CN106570887A - Adaptive Mean Shift target tracking method based on LBP features - Google Patents

Adaptive Mean Shift target tracking method based on LBP features Download PDF

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CN106570887A
CN106570887A CN201610965929.7A CN201610965929A CN106570887A CN 106570887 A CN106570887 A CN 106570887A CN 201610965929 A CN201610965929 A CN 201610965929A CN 106570887 A CN106570887 A CN 106570887A
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target
candidate
tracking
represent
pixel
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唐晨
程佳佳
苏永钢
李碧原
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Tianjin University
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F18/00Pattern recognition
    • G06F18/20Analysing
    • G06F18/22Matching criteria, e.g. proximity measures
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/10Image acquisition modality
    • G06T2207/10016Video; Image sequence
    • 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
    • G06T2207/30221Sports video; Sports image

Abstract

The invention relates to the technical fields of computer vision and target tracking, and aims to solve the problem on how to ensure the robustness of target tracking in different background interference situations, improve the robustness and adaptability of an algorithm and effectively overcome constant change of the dimension and direction of a target in the process of tracking. According to the technical scheme employed in the invention, an adaptive Mean Shift target tracking method based on LBP features comprises the following steps: (1) generation of a target model; (2) similarity measurement: the similarity between the target model and a target candidate model is measured with a Bhattacharyya coefficient; and (3) target dimension and direction estimation: Mean shift iteration is performed on a target area to make the target area converge to the spatial location of a candidate target, matrix decomposition is performed on a target candidate area weight map integrating texture and color features, and the dimension and direction of the target candidate area are calculated through matrix analysis. The method is mainly used in target tracking occasions.

Description

With reference to LBP feature adaptive M ean Shift method for tracking target
Technical field
The present invention relates to computer vision and target following technical field, more particularly to a kind of two-dimentional local binary spy of joint Levy Mean Shift method for tracking target adaptive with the dimension of color histogram.
Background technology
Computer vision is a new branch of science developed in recent years, and its research contents covers intelligent monitoring system The fields such as system, robot visual guidance, man-machine interaction, object dimensional reconstruction, automatic Pilot.In numerous researchs of computer vision In field, the extensive concern of domestic and international academia and industrial quarters is received based on the motion target tracking of image sequence, in intelligence Monitoring, robot navigation, intelligent transportation, video content analysis with understand etc. field there is important using value, be one not The key technology that can or lack.
For the research of image sequence motion target tracking, a large amount of outstanding track algorithms have been emerged in large numbers.Numerous outstanding In track algorithm, the Moving Target Tracking Algorithm based on Mean Shift is little with its amount of calculation, insensitive to target rotation, deformation The advantages of and get the attention, become current goal track field study hotspot.2003, Comaniciu et al. will Mean shift algorithms are incorporated into target tracking domain, it is proposed that the motion mesh based on Mean shift with milestone significance Mark track algorithm (see document [1,2]).Hereafter, some defects for existing for the method, domestic and international researcher are proposed in a large number Outstanding innovatory algorithm (see document [3]~[8]).
Although original Mean shift target tracking algorisms have amount of calculation little, to target distortion, rotation, partial occlusion Insensitive the advantages of, however, some limitations of the algorithm are also obvious:
(1) using color histogram as the appearance features of target, it is impossible to all information comprising target;And color characteristic pair Illumination variation is sensitive, in the case of illumination variation, tracking target easy to lose;Additionally, in target and the close situation of background color Under, it is impossible to effectively identify tracking target (see document [3] and [4]).
(3) cannot effectively estimate target scale and direction (see document [5]).
(2) lack effective object module more New Policy (see document [6] and [7]).
(4) background clutter cannot be overcome to disturb this defect, when more clutter occurs in background, tracking target easy to lose (see Document [8]).
List of references:
[1]Comaniciu D,Ramesh V,Meer P.Real-time tracking of non-rigid objects using Mean shift[C].IEEE conference on Computer Vision and Pattern Recognition.2000:142-149
[2]Comaniciu D,Ramesh V,Meer P.Kernel-based object tracking[J].IEEE trans on pattern Analysis and Machine Intelligence,2003,25(5):564-575
[3]Leichter I,Lindenbaum M,Rivlin E.Mesn Shift tracking with multiple reference color histograms[J].Computer Vision and Image Understanding,2010, 114(3):400-408
[4]Tan Xiao-yang,Triggs B.Enhanced Local Texture Feature Sets for Face Recognition Under Difficult Lighting Conditions[J].IEEE Transaction on Image Processing,2010,19(6):1635-1650
[5]Tomas Vojir,Jana Noskova,Jiri Matas.Robust scale-adaptive mean- shift for tracking[J].Pattern Recognition Letters,2014,49(1):250-258
[6]Huiyu Zhou,Yuan Yuan,Chunmei Shi.Object tracking using SIFT features and mean shift[J].Computer Vision and Image Understanding,2009,113 (3):345-352
[7]Nan Luo,Quansen Sun,Qiang Chen.A Novel Tracking Algorithm via Feature Points Matching[J].PLoS ONE,2015
[8]Fouad Bousetouane,Lynda Dib,Hichem Snoussi.Improved mean shift integrating texture and color features for robust real time object tracking [J],2013,29:155-170。
The content of the invention
To overcome the deficiencies in the prior art, it is contemplated that realize can guarantee under different background interference cases target with The robustness of track, improves the robustness and adaptability of algorithm, constantly becomes efficiently against target scale during tracking and direction The problem of change.The technical solution used in the present invention is, with reference to LBP feature adaptive M ean Shift method for tracking target, step It is as follows:
(1) object module is generated:
The joint histogram that object module is made up of with color characteristic the local binary feature of image describing, that is, utilize by The color in mask that local binary patterns are formed and textural characteristics build the mesh of joint texture-color characteristic describing target Mark model;
(2) similarity measurement:
The similarity between object module and target candidate model is weighed using Bhattacharyya coefficients, Bhattacharyya coefficients represent two vectors and between angle cosine value, its value is bigger, represents object module and waits with target Modeling type is more similar, calculates the Bhattacharyya coefficients of above-mentioned object module and target candidate model first, and specifies certain Measurement criterion so as to the similarity highest under the criterion;
(3) target scale direction estimation:
During tracking, Mean shift iteration is carried out first to target area so as to converge to the sky of candidate target Between at position, the object candidate area weight map of the joint texture-color characteristic to generating in (1) carries out matrix decomposition, utilizes Matrix analyses are calculating yardstick and the direction of object candidate area.
Local binary patterns LBP operators with grey scale invariance and rotational invariance are obtained by following model :
Wherein, represent gcThe pixel value of correspondence window center point, P represent (xc,yc) pixel around window center point, gpCentered on pixel value in vertex neighborhood, R represents the scope of neighborhood, and riv2 represents invariable rotary equivalent formulations, U (LBPP,R) For defining for invariable rotary pattern LBP operator, its value≤2, represent and light from starting point 0, calculate at adjacent 2 points with central point picture The difference of function s (x) of element value, travels through P pixel successively:
Wherein, gP-1Represent the pixel value of pixel P-1 in neighborhood, g0Represent the pixel value of starting point in neighborhood;With S (gP- gc+ a) replace S (gP-gc), a is to make up the little threshold value for setting of pixel fluctuation in flat site;Also, | a | is bigger, pixel ripple Dynamic permissible value is bigger;
Local binary feature LBP of effectively joint objective is comprised the following steps that with color characteristic:
There are 9 uniform texture patterns, each LBP texture pattern can be considered as a microtexture primitive,In topography's block that operator is detected, feature is included a little, flat site, edge, the starting point and terminal of line segment, In object representation, above-mentioned microtexture primitive includes angle point, edge, line segment, and referred to as main target pattern represents target Most of feature, and point, plane domain are referred to as secondary target pattern, are the secondary textures of target;By equation below To extract most of target pattern of target:
In operator, the secondary target pattern of the correspondence of labelling 0,1,7,8, labelling 9 do not correspond to target pattern.Cause This, main target pattern is marked with:2~6, the main LBP patterns of target are extracted by formula (7), then the face of joint image Color characteristic describes target, is built into the joint histogram of 8 × 8 × 8 × 5 four-dimensional joint texture-color.
Object module adopts Bhattacharyya coefficients ρ (y) to weigh with the similarity of candidate target model, i.e.,
Wherein, y represents candidate target region center, and u=1,2...m represent any one color index, Object module and candidate target model are represented respectively;quAnd puY () is illustrated respectively in target area And in candidate target region probability distribution rectangular histogram feature u probability;Bhattacharyya coefficients ρ (y) defines tracking target With the similarity of candidate target, additionally, defining metric function d (y), which is represented between tracking target and candidate target model Distance:
Bhattacharyya is bigger, and object module is more similar to candidate target, to ρ [p (y) q] in pu(y0) place carries out Thailand Series expansion is strangled, high-order term is removed, only retains single order expansion, the linear approximation formula for obtaining ρ [p (y) q] is as follows:
y0Represent the center of target candidate model in previous frame, pu(yo) represent previous frame target candidate model;Will Object module is substituted into candidate target model and can be obtained:
Wherein,
In formula (11), Section 1 is unrelated with y, and Section 2 represents the Density Estimator at candidate target region central point y, Wherein each pixel xiWeight w (xi) represent.So find best candidate target problem translate into searching probability it is close The problem of degree function local extremum position, and above formula (11) is maximized completing by the method for Mean shift iteration, evenObtain the iteration form of Mean shift:
Wherein, g (x)=- k'(x), with previous frame target location y0For initial value, the y in above formula is iterated to calculate, until receiving Hold back or reach the maximum iteration time of setting.
Target scale direction estimation comprises the concrete steps that, estimates to track using the square information of candidate target region weight map In journey, the dimension change of target, is carried out the deformation of adaptive targets, in previous frame, is sought using Mean shift iterative algorithms Optimal objective region is found, as current tracking result, the zeroth order square M in the region is then calculated using following formula00
w(xi) represent each pixel xiThe weight at place, n are the number of pixel in target area;Utilize Bhattacharyya coefficients define following formula correcting the error caused by zeroth order square:
A=c (ρ) M00 (15)
C (ρ) is the monotonically increasing function related to Bhattacharyya coefficient ρ, and its value is between 0~1:
Wherein, σ is adjustable parameter.When ρ (0~1) reduces, c (ρ) (0~1) also reduces;I.e. with object module and time Model similarity is selected to reduce, M00Bigger than the area in real goal region, i.e., error is bigger;
The center of next frame object candidate area, yardstick and direction, by the first order and second order moments to weight map Carry out matrix analyses to obtain, first moment M is calculated to weight map10、M01With second moment M20、M02、M11Difference is as follows:
Wherein, (xi,1,xi,2) for the coordinate of pixel i, and the center of next frame candidate target region is by above-mentioned one The ratio of rank square and zeroth order square is tried to achieve:
Wherein, centers of the y for next frame candidate target region,Represent the coordinate of center y;Equally, two The square information of rank square can be used to describe the shape of target area and direction, calculate the ratio and centre bit of second moment and zeroth order square Put coordinateThe difference of two squares, respectively μ20μ11μ02
To analyze scale size and the direction of target area, μ2002, μ11Write covariance matrix Cov, and to association side Difference matrix carries out singular value decomposition:
Wherein,
U, S carry out two matrixes after singular value decomposition for covariance matrix, wherein, (u11,u21)T(u12,u22)TPoint The direction of two axles of target in object candidate area is not represented, the direction of target can be obtained by the angle between major axis and trunnion axis Go out, additionally, λ12For the eigenvalue of covariance matrix Cov, its ratio is identical with the ratio of target area major and minor axis, i.e. λ12 =a/b, introduces scale factor k so that a=k λ1, b=k λ2, then the area of target area be:π ab=π (k λ1)(kλ2)=A, So, the major and minor axis (a, b) of target area are respectively:
Thus, the yardstick of target and direction during tracking just are estimated.
The characteristics of of the invention and beneficial effect are:
In the image sequence method for tracking target that the present invention is provided, the introducing of local binary feature (improved LBP) is caused The description of object module is no longer limited to solid color feature, meanwhile, on this basis, square is carried out to the weight map of target area Battle array is decomposed, using going square information effectively to estimate target scale and direction, therefore, the image sequence target following side that the present invention is provided Method all has higher reliability and robustness for the image sequence target following under illumination condition and target deformation.
Description of the drawings:
Fig. 1 provides the tracking block schematic illustration of track algorithm for the present invention.
The part tracking result of track algorithm that Fig. 2 (a) is provided for the present invention, from left to right, from top to bottom respectively the 5th, the tracking result of 10,13,21,24,31 frames;
Part tracking results of the Fig. 2 (b) for SOAMST track algorithms, from left to right, from top to bottom the respectively the 5th, 10, 13rd, the tracking result of 21,24,31 frames;
The part tracking result of track algorithm that Fig. 3 (a) is provided for the present invention, from left to right, from top to bottom respectively the 4th, the tracking result of 22,31,45,49,51 frames;
Part tracking results of the Fig. 3 (b) for SOAMST track algorithms, from left to right, from top to bottom the respectively the 4th, 22, 31st, the tracking result of 45,49,51 frames;
The part tracking result of track algorithm that Fig. 4 (a) is provided for the present invention, from left to right, from top to bottom respectively the 5th, the tracking result of 10,13,21,24,31 frames;
Part tracking results of the Fig. 4 (b) for SOAMST track algorithms, from left to right, from top to bottom the respectively the 5th, 10, 13rd, the tracking result of 21,24,31 frames.
Specific embodiment
The invention provides the adaptive Mean of dimension of a kind of combination local binary feature and color histogram Shift target tracking algorisms, are introduced local binary feature (LBP), and make which be combined with color characteristic in the present invention so that On the basis of using color of object feature, further with the texture information such as edge and angle point of target so as in different background The robustness of target following can be guaranteed under interference cases, the robustness and adaptability of algorithm is improve.Additionally, in tracking process In matrix decomposition is carried out to target area, estimated using the square information of target area track during target yardstick and side To so that the method for tracking target that the present invention is provided can be continually changing efficiently against target scale during tracking and direction Problem, it is described below:
1) object module and candidate target description:The texture of object module and candidate target model by selected target region The joint histogram of feature (improved LBP operators) and color characteristic composition describing, with mesh in classical Mean Shift algorithms The description of mark model is compared, and overcomes the single shortcoming of object module:When illumination in scene is tracked changes, by target The tracking failure that the distribution of color in region changes and causes.And the object module described by joint histogram in the present invention, For illumination variation has stronger robustness, and when background is similar to color of object, there is stronger discriminating energy to target Power;Additionally, the arithmetic speed of algorithm is also further improved.
2) similarity measurement:Bhattacharyya coefficients represent two vectors and between angle cosine value, its value gets over Greatly, represent object module more similar to target candidate model, it calculates simple, in the target following based on Mean Shift algorithms Used in it is the most extensive.
3) target scale direction estimation:On the basis of object module is described using joint histogram, during tracking, Our square information based on union feature weight map using selection area, effectively estimate yardstick and the direction of tracking target Change, the tracking failure caused due to target deformation during overcoming tracking.Therefore, the combination local two that the present invention is provided Value tag and the adaptive Mean Shift target tracking algorisms of dimension of color histogram, can preferably adapt to illumination Difficult point in the target following such as change and ambient interferences, while carrying for the limitation of target deformation in improving traditional algorithm High track algorithm reliability and robustness based on MeanShift.
To make the object, technical solutions and advantages of the present invention clearer, further is made to embodiment of the present invention below Ground is described in detail.
Embodiment 1
A kind of dimension adaptive Mean Shift target followings of combination local binary feature and color histogram Method, its corresponding schematic diagram of tracking framework is as shown in figure 1, tracking can be divided into three steps:Object module is generated, target scale Direction estimation and similarity measurement.
(1) object module is generated:
In the tracking that the present invention is provided, the connection that object module is made up of with color characteristic the local binary feature of image Rectangular histogram is closed describing, that is, utilizes color and textural characteristics in the mask formed by local binary patterns to describe target, structure Build the object module of joint texture-color characteristic.
(2) similarity measurement:
The similarity between object module and target candidate model is weighed using Bhattacharyya coefficients. Bhattacharyya coefficients represent two vectors and between angle cosine value, its value is bigger, represents object module and waits with target Modeling type is more similar, and which calculates simple, the most extensive used in the target following based on Mean Shift algorithms.Calculate first The Bhattacharyya coefficients of above-mentioned object module and target candidate model, and specify certain measurement criterion so as in the criterion Lower similarity highest.
(3) target scale direction estimation:
During tracking, Mean shift iteration is carried out first to target area so as to converge to the sky of candidate target Between at position, the object candidate area weight map of the joint texture-color characteristic to generating in (1) carries out matrix decomposition, utilizes Matrix analyses are calculating yardstick and the direction of object candidate area.
In sum, the introducing of local binary feature (improved LBP) causes the description of object module to be no longer limited to list One color characteristic, meanwhile, on this basis, matrix decomposition is carried out to the weight map of target area, effectively estimated using square information is gone Meter target scale and direction, therefore, the image sequence method for tracking target that the present invention is provided is for illumination condition and target deformation Under image sequence target following all there is higher reliability and robustness;
Embodiment 2
The scheme in embodiment 1 is introduced in detail with reference to Fig. 1, design principle, it is described below:
A kind of dimension adaptive Mean Shift target followings of combination local binary feature and color histogram Method, which adds the corresponding schematic diagram of tracking framework as shown in figure 1, object module generation, target scale direction estimation and similarity Tolerance.Below the specific embodiment of this three part is described in detail respectively.
(1) object module generating portion:
The description of object module in the tracking that the present invention is provided, by local binary feature (LBP) and color characteristic group Into joint histogram composition.Local binary feature with regard to how to extract target area describes in detail below.
Local binary patterns (Local Binary Pattern, LBP) are one kind for describing image local textural characteristics Operator, its extraction is characterized in that the Local textural feature of image.Original LBP operator definitions be in 3 × 3 window, with Window center pixel is threshold value, and the gray value of 8 adjacent pixels is compared with which, if surrounding pixel values are more than middle imago Element value, then the position of the pixel is marked as 1, is otherwise 0.Therefore, 8 points in 3 × 3 fields can produce 8bit without symbol Count, calculates its corresponding decimal number, that is, obtain the LBP values of the window, and believed come the texture for reflecting the region with this value Breath.
Its basic mathematic(al) representation is:
Wherein, (xc,yc) window center point transverse and longitudinal coordinate, gcThe pixel value of correspondence window center point is represented, P is represented (xc,yc) pixel around window center point, gpFor the pixel value in picture centre surrounding neighbors, R represents the model of neighborhood Enclose.Function s (x) is defined as follows:
The LBP operators of said extracted obtain a LBP coding in each pixel, therefore, which is extracted to piece image After original LBP operators, that is, binary feature is converted into, and the original LBP features for obtaining are still a width picture.From upper The analysis in face is, it can be seen that original LBP features are closely related with positional information.Therefore, LBP is extracted to two width pictures directly special Levy, and carry out discriminant analysiss, larger error can be produced due to position difference.Therefore, above-mentioned original LBP features only have ash Degree scale invariability, not with rotational invariance, can not be directly used in discriminant analysiss.With grey scale invariance and rotation The LBP operators for turning invariance can pass through following model acquisition:
Wherein, riv2 represents invariable rotary equivalent formulations, U (LBPP,R) defining for invariable rotary pattern LBP operator, its Value≤2, expression light from starting point 0, calculate it is adjacent 2 points with the difference of function s (x) of central point pixel value, travel through P successively Individual pixel:
Wherein, gp-1Represent the pixel value of pixel p-1 in neighborhood, g0Represent the pixel value of starting point in neighborhood;In image Flat site in, the fluctuation very little of pixel value.Therefore the limitation of LBP operators is, it is impossible to effectively flat in description image Region.In order that LBP operators can effectively overcome this shortcoming, the threshold value in LBP operators is improved.With S (gP-gc+ a) generation For S (gP-gc).Wherein, a is to make up the little threshold value for setting of pixel fluctuation in flat site;And | a | is bigger, pixel fluctuation Permissible value is bigger.The present invention adopts improved threshold method, and utilizesOperator is extracting the Local textural feature of target.
After the binary feature for extracting image, below with regard to how effectively joint objective local binary feature (LBP) and face Color characteristic describes in detail:
Object module q based on solid color featureuWith target candidate model puRespectively:
Wherein, c is normaliztion constant, the center of y candidate target regions, quAnd puY () is illustrated respectively in target area And in candidate target region probability distribution rectangular histogram feature u probability;MeetU=1,2...m is represented Any one color index, b (xi) represent xiThe corresponding color index value of place's pixel;{xi}I=1,2..., nRepresent target area pixel The coordinate position of point, y represent the center of candidate target model, n and nhPicture in target area and candidate region is represented respectively The number of vegetarian refreshments, k (x) are Epanechinkov kernel functions, and h represents kernel function window width, and its effect is according to different pixels The distance of point distance center point, gives each pixel different weights, and the nearer pixel of distance center, weights are bigger.
The joint histogram by obtained from the color characteristic of the LBP feature direct union images of said extracted can not be effective Strengthen the tracking performance of mean shift algorithms, especially when target and background color similarity, constituted using this texture-color Joint histogram can not effective district partial objectives for and background.It would therefore be desirable to set up a kind of significantly more efficient integrated processes.
It is above-mentioned improvedThere are 9 uniform texture patterns, each LBP texture pattern can be considered as a micro- stricture of vagina Reason primitive,In topography's block that operator is detected, feature is included a little, flat site, edge, the starting point of line segment and Terminal.In object representation, above-mentioned microtexture primitive such as angle point, edge, line segment etc. is referred to as main target pattern, represents Most of feature of target, and point, plane domain are referred to as secondary target pattern, are the secondary textures of target.So, we The main target pattern of target is extracted by equation below:
In operator, the secondary target pattern of the correspondence of labelling 0,1,7,8, labelling 9 do not correspond to target pattern.Cause This, main target pattern is marked with:2~6.In general, compared with secondary LBP patterns, the main LBP features of target are more It is important, target more effectively accurately can be described.Therefore, the main LBP patterns of target are extracted by formula (7), then joint image Color feature target, be built into the joint histogram of 8 × 8 × 8 × 5 four-dimensional joint texture-color.Thus combine straight The object module of side's figure description, for illumination variation has stronger robustness, and when background is similar to color of object, to mesh Mark is with stronger distinguishing ability;
(2) similarity measurement part:
Object module adopts Bhattacharyya coefficients ρ (y) to weigh with the similarity of candidate target model, i.e.,
WhereinBhattacharyya coefficients ρ (y) defines tracking target and candidate's mesh Target similarity, additionally, defining metric function d (y), which represents the distance between tracking target and candidate target model:
Bhattacharyya is bigger, and object module is more similar to candidate target, therefore finds candidate target optimal location, Bhattacharyya coefficients need to be maximized, that is, minimizes d (y).To ρ [p (y) q] in pu(y0) place carries out Taylor series expansion, High-order term is removed, only retains single order expansion, the linear approximation formula for obtaining ρ [p (y) q] is as follows:
y0Represent the center of target candidate model in previous frame, pu(yo) represent previous frame target candidate model;Will Object module is substituted into candidate target model and can be obtained:
Wherein,
In formula (11), Section 1 is unrelated with y, and the Density Estimator at Section 2 denotation coordination y, wherein each pixel xiWeight w (xi) represent.So the problem for finding best candidate target translates into searching probability density function local extremum The problem of position, can be completed by the method for Mean shift iteration.Therefore, above formula (11) is maximized, evenObtain the iteration form of Mean shift:
Wherein, g (x)=- k'(x), with previous frame target location y0For initial value, the y in above formula is iterated to calculate, until receiving Hold back or reach the maximum iteration time of setting.
(3) target scale direction estimation part:
In classical Mean shift target tracking algorisms, the width and height for tracking target window be it is fixed, and It is always maintained at during tracking constant.When tracked target scale and direction change, fixed tracking window is just The deformation of target can not be well adapted to, causes the tracking performance of algorithm to gradually reduce, or even tracking failure.
As the scale size of target area is closely related with the weight map in direction and goal region, therefore, present invention profit During being estimated to track with the square information of candidate target region weight map, the dimension change of target, carrys out adaptive targets Deformation.In previous frame, optimal objective region is searched out using Mean shift iterative algorithms, as current tracking result, Then the zeroth order square M in the region is calculated using following formula00
Generally, w (xi) represent each pixel xiThe weight at place, n are the number of pixel in target area;We are by zero Rank square regards target area size as, but, when the weight of target reduces, the error of zeroth order square increases therewith;And Bhattacharyya coefficients react the similarity of object module and target candidate model, its value between 1~0, therefore, we The error caused by zeroth order square is corrected using Bhattacharyya coefficients, following formula is defined:
A=c (ρ) M00 (15)
C (ρ) is the monotonically increasing function related to Bhattacharyya coefficient ρ, and its value is between 0~1:
Wherein, σ is adjustable parameter.When ρ (0~1) reduces, c (ρ) (0~1) also reduces;I.e. with object module and time Model similarity is selected to reduce, M00Bigger than the area in real goal region, i.e., error is bigger;Therefore, less c (ρ) can be very Good correction M00The error for causing.
The center of next frame object candidate area, yardstick and direction, can be to the first order and second order moments of weight map Carry out matrix analyses to obtain.First moment M is calculated to weight map10、M01With second moment M20、M02、M11Difference is as follows:
Wherein, (xi,1,xi,2) for pixel xiCoordinate, and the center y of next frame candidate target region can be by upper The ratio for stating first moment and zeroth order square is tried to achieve:
Wherein, the center of y next frames candidate target region,Represent the coordinate of center y;Equally, second order The square information of square can be used to describe the shape of target area and direction, calculate ratio and the center of second moment and zeroth order square CoordinateThe difference of two squares, respectively μ20μ11μ02
To analyze scale size and the direction of target area, we are μ2002, μ11Write covariance matrix Cov, and to association Variance matrix carries out singular value decomposition:
Wherein,
U, S carry out two matrixes after singular value decomposition for covariance matrix, wherein, (u11,u21)T(u12,u22)TPoint The direction of two axles of target in object candidate area is not represented, the direction of target can be obtained by the angle between major axis and trunnion axis Go out.Additionally, λ12For the eigenvalue of covariance matrix Cov, its ratio is identical with the ratio of target area major and minor axis, i.e. λ12 =a/b.Introduce scale factor k so that a=k λ1, b=k λ2, then the area of target area be:π ab=π (k λ1)(kλ2)=A, So, the major and minor axis (a, b) of target area are respectively:
Thus, the yardstick of target and direction during tracking just are estimated, enables the tracking of the present invention adaptive The size of adjustment tracking outlet and direction.
In sum, the introducing of improved local binary feature (LBP) causes the description of object module to be no longer limited to list One color characteristic, it is similar to background color for illumination variation and color of object in the case of tracking with higher robust Property.Meanwhile, on this basis, its zeroth order square, first moment and second moment is calculated to the weight map of target area, and by matrix point Analysis method effectively estimates target scale and direction.Therefore, the image sequence method for tracking target that the present invention is provided is for illumination bar Image sequence target following under part and target deformation all has higher reliability and robustness;
Embodiment 3
Feasibility checking is carried out to the scheme in embodiment 1 and 2 with reference to specific accompanying drawing, it is described below:
The tracking for providing is implemented under 3 groups of illumination variations and background and color of object similar situation using the present invention Video is tracked, and is compared with the tracking result of SOAMST algorithms under the same conditions, the part tracking result for obtaining Respectively as shown in figure (2), (3), (4).
In the video sequence shown in figure (2), the region of wild goose and its surrounding is chosen to be tracking target, target in video Identification is very low, and the dimension of wild goose constantly changes during tracking.Fig. 2 (a), (b) represent this respectively Part tracking result obtained by the track algorithm and SOAMST algorithms of bright offer, and the mesh that two kinds of algorithms are selected at initial frame Mark region is identical.Knowable to the tracking result of Fig. 2, the track algorithm that the present invention is provided can be positioned to target well, Tracking accuracy is higher, achieves tracking effect well.And SOAMST algorithms start to shift in 31 frame, 33 frames with Afterwards, there is larger skew with tracking box center in target's center, cause follow-up tracking failure.
In the video sequence shown in figure (3), the region of automobile and its surrounding is chosen to be tracking target, this video sequence In, background color is more complicated, and color of object is similar to background color.Fig. 3 (a), (b) represent the tracking of present invention offer respectively Part tracking result obtained by algorithm and SOAMST algorithms, and the target area that two kinds of algorithms are selected at initial frame is identical. The tracking result of contrast Fig. 3 understands that the track algorithm that the present invention is provided can lock tracked target well, with higher Tracking precision, and during whole tracking, there is not tracking failure phenomenon.
In the video sequence shown in figure (4), the region of automobile and its surrounding is chosen to be tracking target, this video sequence In, background color is more complicated, and with obvious illumination variation.Fig. 4 (a), (b) represent the track algorithm of present invention offer respectively And part tracking result obtained by SOAMST algorithms, and the target area that two kinds of algorithms are selected at initial frame is identical.Contrast The tracking result of Fig. 4 understands, under the tracking situation that background is complicated and illumination variation is strong, the track algorithm energy that the present invention is provided Enough with accurately tracking target, tracking box is coincide substantially with target, not comprising unnecessary background color.
Thus, the present invention is provided combination local binary feature and the adaptive Mean of dimension of color histogram Shift method for tracking target, for background complexity, illumination variation, target is similar to background color and dimension changes scene Under image sequence target following there is higher robustness.
It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferred embodiment, the embodiments of the present invention Sequence number is for illustration only, does not represent the quality of embodiment.
The foregoing is only presently preferred embodiments of the present invention, not to limit the present invention, all spirit in the present invention and Within principle, any modification, equivalent substitution and improvements made etc. should be included within the scope of the present invention.

Claims (5)

1. it is a kind of to combine LBP feature adaptive M ean Shift method for tracking target, it is characterized in that, step is as follows:
(1) object module is generated:
The joint histogram that object module is made up of with color characteristic the local binary feature of image is utilized by local describing The color in mask that binary pattern is formed and textural characteristics build the target mould of joint texture-color characteristic describing target Type;
(2) similarity measurement:
The similarity between object module and target candidate model is weighed using Bhattacharyya coefficients, Bhattacharyya coefficients represent two vectors and between angle cosine value, its value is bigger, represents object module and waits with target Modeling type is more similar, calculates the Bhattacharyya coefficients of above-mentioned object module and target candidate model first, and specifies certain Measurement criterion so as to the similarity highest under the criterion;
(3) target scale direction estimation:
During tracking, Mean shift iteration is carried out first to target area so as to converge to the space bit of candidate target Place is put, the object candidate area weight map of the joint texture-color characteristic to generating in (1) carries out matrix decomposition, using matrix Yardstick and the direction for analyzing to calculate object candidate area.
2. LBP feature adaptive M ean Shift method for tracking target is combined as claimed in claim 1, it is characterized in that having The local binary patterns LBP operators of grey scale invariance and rotational invariance are obtained by following model:
Wherein, represent gcThe pixel value of correspondence window center point, P represent (xc,yc) pixel around window center point, gpFor in Pixel value in heart vertex neighborhood, R represent the scope of neighborhood, and riv2 represents invariable rotary equivalent formulations, U (LBPP,R) for rotation Constant pattern LBP operator is defined, its value≤2, and expression is lighted from starting point 0, calculates at adjacent 2 points with central point pixel value The difference of function s (x), travels through P pixel successively:
Wherein, gP-1Represent the pixel value of pixel P-1 in neighborhood, g0Represent the pixel value of starting point in neighborhood;With S (gP-gc+ A) S (g are replacedP-gc), a is to make up the little threshold value for setting of pixel fluctuation in flat site;Also, | a | is bigger, pixel fluctuation Permissible value is bigger.
3. LBP feature adaptive M ean Shift method for tracking target is combined as claimed in claim 1, be it is characterized in that, effectively Local binary feature LBP and the color characteristic of joint objective is comprised the following steps that:
There are 9 uniform texture patterns, each LBP texture pattern can be considered as a microtexture primitive,Calculate In topography's block that son is detected, feature is included a little, flat site, edge, the starting point and terminal of line segment, in object representation In, above-mentioned microtexture primitive includes angle point, edge, line segment, and referred to as main target pattern represents the major part of target Feature, and point, plane domain are referred to as secondary target pattern, are the secondary textures of target;Mesh is extracted by equation below Target major part target pattern:
In operator, the secondary target pattern of the correspondence of labelling 0,1,7,8, labelling 9 do not correspond to target pattern.Therefore, it is main The target pattern wanted is marked with:2~6, the main LBP patterns of target are extracted by formula (7), then the color characteristic of joint image Description target, is built into the joint histogram of 8 × 8 × 8 × 5 four-dimensional joint texture-color.
4. LBP feature adaptive M ean Shift method for tracking target is combined as claimed in claim 1, be it is characterized in that, target Model adopts Bhattacharyya coefficients ρ (y) to weigh with the similarity of candidate target model, i.e.,
Wherein, y represents candidate target region center, and u=1,2...m represent any one color index, Object module and candidate target model are represented respectively;quAnd puY () is illustrated respectively in target area and candidate's mesh The probability of feature u in mark areal probability distribution rectangular histogram;Bhattacharyya coefficients ρ (y) defines tracking target and candidate's mesh Target similarity, additionally, defining metric function d (y), which represents the distance between tracking target and candidate target model:
Bhattacharyya is bigger, and object module is more similar to candidate target, to ρ [p (y) q] in pu(y0) place carries out Taylor's level Number launches, and removes high-order term, only retains single order expansion, and the linear approximation formula for obtaining ρ [p (y) q] is as follows:
y0Represent the center of target candidate model in previous frame, pu(yo) represent previous frame target candidate model;By target Model is substituted into candidate target model and can be obtained:
Wherein,
In formula (11), Section 1 is unrelated with y, and Section 2 represents the Density Estimator at candidate target region central point y, wherein Each pixel xiWeight w (xi) represent.So the problem for finding best candidate target translates into searching probability density letter The problem of number local extremum positions, and above formula (11) is maximized completing by the method for Mean shift iteration, evenObtain the iteration form of Mean shift:
Wherein, g (x)=- k'(x), with previous frame target location y0For initial value, iterate to calculate the y in above formula, until convergence or Person reaches the maximum iteration time of setting.
5. LBP feature adaptive M ean Shift method for tracking target is combined as claimed in claim 1, be it is characterized in that, target Dimension estimate comprise the concrete steps that, estimated using the square information of candidate target region weight map track during target chi Degree direction change, carrys out the deformation of adaptive targets, in previous frame, searches out optimal objective using Mean shift iterative algorithms Region, as current tracking result, then calculates the zeroth order square M in the region using following formula00
w(xi) represent each pixel xiThe weight at place, n are the number of pixel in target area;Using Bhattacharyya Coefficient defines following formula correcting the error caused by zeroth order square:
A=c (ρ) M00 (15)
C (ρ) is the monotonically increasing function related to Bhattacharyya coefficient ρ, and its value is between 0~1:
Wherein, σ is adjustable parameter.When ρ (0~1) reduces, c (ρ) (0~1) also reduces;I.e. with object module and candidate's mould Type similarity reduces, M00Bigger than the area in real goal region, i.e., error is bigger;
The center of next frame object candidate area, yardstick and direction, are carried out by the first order and second order moments to weight map Matrix analyses are obtained, and calculate first moment M to weight map10、M01With second moment M20、M02、M11Difference is as follows:
Wherein, (xi,1,xi,2) for the coordinate of pixel i, and the center of next frame candidate target region is by above-mentioned first moment Try to achieve with the ratio of zeroth order square:
Wherein, centers of the y for next frame candidate target region,Represent the coordinate of center y;Equally, second moment Square information can be used to describe the shape of target area and direction, the ratio for calculating second moment and zeroth order square is sat with center MarkThe difference of two squares, respectively μ20μ11μ02
To analyze scale size and the direction of target area, μ2002, μ11Write covariance matrix Cov, and to covariance square Battle array carries out singular value decomposition:
Wherein,
U, S carry out two matrixes after singular value decomposition for covariance matrix, wherein, (u11,u21)T(u12,u22)TRepresent respectively The direction of two axles of target in object candidate area, the direction of target can be drawn by the angle between major axis and trunnion axis, additionally, λ12For the eigenvalue of covariance matrix Cov, its ratio is identical with the ratio of target area major and minor axis, i.e. λ12=a/b, draws Enter scale factor k so that a=k λ1, b=k λ2, then the area of target area be:π ab=π (k λ1)(kλ2)=A, so, target The major and minor axis (a, b) in region are respectively:
Thus, the yardstick of target and direction during tracking just are estimated.
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