CN103714148B - SAR image search method based on sparse coding classification - Google Patents

SAR image search method based on sparse coding classification Download PDF

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CN103714148B
CN103714148B CN201310733522.8A CN201310733522A CN103714148B CN 103714148 B CN103714148 B CN 103714148B CN 201310733522 A CN201310733522 A CN 201310733522A CN 103714148 B CN103714148 B CN 103714148B
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sparse
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CN103714148A (en
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焦李成
马文萍
高晓莹
尚荣华
杨淑媛
马晶晶
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Xidian University
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    • G06F16/50Information retrieval; Database structures therefor; File system structures therefor of still image data
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Abstract

The invention provides an SAR image search method based on sparse coding classification. The SAR image search method aims at the defects of an existing image search system and method. Through extraction of characteristics and construction of an over-complete dictionary, solution is carried out through sparse representation based on a dual Memetic algorithm, a sparse representation classifier is trained, the classification process with supervision can be achieved in the classification process, the sparse solution with global optimum can be solved fast, and then search results are output from high to low according to similarity. When the problem of image classification is solved, the method achieves the good improvement effect on classification accuracy, search content similarity, calculating complexity and result robustness.

Description

Based on the SAR image search method that sparse coding is classified
Technical field
The invention belongs to SAR image process field, is related to a kind of SAR image search method based on sparse coding, can be with Accurately classified and realized retrieval to SAR image, significantly reduced shadow of the coherent speckle noise to SAR image classification results Ring.
Background technology
Synthetic aperture radar-SyntheticApertureRadar, is a kind of effective means from earth observation from space, It has been widely applied to the aspects such as military surveillance, landform observation, urban planning.With carrying for SAR imaging techniques in recent years Height, the quantity of SAR image is presented explosive growth, many for SAR image data volume, the characteristics of self-noise is big, how from Image required for efficiently and accurately retrieving in the SAR image storehouse of magnanimity has become problem demanding prompt solution.
With the development of information technology, the search method of image is transformed into from initial text based retrieval method Content-based retrieval method, the method can directly be analyzed to image, feature extraction, and similarity analysis simultaneously realize inspection Rope.At present, main image indexing system includes:The QBIC systems of IBM exploitations, Virage systems, stanford university research The SIMPLIcity systems of exploitation, the still image searching system of the Internet platforms of Tsing-Hua University's research and Chinese Academy of Sciences's exploitation Mires image retrieval prototype systems.Data base used by these systems contains natural image, biometric image, multispectral figure As etc., but for the particularity of SAR image, these systems are not simultaneously applied to.
Image classification is to realize the key link of CBIR.At present, conventional image classification method master It is divided into two classes:There are the method and unsupervised method of supervision.The sorting technique for having supervision includes:Arest neighbors and k- neighbours, shellfish Leaf this grader, support vector machine and neutral net.These methods can fast and accurately realize the classification of image, but be because The foundation and study of model are needed in processing procedure, the time complexity of method is higher;Unsupervised image classification method has Cluster analyses and fuzzy cluster analysis.Both approaches realize that process is more quick, but the accuracy of classification is but than relatively low. Therefore, the classification of SAR image how is fast and accurately realized, is the major issue for solving SAR image retrieval.
The content of the invention
Present invention aims to the shortcoming of above-mentioned existing system and method, it is proposed that one kind is based on sparse coding That what is classified has supervision SAR image search method, and it can quickly solve the sparse solution of global optimum.The method can not only The computation complexity that SAR image is processed is reduced, and coherent speckle noise can be effectively reduced and SAR image retrieval result is caused Impact.
The technical scheme is that, based on the SAR image search method that sparse coding is classified, it is characterized in that:At least wrap Include following steps:
Step 101:Start based on the SAR image retrieval of sparse coding classification;
Step 102:Training image is chosen in SAR image storehouse, these images are read in, each image selected in this patent Size is 256 × 256, and the method filtered using exquisite Lee carries out pretreatment to it, reduces coherent speckle noise to image classification As a result the impact for causing, the window size of wave filter is set as 7 × 7;
Step 103:Feature extraction is carried out using the method for gray level co-occurrence matrixes to pretreated training image, is chosen 0 °, 45 °, 90 °, the energy, entropy, contrast, local similarity, related each five features on 135 ° of directions, each width training figure As correspondence obtains the column vector that dimension is 20;
If pij(d, θ) is represented in given space length d and direction θ, with gray scale i as initial point, the probability of gray level j is occurred (i=1,2 ... G;J=1,2 ... G), G is the maximum of gray level in institute's image under consideration region, then gray level co-occurrence matrixes are one The square formation of individual G × G, note
Formula(1)
Formula(2)
The value of θ is set as 0 °, 45 °, 90 °, 135 °, in order to obtain image textural characteristics in all directions, to upper State 4 directions and construct the corresponding characteristic vector of gray level co-occurrence matrixes extraction respectively;From feature include following five kinds of features:
A) energy, also known as angular second moment:
Formula(3)
It is the tolerance of gradation of image distributing homogeneity or flatness.When Elemental redistribution is relatively concentrated in gray level co-occurrence matrixes When near leading diagonal, gradation of image distribution uniform in regional area is illustrated, image is presented thinner texture, angular second moment Value is larger;
B) entropy:
Formula(4)
Entropy is the tolerance that image has quantity of information, is the characteristic parameter for measuring grey level distribution randomness, is characterized The complexity of texture in image;The gray scale of image is more uniform, and entropy is less, and the texture of image is more complicated, and entropy is then bigger;Separately On the one hand, entropy can also measure the randomness of image texture, and entropy is bigger, and gray scale distribution randomness is big in representative image;
C) contrast, also known as the moment of inertia:
Formula(5)
Local gray level change total amount in its phenogram picture, reflects the definition of image and the rill depth of texture;Stricture of vagina The rill depth of reason, contrast is big, and effect is clear;Conversely, contrast is little, then rill is shallow, and effect is obscured;If that is, partially Higher value, i.e. gradation of image value changes are have from cornerwise unit quickly, then contrast value has larger value;
D) local similarity:
Formula(6)
Local similar performance portrays the textural characteristics of regional area, is to discriminate between the important measure of different target;
E) it is related
Formula(7)
Wherein,
Therefore, after gray level co-occurrence matrixes have been calculated, each image can obtain 20 features, i.e. dimensionality reduction to a dimension It is 20 column vector;
Step 104:Complete dictionary was constituted using the characteristic vector obtained in step 103, sparse grader was trained;
Step 105:Whole SAR picture libraries are classified using the sparse grader for training;
Step 106:The category and corresponding sparse solution of each image in storage SAR image storehouse;
Step 107:Import test SAR image, it is desirable to which its size is equal in magnitude with the SAR image in image library, according to step Method in rapid 102 is filtered process to test image;
Step 108:Method according to the gray level co-occurrence matrixes in step 103 carries out feature extraction to test image, obtains Corresponding 20 features;
Step 109:Judge that test image whether in the SAR image storehouse that step 106 is obtained, is if so, then directly walked Rapid 110, otherwise into step 111;
Step 110:Directly extract and test image identical SAR image in the SAR image storehouse for having category;
Step 111:Test image is classified using the sparse grader for training before;
Step 112:The class label and its corresponding sparse solution of storage test image;
Step 113:The image of identical category is proposed in the SAR image storehouse for having category according to the classification of test image, is entered Row image similarity is matched;Test image and the Euclidean distance of the sparse solution of generic image are calculated first, are then found sparse The position that greatest coefficient is located in solution, calculates the difference of two positions, and the module of similarity is set as Euclidean distance and position The inverse of the absolute value of the product of difference, value is bigger, represents Similarity value higher.Similarity expression formula is:
Formula(8)
WhereinFor Euclidean distance expression formula, xiRepresent i-th in the corresponding sparse solution of test image Sparse coefficient on individual position, mxFor the position that greatest coefficient is located;uiRepresent the dilute of the training image generic with test sample Discongest the sparse coefficient on i-th position, nuFor the position that its greatest coefficient is located.
Step 114:By the Similarity value for obtaining, arranged according to order from big to small, returned retrieval result;
Step 115:Terminate the SAR image search method of sparse coding classification.
Described step 104, comprises the steps:
Step 201:Start to build complete dictionary and train sparse grader;
Step 202:Constructed complete dictionary:The corresponding characteristic vector of training image is arranged according to classification, it is identical The feature column vector of classification is discharged successively together, constructs the excessively complete dictionary A=[χ required for rarefaction representation12,... χn], χiRepresent one type training sample, χi=[α12,...αk], the total classification number of training sample is n;
Step 203:Obtain the excessively complete dictionary in new local:By each the training sample in sample to be sorted and excessively complete dictionary This subtraction calculations residual values, set threshold value T, and residual values are proposed more than the training sample corresponding to threshold value, and composition is new The excessively complete dictionary A in local1=[χ12,...χk];
Step 204:Using based on the dilute optimization method y=Ax of dual Local Search Memetic Algorithm for Solving, sparse solution is obtained X, y is original test image in optimization method, and A is the excessively complete dictionary of training image composition, and x is the corresponding sparse solutions of y;
Step 205:Design classification function δi,(δi∈Rm×n), coefficients all kinds of in sparse solution x are proposed respectively, construct new Sparse solution δi(x).The coefficient value for there was only a class in new sparse solution is not zero, and the value of remainder is zero;Therefore, press Test sample is reconstructed according to below equation
Formula(9)
The process simplification of final image classification is the following problem of solution:
Formula(10)
Wherein, | | | |1Represent L1- norm, | | | |2Represent L2- norm, A is the excessively complete dictionary of training image composition.
Calculate original sample y to be sorted and reconstructed sampleTwo poor norms, the classification that the minima for obtaining is located is The classification that test sample belongs to;
Step 206:Terminate the process of the sparse grader of training.
Described step 204, comprises the steps:
Step 301:Start with based on the dilute optimization method of Memetic Algorithm for Solving of dual Local Search, obtain sparse Solution;
Step 302:The selection of individuality and coding, by the excessively complete dictionary A in local1In training sample position as individuality Encoded, coded system adopts decimal coded mode, if including five sample positions in each individuality;
Step 303:The corresponding training sample of five coding sites is proposed into the new dictionary A of composition2, calculated using match tracing Method-MP, solving-optimizing problem y=Ax obtains the sparse coefficient under the dictionary;
Step 304:The selection of fitness function:By sample y to be sorted and reconstructed sampleDifference two norms be set to adapt to Degree function, the value of two norms is less to represent that fitness is higher;
Step 305:Judge whether fitness value meets first end condition-residual values less than setting value or reach most Big iterationses, if meeting, jump directly to step 310, otherwise continue executing with step 306;
Step 306:Select, sample is selected according to the height of fitness value, retain excellent individual, i.e. fitness compared with High individuality;
Step 307:Intersect, the mode of intersection is handed over the part behind cross point to randomly generate a cross point Change, adjacent individuality intersects two-by-two;
Step 308:Variation, the mode of variation enters row variation to randomly select single-point.
Step 309:First stage Local Search, when obtaining preferably individual after each iteration, in local dictionary A1In Using the neighborhood position of left and right n of each position as Local Search candidate constituency, again according to the height of fitness in candidate regions It is low to be selected, update existing more excellent individuality;After first stage Local Search is completed, global search process steps are returned to 304, individual fitness value is calculated, carry out the judgement of next execute instruction;
Step 310:The Local Search of second stage, after all iterative process are completed, according to the search in step 309 Method, in whole excessively complete dictionary A a Local Search is carried out again;
Step 311:Judge whether to meet end condition-residual values less than setting value or reach maximum iteration time, if full Foot carries out step 312, otherwise return to step 310;
Step 312:The final global optimum for meeting condition of output is individual, and the position in individuality is required for us The position that sparse coefficient is located;
Step 313:Terminate the process using the Memetic Algorithm for Solving sparse solutions based on dual Local Search.
There is advantages below compared with prior art in the present invention:
1. this method is first classified to SAR image, then retrieves similar image according to category, which reduces coherent spot The impact that noise is caused to SAR image retrieval result.
2. in categorizing process, by encoding position of the training sample in excessively complete dictionary, we can build one New dictionary A2, so as to represent original test sample using less sparse coefficient, operand is efficiently reduced, be conducive to Quickly realize the classification of image.
3. in categorizing process, this paper presents the method for dual Local Search.Selecting every time, intersecting, after variation, Carry out first stage Local Search.According to preferably individuality in dictionary A1Middle selection candidate region, candidate region be set as this five The neighborhood of left and right n of individual position, the method can simply, efficiently obtain optimal solution.After iterative process is completed, is carried out The Local Search of two-stage, now we candidate spatial is amplified in entirely excessively complete dictionary A, which ensures that optimal solution It is of overall importance.Also, compared with other evolution algorithms, the method solution procedure is more quick.
4. in similarity mode, the absolute value of Euclidean distance and position difference product is chosen as module, with reference to The detailed information of image, with principal component information, makes retrieval result more accurate.
The specific implementation step of the present invention is further described with reference to flow process Fig. 1 and other accompanying drawings.
Description of the drawings
Fig. 1 is SAR image retrieval flow figure of the present invention based on sparse classification;
Fig. 2 is the flow chart that the present invention realizes image classification;
Fig. 3 (a) is rarefaction representation process, (b) is the example of sparse solution x;
Fig. 4 be set forth herein the Memetic algorithms based on dual Local Search flow chart;
Fig. 5 is the process diagram of the mode of individual UVR exposure and the new dictionary of generation when initial population is produced;
Fig. 6 is the method figure that Local Search candidate region is chosen after more excellent solution is calculated;
Fig. 7 is that 5 class SAR images needed for classifying in this paper experimentations are followed successively by city, farmland, bridge, mountains and rivers, water Domain;
Fig. 8 be use set forth herein method and use orthogonal matching algorithm, method of least square, base tracing algorithm, step move it is orthogonal Matching pursuit algorithm, the comparing result of the classification accuracy that Memetic algorithms are obtained;
Fig. 9 is the retrieval result of every class SAR image.
Specific embodiment
As shown in Figure 1.Based on the SAR image search method that sparse coding is classified, at least including process step:
Step 101:Start based on the SAR image search method of sparse coding classification;
Step 102:Training image is chosen in SAR image storehouse, these images are read in, each image selected in this patent Size is 256 × 256, and the method filtered using exquisite Lee carries out pretreatment to it, reduces coherent speckle noise to image classification As a result the impact for causing, the window size of wave filter is set as 7 × 7;
Step 103:Feature extraction, set direction are carried out using the method for gray level co-occurrence matrixes to pretreated training image The value of θ is 0 °, 45 °, 90 °, 135 °, i.e. east-west, northeast-southwest, southern-northern, direction of the southeast-northwest 4;Each side It is respectively energy, entropy, contrast, local similarity and correlation to 5 features are chosen.Therefore, each image can obtain 20 Feature, i.e. dimensionality reduction are to the column vector that dimension is 20.
In an embodiment of the present invention, classification process is carried out using 5 class SAR images, is respectively cities and towns, farmland, bridge, mountain River and waters, are 200 per class amount of images, and image size is 256 × 256, as shown in Figure 7;
Step 104:Using in step 103 to characteristic vector constituted complete dictionary, solving-optimizing equation y=Ax, instruction The sparse grader of white silk.Y is original test image in optimization method, and A is the excessively complete dictionary of training image composition, and x is that y is corresponding Sparse solution;
Step 105:Whole SAR picture libraries are classified using the sparse grader for training;
Step 106:The category and corresponding sparse solution of each image in storage SAR image storehouse;
Step 107:Import test SAR image, it is desirable to which its size is equal in magnitude with the SAR image in image library, according to step Method in rapid 102 is filtered process to test image.
In an embodiment of the present invention, it is respectively per the number of class testing sample, 360,433,167,400,400;
Step 108:Method according to the gray level co-occurrence matrixes in step 103 carries out feature extraction to test image, obtains Corresponding 20 features;
Step 109:Judge that test image whether in the SAR image storehouse that step 106 is obtained, is if so, then directly walked Rapid 110, otherwise into step 111;
Step 110:Directly extract and test image identical SAR image in the SAR image storehouse for having category;
Step 111:Test image is classified using the sparse grader for training before;
Step 112:The class label and its corresponding sparse solution of storage test image;
Step 113:The image of identical category is proposed in the SAR image storehouse for having category according to the classification of test image, is entered Row image similarity is matched.Test image and the Euclidean distance of the sparse solution of generic image are calculated first, are then found sparse The position that greatest coefficient is located in solution, calculates the difference of two positions, and the module of similarity is set as Euclidean distance and position The inverse of the absolute value of the product of difference, value is bigger, represents Similarity value higher.Similarity expression formula is:
Formula(8)
WhereinFor Euclidean distance expression formula, xiRepresent i-th in the corresponding sparse solution of test image Sparse coefficient on individual position, mxFor the position that greatest coefficient is located;uiRepresent the dilute of the training image generic with test sample Discongest the sparse coefficient on i-th position, nuFor the position that its greatest coefficient is located.
Step 114:By the Similarity value for obtaining, arranged according to order from big to small, returned retrieval result;
Step 115:Terminate the SAR image search method of sparse coding classification.
As shown in Fig. 2
Described step 104, comprises the steps:
Step 201:Start to build complete dictionary and train sparse grader;
Step 202:Constructed complete dictionary:The corresponding characteristic vector of training image is arranged according to classification, it is identical The feature column vector of classification is discharged successively together, constructs the excessively complete dictionary A=[χ required for rarefaction representation12,... χn], χiRepresent one type training sample, χi=[α12,...αk], the total classification number of training sample is n;
Step 203:Obtain the excessively complete dictionary in new local:By each the training sample in sample to be sorted and excessively complete dictionary This subtraction calculations residual values, set threshold value T, and residual values are proposed more than the training sample corresponding to threshold value, and composition is new The excessively complete dictionary A in local1=[χ12,...χk];
Step 204:Using based on the dilute optimization method y=Ax of dual Local Search Memetic Algorithm for Solving, sparse solution is obtained X, y is original test image in optimization method, and A is the excessively complete dictionary of training image composition, and x is the corresponding sparse solutions of y;
In an embodiment of the present invention, the sparse solution for arriving of solving-optimizing equation is as shown in Figure 3;
Step 205:Design classification function δi,(δi∈Rm×n), coefficients all kinds of in sparse solution x are proposed respectively, construct new Sparse solution δi(x).The coefficient value for there was only a class in new sparse solution is not zero, and the value of remainder is zero;Therefore, press Test sample is reconstructed according to below equation
Formula(9)
The process simplification of final image classification is the following problem of solution:
Formula(10)
Wherein, | | | |1Represent L1- norm, | | | |2Represent L2- norm, A is the excessively complete dictionary of training image composition.
Calculate original sample y to be sorted and reconstructed sampleTwo poor norms, the classification that the minima for obtaining is located is The classification that test sample belongs to;
Step 206:Terminate the process of the sparse grader of training;
As shown in figure 4,
Described step 204, comprises the steps:
Step 301:Start with based on the dilute optimization method of Memetic Algorithm for Solving of dual Local Search, obtain sparse Solution;
Step 302:The selection of individuality and coding, by the excessively complete dictionary A in local1In training sample position as individuality Encoded, coded system adopts decimal coded mode, if including five sample positions in each individuality;
In an embodiment of the present invention, five positions are encoded per each individuality of class sample to be sorted, are included per a generation 50 individualities, calculated altogether for 200 generations, and its coded system is as shown in Figure 5.
Step 303:The corresponding training sample of five coding sites is proposed into the new dictionary A of composition2, calculated using match tracing Method-MP, solving-optimizing problem y=Ax obtains the sparse coefficient under the dictionary;
Step 304:The selection of fitness function:By sample y to be sorted and reconstructed sampleDifference two norms be set to adapt to Degree function, the value of two norms is less to represent that fitness is higher;
Step 305:Judge whether fitness value meets first end condition-residual values less than setting value or reach most Big iterationses, if meeting, jump directly to step 310, otherwise continue executing with step 306;
Step 306:Select, sample is selected according to the height of fitness value, retain excellent individual, i.e. fitness compared with High individuality;
Step 307:Intersect, the mode of intersection is handed over the part behind cross point to randomly generate a cross point Change, two adjacent individualities intersect two-by-two, and in an embodiment of the present invention, crossover probability is set to 0.6;
Step 308:Variation, the mode of variation enters row variation to randomly select single-point, in an embodiment of the present invention, variation Probability is set to 0.01;
Step 309:First stage Local Search, when obtaining preferably individual after each iteration, in local dictionary A1In Using the neighborhood position of left and right n of each position as Local Search candidate constituency, again according to the height of fitness in candidate regions It is low to be selected, update existing more excellent individuality;After first stage Local Search is completed, global search process steps are returned to 304, individual fitness value is calculated, carry out the judgement of next execute instruction;
In an embodiment of the present invention, using the neighborhood position of left and right n of each position in individuality as Local Search candidate Constituency, selection mode is as shown in Figure 6;
Step 310:The Local Search of second stage, after all iterative process are completed, according to the search in step 309 Method, in whole excessively complete dictionary A a Local Search is carried out again;
Step 311:Judge whether to meet end condition-residual values less than setting value or reach maximum iteration time, if full Foot carries out step 312, otherwise return to step 310;
Step 312:The final global optimum for meeting condition of output is individual, and the position in individuality is required for us The position that sparse coefficient is located;
Step 313:Terminate the process using the Memetic Algorithm for Solving sparse solutions based on dual Local Search.
Part of the present embodiment without detailed narration belongs to the known conventional means of the industry, does not describe one by one here.
The effect of the present invention can be further illustrated by following emulation experiment:
1. experiment condition and content:
Experiment condition:
It is core22.4GHZ, emulated using Matlab2010 in internal memory 2G, WINDOWSXP system in CPU.
Experiment content:
Present invention experiment SAR image storehouse used includes 5 class SAR images, respectively cities and towns, farmland, bridge, mountains and rivers and water Domain, image size is 256 × 256, and sum is respectively 560,633,367,600,600, as shown in Figure 7.In every class image with Machine selects 200 width as training image, and remaining is used as test image.
(1) comparison of accuracy of classifying:Respectively use set forth herein algorithm and orthogonal matching pursuit algorithm, least square Method, step is moved orthogonal matching pursuit algorithm, base tracing algorithm, Memetic algorithms etc. and carries out image classification, the final classification knot of comparison Really.
(2) precision ratio of SAR image retrieval is calculated:
Recall ratio and the standard evaluation methodology that precision ratio is in information retrieval, are increasingly used and are based on now In the middle of the image retrieval of content, herein using precision ratio as retrieval result evaluation criterion, it reflect retrieval result it is accurate Property.Then precision ratio is defined as:
Formula(11)
Wherein, Q represents whole image data base, and A represents the set of associated picture, and B represents the image collection for retrieving.
2. experimental result:
(1) this 5 class SAR image is classified with above-mentioned carried method, as a result as shown in fig. 7, wherein green line generation Classification results of the table based on orthogonal matching pursuit algorithm;Blue line is represented based on the classification results of method of least square;Black line is The result that base method for tracing is obtained;Yellow line is that step moves the result that orthogonal matching pursuit algorithm is obtained;Red line be based on The classification results of Memetic algorithms;Pink colour line is the proposed Memetic based on dual Local Search and sparse coding Method obtained by classification results.
Knowable to Comparative result table 1, evolution algorithm can play preferable effect, phase in the optimization problem of image classification Than Memetic algorithm, it is proposed that method can obtain higher classification accuracy, and robustness is higher.Concrete classification Accuracy is (%):
Table 1
(2) use set forth herein the result of SAR image retrieval that obtains of method as shown in table 2, calculate per class SAR image To precision ratio be:
Table 2
In summary, set forth herein method solve the problems, such as SAR image retrieve when, classification accuracy, retrieve phase Like property, computation complexity, as a result preferably effect is all served in terms of robustness.

Claims (2)

1. the SAR image search method based on sparse coding classification, is characterized in that:At least comprise the steps:
Step 101:Start based on the SAR image retrieval of sparse coding classification;
Step 102:Training image to be chosen in SAR image storehouse, these images are read in, each image size of selection is 256 × 256, and the method filtered using exquisite Lee carries out pretreatment to it, reduces what coherent speckle noise was caused to image classification result Affect, the window size of wave filter is set as 7 × 7;
Step 103:Feature extraction is carried out using the method for gray level co-occurrence matrixes to pretreated training image, 0 ° is chosen, 45 °, 90 °, the energy, entropy, contrast, local similarity, related each five features on 135 ° of directions, each width training image pair The column vector that dimension is 20 should be obtained;
If pij(d, θ) is represented in given space length d and direction θ, with gray scale i as initial point, the probability of gray level j, i=is occurred 1,2 ..., G, j=1,2 ..., G, G are the maximum of gray level in institute's image under consideration region, then gray level co-occurrence matrixes are a G The square formation of × G, note
The value of θ is set as 0 °, 45 °, 90 °, 135 °, in order to obtain image textural characteristics in all directions, to above-mentioned 4 Individual direction constructs respectively gray level co-occurrence matrixes and extracts corresponding characteristic vector;From feature include following five kinds of features:
1) energy, also known as angular second moment:
It is the tolerance of gradation of image distributing homogeneity or flatness, when in gray level co-occurrence matrixes Elemental redistribution relatively concentrate on lead it is right When near linea angulata, gradation of image distribution uniform in regional area is illustrated, image is presented thinner texture, the value of angular second moment It is larger;
2) entropy:
Entropy is the tolerance that image has quantity of information, is the characteristic parameter for measuring grey level distribution randomness, characterizes image The complexity of middle texture;The gray scale of image is more uniform, and entropy is less, and the texture of image is more complicated, and entropy is then bigger;The opposing party Face, entropy can also measure the randomness of image texture, and entropy is bigger, and gray scale distribution randomness is big in representative image;
3) contrast, also known as the moment of inertia:
Local gray level change total amount in its phenogram picture, reflects the definition of image and the rill depth of texture;Texture Rill depth, contrast is big, and effect is clear;Conversely, contrast is little, then rill is shallow, and effect is obscured;That is, if the deviation from right The unit of linea angulata have higher value, i.e. gradation of image value changes quickly, then contrast value has larger value;
4) local similarity:
Local similar performance portrays the textural characteristics of regional area, is to discriminate between the important measure of different target;
5) it is related
Wherein,
Therefore, after gray level co-occurrence matrixes have been calculated, each image can obtain 20 features, i.e. dimensionality reduction to a dimension be 20 Column vector;
Step 104:Complete dictionary was constituted using the characteristic vector obtained in step 103, sparse grader was trained;
Step 105:Whole SAR picture libraries are classified using the sparse grader for training;
Step 106:The category and corresponding sparse solution of each image in storage SAR image storehouse;
Step 107:Import test SAR image, it is desirable to which its size is equal in magnitude with the SAR image in image library, according to step 102 In method process is filtered to test image;
Step 108:Method according to the gray level co-occurrence matrixes in step 103 carries out feature extraction to test image, obtains corresponding 20 features;
Step 109:Test image is judged whether in the SAR image storehouse that step 106 is obtained, if so, then directly carry out step 110, otherwise into step 111;
Step 110:Directly extract and test image identical SAR image in the SAR image storehouse for having category;
Step 111:Test image is classified using the sparse grader for training before;
Step 112:The class label and its corresponding sparse solution of storage test image;
Step 113:The image of identical category is proposed in the SAR image storehouse for having category according to the classification of test image, figure is carried out As similarity mode;Test image and the Euclidean distance of the sparse solution of generic image are calculated first, are then found in sparse solution The position that greatest coefficient is located, calculates the difference of two positions, and the module of similarity is set as Euclidean distance and position difference Product absolute value inverse, be worth bigger, represent that Similarity value is higher, similarity expression formula is:
WhereinFor Euclidean distance expression formula, xiRepresent i-th in the corresponding sparse solution of test image Sparse coefficient on individual position, mxFor the position that greatest coefficient is located;uiRepresent the dilute of the training image generic with test sample Discongest the sparse coefficient on i-th position, nuFor the position that its greatest coefficient is located,
Step 114:By the Similarity value for obtaining, arranged according to order from big to small, returned retrieval result;
Step 115:Terminate the SAR image search method of sparse coding classification;
Described step 104, comprises the steps:
Step 201:Start to build complete dictionary and train sparse grader;
Step 202:Constructed complete dictionary:The corresponding characteristic vector of training image is arranged according to classification, identical category Feature column vector discharge successively together, construct the excessively complete dictionary A=[x required for rarefaction representation1, x2..., xn], χiRepresent one type training sample, xi=[a1, a2..., ak], the total classification number of training sample is n;
Step 203:Obtain the excessively complete dictionary in new local:By each the training sample phase in sample to be sorted and excessively complete dictionary Subtract calculating residual values, set threshold value T, residual values are proposed more than the training sample corresponding to threshold value, constitute new office The excessively complete dictionary A in portion1=[x1, x2..., xn1];
Step 204:Using based on the dilute optimization method y=Ax of dual Local Search Memetic Algorithm for Solving, sparse solution x is obtained, it is excellent It is original test image to change y in equation, and A is the excessively complete dictionary of training image composition, and x is the corresponding sparse solutions of y;
Step 205:Design classification function δi, (δi∈Rm×n), all kinds of coefficients in sparse solution x are proposed respectively, construct new dilute Discongest δiX (), the coefficient value for there was only a class in new sparse solution is not zero, the value of remainder is zero;Therefore, according to Lower expression re-formation goes out test sample
The process simplification of final image classification is the following problem of solution:
Wherein, | | | |1Represent L1- norm, | | | |2Represent L2- norm, A is the excessively complete dictionary of training image composition;
Calculate original sample y to be sorted and reconstructed sampleTwo poor norms, the classification that the minima for obtaining is located is test specimens Originally the classification for belonging to;
Step 206:Terminate the process of the sparse grader of training.
2. the SAR image search method classified based on sparse coding according to claim 1, is characterized in that:Described step Rapid 204, comprise the steps:
Step 301:Start with based on the dilute optimization method of Memetic Algorithm for Solving of dual Local Search, obtain sparse solution;
Step 302:The selection of individuality and coding, by the excessively complete dictionary A in local1In the position of training sample carry out as individuality Coding, coded system adopts decimal coded mode, if including five coding sites in each individuality;
Step 303:The corresponding training sample of five coding sites is proposed into the new dictionary A of composition2, using matching pursuit algorithm- MP, solving-optimizing problem y=Ax obtains the A2Sparse coefficient under dictionary;
Step 304:The selection of fitness function:By sample y to be sorted and reconstructed sampleTwo norms of difference be set to fitness letter Number, the value of two norms is less to represent that fitness is higher;
Step 305:Judge whether fitness value meets first end condition-residual values less than setting value or reach maximum and change Generation number, if meeting, jumps directly to step 310, otherwise continues executing with step 306;
Step 306:Select, sample is selected according to the height of fitness value, retain excellent individual, i.e. fitness higher It is individual;
Step 307:Intersect, the mode of intersection swaps the part behind cross point, phase to randomly generate a cross point Adjacent individuality intersects two-by-two, and crossover probability is set to 0.6;
Step 308:Variation, the mode of variation enters row variation to randomly select single-point, and mutation probability is set to 0.01;
Step 309:First stage Local Search, when obtaining preferably individual after each iteration, in local dictionary A1It is middle by each The neighborhood position of left and right n of position is selected as Local Search candidate regions, the height again according to fitness in candidate regions Select, update existing more excellent individuality;After first stage Local Search is completed, global search process steps 304 are returned to, calculate individual The fitness value of body, carries out the judgement of next execute instruction;
Step 310:The Local Search of second stage, after all iterative process are completed, according to the side of the search in step 309 Method, in whole excessively complete dictionary A a Local Search is carried out again;
Step 311:Judge whether to meet end condition-residual values less than setting value or reach maximum iteration time, if meet into Row step 312, otherwise return to step 310;
Step 312:The final global optimum for meeting condition of output is individual, and the position in individuality is sparse required for us The position that coefficient is located;
Step 313:Terminate the process using the Memetic Algorithm for Solving sparse solutions based on dual Local Search.
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