or equal to the intensity level that is set to of threshold value, obtain concavity characteristic strength figure, and normalize to 0-255;
The enhancing processing of S104, concavity characteristic strength figure: be not 0 point to intensity level in concavity characteristic strength figure, calculate its local contrast, if current some local contrast value is less than setting contrast threshold, the intensity level of current point is set to 0, if be more than or equal to setting threshold, retain initial value; Crack concavity characteristic strength figure after treatment is enhanced;
S105, Local Deviation denoising: utilize Local Deviation method of discrimination to carry out denoising to strengthening pavement crack concavity characteristic strength figure after treatment;
S106, the pavement crack concavity characteristic strength figure after variance denoising is carried out to binary conversion treatment, judge whether the value of pixel is less than the threshold value of a setting, if, be set to 0, if not, be set to 255, obtained the concavity characteristic pattern after binary conversion treatment;
S107, the geometrical property of all connected domains in the concavity characteristic pattern after binary conversion treatment is added up, comprise the number of contained pixel in connected domain, length and the width of connected domain;
S108, the denoising of connected domain geometrical property: the threshold value of setting connected domain length, width and number of pixels, judge in figure whether each geometrical property value in single connected domain is less than the threshold value of setting, if be less than setting threshold, this connected domain pixel value is all set to 0; Otherwise, retain this connected domain; Finally obtain the result figure after geometrical property denoising;
S109, the result figure after geometrical property denoising is carried out to morphological dilations processing;
S110, the crack target after expansion process is carried out to skeletal extraction, become single pixel linear target with topological morphological character;
The geometric sense in crack in figure after S111, statistics skeletal extraction, utilize deep search algorithm, each single pixel linear target is carried out to pixel tracking, preserve and follow the tracks of the linear target eigenwert obtaining, comprise coordinate, branch node coordinate, branch's number of all pixels in each target, length and the width in linear crack, and the shared region area in block crack;
S112, the crack geometric sense information obtaining according to tracking, the image information in crack is converted to graph data Vector Message, obtain the topological morphological feature in crack, analyze, add up, describe and evaluate according to the topological morphological feature fracture geometrical property in this crack.
2. method according to claim 1, is characterized in that,
In step S103, selection window specifically comprises: by the image after normalized in step S102 a bit
Figure 2014101253021100001DEST_PATH_IMAGE002
as window Selection Center point, select respectively two sizeable wicket A and large window, wherein wicket size is
Figure 2014101253021100001DEST_PATH_IMAGE004
, large window size is
Figure 2014101253021100001DEST_PATH_IMAGE006
, the region in large window outside wicket is B;
In step S103, calculate current point
Figure 301525DEST_PATH_IMAGE002
concavity characteristic strength value, comprise the following steps:
1. calculate the mean value of pixel in wicket A
Figure 2014101253021100001DEST_PATH_IMAGE008
;
2. calculate
Figure 280983DEST_PATH_IMAGE008
and the difference in the B of region between other each point value: ;
If 3.
Figure 2014101253021100001DEST_PATH_IMAGE012
, concavity number variable
Figure 2014101253021100001DEST_PATH_IMAGE014
add 1; If
Figure 2014101253021100001DEST_PATH_IMAGE016
, a concavity number variable
Figure 873769DEST_PATH_IMAGE014
remain unchanged;
Figure 2014101253021100001DEST_PATH_IMAGE018
4. in the B of region, total number of pixels is designated as
Figure 2014101253021100001DEST_PATH_IMAGE020
;
5. calculate the concavity number factor
Figure 2014101253021100001DEST_PATH_IMAGE022
;
6. to all satisfying condition in window
Figure 2014101253021100001DEST_PATH_IMAGE024
difference
Figure 2014101253021100001DEST_PATH_IMAGE026
be averaging concavity intensity level
Figure 2014101253021100001DEST_PATH_IMAGE028
If 7. each concavity characteristic measurement value of current point satisfies condition simultaneously and
Figure 2014101253021100001DEST_PATH_IMAGE032
, current some intensity assignment is
Figure 2014101253021100001DEST_PATH_IMAGE034
, otherwise be set to 0, obtain current point after treatment
Figure 708126DEST_PATH_IMAGE002
concavity characteristic strength value.
3. method according to claim 1, is characterized in that, step S104 specifically comprises:
Set sizeable window, the point that concavity characteristic strength figure intermediate value is greater than 0 is aimed at the center of window, and in former gray-scale map, confines the image-region in this window respective coordinates region;
In concavity characteristic strength figure in window, statistical value is not 0 number of pixels
Figure 2014101253021100001DEST_PATH_IMAGE036
;
In former gray-scale map in window, be not 0 grey scale pixel value summation corresponding to coordinate to (2) step intermediate value
Figure 2014101253021100001DEST_PATH_IMAGE038
, coordinate pixel corresponding in strength characteristic figure is not 0;
In calculation window, value is not 0 zone leveling value
Figure 2014101253021100001DEST_PATH_IMAGE040
;
The number of pixels that in concavity characteristic strength figure in window, statistical value is 0
Figure 2014101253021100001DEST_PATH_IMAGE042
;
In former gray-scale map in window, the grey scale pixel value summation that the coordinate that is 0 to (5) step intermediate value is corresponding
Figure 2014101253021100001DEST_PATH_IMAGE044
,
Figure DEST_PATH_IMAGE046
coordinate pixel corresponding in characteristic pattern is 0;
The zone leveling value that in calculation window, value is 0
Figure DEST_PATH_IMAGE048
;
Calculate the ratio of two the zone leveling value difference values in current some place:
Figure DEST_PATH_IMAGE050
;
Judge ratio if this ratio is less than a setting threshold, current point value is set to 0; If be more than or equal to setting threshold, retain current point value;
Window at whole figure from left to right, slides from top to bottom, and window center to aim at intensity map intermediate value be not 0 point at every turn, obtain contrast concavity characteristic strength after treatment figure, and be normalized to 0-255.
4. method according to claim 1, is characterized in that, step S105 specifically comprises the following steps:
Calculate the variance of crack concavity characteristic strength figure
Figure DEST_PATH_IMAGE054
;
Calculate the variance yields of the each connected domain of crack concavity characteristic strength figure ;
Calculate the poor of the variance yields of each connected domain and whole figure variance yields:
Figure DEST_PATH_IMAGE058
;
If
Figure DEST_PATH_IMAGE060
, retain this connected domain; If
Figure DEST_PATH_IMAGE062
, remove whole connected domain.
5. method according to claim 1, is characterized in that, utilizes deep search algorithm in step S111, each single pixel linear target is carried out to pixel tracking and specifically comprise the following steps:
In whole figure, from left to right point by point search is not 0 pixel from top to bottom, judges whether it is end points, and the starting point using first end points finding as first tree crack is accessing points with this point of tense marker, sets number of pixels counter and adds 1;
Centered by initial end points, travel through 8 neighborhoods of this pixel, mark is not wherein 0 pixel is accessing points, tree number of pixels counter adds 1;
Continue traversal upper one 8 neighborhood territory pixels of gauge point, if in its 8 neighborhood point, be not 0 and unlabelled pixel only have one, set number of pixels counter and add 1, mark current pixel point; If value be not 0 and unlabelled pixel have 2 and more than, according to priority determine that point sets pixel impact point for next, rest of pixels point coordinate is stacked, and mark current pixel point, defining current point is node, node counts device adds 1;
Get back to the c) step, continue search, until look for complete the whole pixels of tree-shaped crack trunk;
By the mode of first in first out, node is popped, the starting point using node as access, repeated execution of steps c), until accessed whole nodes;
The trunk pixel number of the crack tree that statistics has been accessed, branch node number and coordinate, form topology information;
Continue to search in the drawings initial end points, after finding, get back to the b) step, the related data of adding up next tree-shaped crack, forms topology information; Until have access to all slits Pixel Information in view picture figure, follow the tracks of and finish.
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