JP2013105373A - Device, method, and program for data acquisition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire data suitable for recognition of a target object from a set of images.SOLUTION: Clusters are generated per local feature quantity of an image first selected from a set of images given as images relating to a target object, on the basis of this image, and local feature quantities of images selected subsequently are classified into the clusters of similar feature quantities to update the clusters, and an image and feature quantities of an extraction source are acquired as data for object recognition on the basis of clusters having larger numbers of elements. Since importance is attached to general features common to many images and minor features are ignored, data suitable for target object recognition can be acquired from the set of images. In particular, first selecting an appropriate image correctly orients classification to clusters to lead to the improvement in accuracy of object recognition.

Description

  The present invention relates to recognition of an object.

  In the field of so-called object recognition in which objects (for example, buildings, articles, people, faces, animals and plants, and other various objects) are recognized from images by a computer, a plurality of images including objects to be recognized are prepared and learned. It is known that the accuracy of recognition can be improved by making it. Then, in order to collect a large amount of images including the target object as learning data, “Yahoo! Search (image)” (see Non-Patent Document 1) using the name of the target object as a query, that is, a search keyword, etc. Image search is available. In addition, as in Patent Document 1, a technique is also known in which an image, that is, a query image is used as a search key instead of a keyword, and learning examples, that is, learning data are collected by similar image search.

JP 2010-92413 A

Yahoo Japan Corporation, "Yahoo! Search (image)", [online], [October 14, 2011 search], Internet <URL: http://image-search.yahoo.co.jp/>

  However, an image set collected by an image search or the like based on a keyword often includes images in which the target object is not necessarily properly captured. Examples of inappropriate images include images that are related to the subject but are completely different, a night view that does not clearly show objects, images that show other elements of the landscape, partially enlarged images, special viewpoints and techniques, special There are a wide variety of images such as images produced by visual effects. If these image sets that still contain inappropriate images are used as learning data, the accuracy of object recognition decreases, so acquisition of accurate learning data is an important issue.

  In this regard, the technique disclosed in Patent Document 1 has a fixed feature amount serving as a collection reference, and the collected image depends on the query image, so there is a limit to the accuracy of the learning data.

  In view of the above problems, an object of the present invention is to obtain learning data that improves the accuracy of object recognition.

  Based on the above object, a data acquisition device according to one aspect (1) of the present invention includes a feature amount extraction unit that sequentially selects an image from an image set and extracts a plurality of local feature amounts from the image, and the image set. For each local feature extracted from the initially selected image, cluster generation means for generating a cluster, and the feature value of the cluster is calculated from all elements classified into each cluster, and set for each cluster Each time an image is selected from the image set, the local feature value extracted from the image is more than a predetermined number of local feature values that approximate the feature value of the cluster. A cluster updating means for updating the cluster by classifying the local feature amount into a cluster in which the approximate feature value is set, and for object recognition based on the cluster having a large number of elements. A data acquisition means for acquiring data, comprising the.

  A data acquisition method according to another aspect (7) of the present invention is a method of extracting the plurality of local feature amounts from the image by sequentially selecting the images from the image set by capturing the above aspects in the method category. Processing, cluster generation processing for generating a cluster for each local feature extracted from the image initially selected from the image set, and calculation of feature values of the cluster from all elements classified into each cluster Then, each time an image is selected from the image set, the local feature value that approximates the feature value of the cluster among the local feature values extracted from the image each time the image is selected from the image set Is equal to or greater than a predetermined number, the cluster update processing for updating the cluster by classifying the local feature amount into clusters set with the approximate feature value, and the cluster having a large number of elements. , Characterized in that the data acquisition process for acquiring data for object recognition, the computer executes.

  Another aspect (8) of the present invention is a data acquisition computer program that captures the above aspect in the category of a computer program. The computer sequentially selects images from a set of images, and selects a plurality of local images from the image. A feature amount is extracted, a cluster is generated for each local feature amount extracted from the image first selected from the image set, and a feature value of the cluster is calculated from all elements classified into each cluster. Each time an image is selected from the image set, the local feature value approximated to the cluster feature value out of the local feature values extracted from the image is greater than or equal to a predetermined number. For example, the local feature amount is classified into a cluster in which the approximate feature value is set to update the cluster, and based on the cluster having a large number of elements, the object Characterized in that to obtain the data for the defect recognition.

  In the above aspect of the present invention, a cluster is generated for each local feature amount based on an image first selected from an image set given as related to the target object, and the local feature amount of the image selected thereafter is determined. Then, the cluster is updated by classifying it into approximate feature value clusters, and the image and the feature value of the extraction source are obtained as object recognition data based on the cluster having a large number of elements.

  As a result, general features common to many images are emphasized and minority features are ignored, so that data suitable for recognition of the target object can be obtained from the image set. In particular, if an appropriate image is selected first, the classification into clusters can be correctly oriented, and the accuracy of object recognition can be improved.

  According to another aspect (2) of the present invention, in any one of the above aspects, the cluster updating unit does not have the feature value that approximates the local feature amount extracted from the image selected after the second time. In the case, a cluster corresponding to the local feature is generated.

  In another aspect (3) of the present invention, in any one of the above aspects, the cluster updating unit updates the cluster updated based on the image of the image set again based on the image of the same image set. It is characterized by that.

  According to another aspect (4) of the present invention, in any one of the above aspects, the data acquired by the data acquisition unit is used as candidate data, and an image based on the candidate data is removed from the image set as a new image set. On the other hand, the re-execution unit that acquires new candidate data by the feature amount extraction unit, the cluster generation unit, the feature value setting unit, the cluster update unit, and the data acquisition unit is compared with the acquired candidate data. And a result selection means for selecting data having a large number of images as final object recognition data.

  According to another aspect (5) of the present invention, in any one of the aspects described above, the data acquisition unit may extract the image from which the local feature amount classified into the cluster having a large number of elements is extracted as an object. It is acquired as learning data for recognition.

  According to another aspect (6) of the present invention, in any one of the above aspects, the data acquisition unit acquires the feature value of the cluster having a large number of elements as the data for object recognition. .

  Each of the above aspects can also be understood as other categories (methods, programs, systems, etc.) that are not specified. For the method and program categories, the “means” indicated in the device category is used as the “processing”. "Or" step ". Further, the order of processes and steps is not limited to the one directly specified in the present application, and can be changed such as changing the order or executing some processes collectively or partly at any time.

  In addition, computers such as terminals that implement and execute individual means, processes, and steps may be common, or may differ for each means, process, step, or timing. Further, all or any part of the “means” can be read as “part” (unit, section, module, etc.).

  According to the present invention, it is possible to obtain learning data that improves the accuracy of object recognition.

The functional block diagram which shows a structure about embodiment of this invention. The figure which shows the example of data in embodiment of this invention. The flowchart which shows the process sequence in embodiment of this invention. The conceptual diagram which shows the image set in embodiment of this invention. The conceptual diagram which shows the classification | category to the cluster in embodiment of this invention.

  Next, a mode for carrying out the present invention (referred to as “embodiment”) will be illustrated along the drawings. In addition, the assumptions common to the contents already described in the background art and problems are omitted as appropriate.

[1. Constitution〕
The present embodiment relates to the data acquisition device 1 (hereinafter also referred to as “this device 1” or “this device”) shown in the configuration diagram of FIG. 1, and this device 1 has at least an arithmetic operation such as a CPU as a computer configuration. Communication means 8 (mobile communication network) between the control unit 6, a storage device 7 such as a main memory or an auxiliary storage device, and a communication network N (for example, a mobile communication network such as a mobile phone, PHS, public wireless LAN, or the Internet) Communication circuit, wireless LAN adapter, and the like.

  In the present apparatus 1, elements (20, 30, etc.) such as each unit shown in FIG. 1 are realized by the arithmetic control unit 6 executing a predetermined computer program stored in the storage device 7. Of the elements to be realized, the mode of the information storage means is arbitrary, and can be realized in any data format such as a file on the storage device 7, or may be remote storage by network computing (cloud).

  The storage means may include not only a data storage area but also functions such as data input / output and management. In addition, the unit of the storage means shown in this application is for convenience of explanation, and the configuration can be divided or integrated as appropriate, and the processing data and processing results of each means are stored in addition to the explicit storage means. A storage means is used as appropriate.

  In the flow chart of the present application and the like, the cylindrical figure representing the storage means does not mean limitation to direct access storage, and the hexagon represents determination rather than preparation. In addition, the arrows in the figure (for example, FIG. 1) supplementarily indicate the main direction of the flow of data, control, etc., and do not deny other flows or imply a limitation on the direction. For example, before or after data acquisition in a certain direction, a data request or an acknowledgment (ACK) can occur in the reverse direction.

  In addition, each means other than the storage means is a processing means for realizing and executing the functions and operations of information processing as described below, but these are functional units arranged for explanation, and actual hardware It doesn't matter if it matches elements or software modules.

[2. Effect)
A processing procedure in the apparatus 1 configured as described above is shown in a flowchart of FIG.

[2-1. Overview〕
First, only the outline is extracted and described from FIG. 3. The feature amount extraction unit 20 sequentially selects images from the image set stored in the image set storage unit 15 and extracts a plurality of local feature amounts from the image. (Step S11). Then, the cluster generation unit 30 generates a cluster for each local feature amount extracted from the image first selected from the image set (step S12). Further, the feature value setting means 40 calculates the feature value of the cluster from all the elements classified into each cluster and sets it in each cluster (step S19).

Then, each time an image is selected from the image set S, the cluster updating unit 50 determines whether or not the local feature value approximated to the cluster feature value is greater than or equal to a predetermined number for the local feature value extracted from the image (step S13). If this is the case (step S15: “YES”), the cluster is updated by classifying the local feature amount into clusters in which the approximate feature value is set (step S16). As a result of the update, the data acquisition unit 60 finally acquires object recognition data based on a cluster having a large number of elements (for example, a predetermined ratio or more) (step S22).
Each process will be specifically described below.

[2-2. (Image selection and cluster generation)
First, at the beginning of the processing for a given image set S, the feature amount extraction means 20 selects one image (for example, image a) from the image set S, and selects a local feature amount (for example, SIFT) from the image a. ) Is extracted (step S11). Here, the image set S may be given to the apparatus 1 by the operator via a storage medium or the like, but the apparatus 1 transmits the name of the object (for example, “Tokyo Tower”) to the image search server 2 or the like. The image set S may be received by receiving the search result images.

  Then, the cluster generation unit 30 generates a cluster for each local feature amount extracted from the image a first selected from the image set S (step S12). A cluster is configured by a set of local feature values, and data representing the cluster is stored in the cluster storage unit 35 (for example, FIG. 2), but a specific data configuration and a realization mode of registered contents are free.

  For example, if the number of elements for each cluster, that is, the number of local feature quantities classified into the cluster (“number of elements”) is stored as in the example of FIG. 2, deletion in units of clusters corresponding to the number of elements And data acquisition becomes easier. Note that the mode of associating clusters with local feature quantities classified into clusters is also free. For example, each cluster may have a list of local feature quantities, or conversely, for each extracted local feature quantity. Alternatively, it may have data such as a cluster ID indicating the classified cluster.

  Further, in the example of FIG. 5 (conceptual diagram), each cluster 01, 02, 03 has, for example, “there is an upward cusp” extracted from the image “a” (local feature amount a1 indicated by a dashed circle in FIG. 4). ), “There is a right-facing convex portion” (local feature amount a2 indicated by a broken-line circle in FIG. 4) is classified, but in practice, an extraction source image is shown for each local feature amount. It is possible to include identification information in the cluster data. Immediately after the generation of the cluster, one local feature is classified into each cluster, and the local feature also serves as the feature value of the cluster. The extracted local feature value and cluster feature value are subjected to processing such as matching in consideration of the coordinate position on the image. By using the positional relationship on the coordinates of the feature quantities whose values substantially coincide with each other in the collation of the coordinate positions, it is possible to cope with differences in angles and sizes in which the object is reflected in the image.

  Further, the cluster may be generated for each local feature extracted from a single image, but two images a and b are first selected from the image set S, and similarities extracted from the two images a and b are selected. It is desirable that the local feature quantities to be matched are matched by matching the coordinates using a matching method such as ransac, and a cluster is created for each local feature quantity associated by matching. In this case, if the number of local feature amounts associated with the cluster is large, it can be determined that the same object exists, and it can be estimated that the object exists in the coordinate region where the local feature amount is distributed.

  If the number of local features that can be associated between the images a and b selected first is zero or less than a predetermined value and it is considered that the same object does not exist, the image set S is used instead of the image a or b. Another image c is selected, and the extraction and association of the local feature amount are performed again. Alternatively, local feature amount matching may be performed on the entire image included in the set S.

[2-3. Classification and new generation of classes)
After generating a cluster at the beginning of the processing as described above, each time an image is selected from the image set S, the cluster updating unit 50 extracts the local feature (step S13) extracted from the image and all the clusters. The feature value is collated using the comparison of coordinates (step S14). That is, according to a matching method such as ransac, the presence / absence of an object can be determined by the positional relationship of coordinates having local feature amounts, and each local feature amount extracted from an image and each cluster using the matching method such as ransac Coordinates and values are collated with the feature values.

  As a result of the collation, if the local feature amount extracted from the image is equal to or greater than a predetermined number (or one) of the local feature amount that approximates the feature value of the cluster and matches the positional relationship of the coordinates (or may be one) ( Step S15: "YES"), the cluster is updated by classifying the local feature quantity into clusters set with the approximate feature value (Step S16). Considering the positional relationship between the coordinates of the local feature amount and the center of gravity of the coordinates on the image, which is the cluster feature value, in the determination of approximation, the determination accuracy of the image in which the same object exists is improved.

  Although a cluster is generated from the first selected image a (step S11) (step S12), the cluster updating unit 50 then selects a local feature amount extracted from the second and subsequent images (step S12). For those that are not classified into clusters in step S13) (step S17: “NO”), a cluster corresponding to the local feature is newly generated (step S18).

[2-4. (Feature value setting etc.)
Further, the feature value setting means 40 calculates the feature value of the cluster from all the elements classified into each cluster and sets it in each cluster (step S19). Specifically, for the local feature quantities classified for each cluster, the center of gravity in the feature amount space and the center of gravity at the coordinate position on the image are calculated and set as new feature values for each cluster. The center of gravity at the coordinate position on the image is based on the coordinate position of the first image to correspond to various image sizes and the rotation and reduction / enlargement of the object in the image. Normalize coordinates after calculating rate.

  By using these centroids as cluster feature values, it is based on what local features (centroids in the feature space) are in the image (centroids at the coordinate positions on the image). Can be classified into clusters. In particular, the processing accuracy is improved by including the coordinate position on the image for the local feature amount in the determination.

  The above processing is repeated until the unprocessed image is exhausted (step S20: “NO”), and then the process proceeds to acquisition of data for object recognition (step S22). Prior to that, the number of elements in the cluster is equal to or less than a predetermined value. May be deleted (step S21). Thereby, for example, when the cluster is re-updated as described below, the processing capability can be concentrated on the main features by excluding the features that exist in a small number from the classification targets.

[2-5. (Renew cluster)
Further, since the feature value of the cluster fluctuates depending on the image selection order in step S13, the processing from step S13 shown in FIG. For example, it is possible to generate feature values that accurately represent the characteristics of an object. In this case, the cluster update unit 50 updates the cluster updated based on the images of the image set again based on the images of the same image set.

[2-6. Data acquisition mode]
As a result of updating the clusters as described above, the data acquisition unit 60 finally acquires data for object recognition based on a cluster having a large number of elements (for example, a predetermined ratio or more) (step S22).

  Although the specific content and format of the data for object recognition are arbitrary, the first example is that the data acquisition means 60 is the source of extraction from which the local feature quantities classified into clusters with a large number of elements are extracted. An image is acquired as learning data for object recognition.

  For example, if an image a is first selected from the image set S in FIG. 4, images a, c, and f in which the target object (for example, “OO tower”) is clearly shown are to be acquired. An image b in which only a part of “XX Tower” is shown, an image d in which the night view is indistinct, an image e in which a part of the scenery is shown, and an image g in which other objects are more prominent are obtained. (It is indicated with a cross for explanation).

  The second example regarding the data for object recognition is that the data acquisition means 60 acquires the feature value of the cluster having a large number of elements or the local feature amount classified into the cluster as the data for object recognition. In the state of the example in FIG. 5, for example, the feature value of the cluster 02 having the largest number (three) of elements (for example, the centroid on the feature amount space and the centroid at the coordinate position on the image) is used for object recognition. It becomes data.

[2-7. (Multiple acquisition of candidate data)
In order to further improve the object recognition accuracy, it is conceivable to acquire a plurality of object recognition data. In this case, the re-execution means 70 uses the data acquired by the data acquisition means as candidate data, and the feature quantity extraction means 20, cluster generation for the new image set obtained by removing the image based on the candidate data from the image set. New candidate data is acquired by the means 30, the feature value setting means 40, the cluster update means 50, and the data acquisition means 60.

  After that, the result selection means 80 compares the candidate data acquired first and the newly acquired candidate data, and selects the one with a large number of images as the final object recognition data.

[3. effect〕
(1) As described above, in the present embodiment, a cluster (for example, FIG. 5 and FIG. 2) is generated for each local feature amount based on an image first selected from an image set given as related to a target object. (For example, step S12 in FIG. 3), the local feature amount of the image selected after that (step S13) is classified into clusters of approximate feature values, and the cluster is updated (steps S14 to S16). Based on the large number of clusters, the source image and feature values are obtained as object recognition data (step S22).

  As a result, features common to objects are emphasized, minority features are ignored, and data for recognition is collected. Therefore, data suitable for object recognition can be obtained from the image set. In particular, if an appropriate image is selected first, classification into clusters can be correctly oriented, and the accuracy of data used for object recognition can be improved.

(2) In particular, in the present embodiment, when there is no cluster corresponding to the local feature amount of the image selected after the second (step S17: “NO”), by newly generating the corresponding cluster ( In step S18), a feature that may be included in another image can be a target of subsequent cluster classification, and a generation of a cluster representing the feature of the object can be prevented, thereby improving the accuracy of object recognition. it can.

(3) Further, in the present embodiment, the cluster is updated as the second round based on the same image set with respect to the cluster classified in the first round based on the image set. As a result, the feature value of the cluster is obtained by utilizing the state that is established to some extent in the first round with respect to the center of gravity in the feature amount space for each cluster and the center of gravity on the image coordinates, which are the criteria for determining the local feature approximation. Can be reflected in the cluster classification with higher accuracy, so that the object recognition accuracy can be further improved.

(4) Further, in this embodiment, the re-execution unit 70 acquires another candidate data from the image set excluding the candidate data by further processing, and the result selection unit 80 compares the two candidate data. Those having a large number of images are selected as final object recognition data.

  As a result, even if an object different from the target object is accidentally shown in the first selected image, candidate data in which more images showing the target object remain is used as final object recognition data. be able to. For this reason, by selecting candidate data having a larger number of images, a correct processing result can be obtained, and object recognition can be improved.

(5) In addition, in the present embodiment, an image (for example, the images a, c, and f in FIG. 7) from which the local feature amount added to the cluster having a large number of elements is extracted is used for learning for object recognition. By acquiring as data, an arbitrary algorithm can be flexibly applied to actual object recognition on the basis of these images according to circumstances such as usage.

(6) In particular, in the present embodiment, the feature values of a cluster having a large number of elements (for example, cluster 02 in FIG. 5) are acquired as object recognition data, so that the data can be smoothly recognized as a recognition target in actual object recognition. It becomes possible to utilize.

[4. Other embodiments]
In addition, the said embodiment is only an illustration and this invention includes what is illustrated below and other embodiment other than that. For example, the configuration diagrams, data diagrams, flowcharts, and the like in the present application are merely examples, and the presence / absence of each element, the order of the arrangement and processing execution, and the specific contents can be changed as appropriate. For example, for the image to be initially selected in step S11, a plurality of images may be selected as candidates. Specifically, an image selected as a candidate is used as a reference image, and a local feature amount is compared between the reference image and each image in the set S (processing in step S15). Is the first image, learning data can be obtained using an image in which a more standard object exists.

  In addition, the mode for realizing the individual means constituting the apparatus 1 is free, and functions provided by an external server are called by API (application program interface) or network computing (so-called cloud). For example, the configuration of the present invention can be flexibly changed. Furthermore, each element such as means relating to the present invention may be realized by other information processing mechanisms such as a physical electronic circuit as well as a computer control unit.

01, 02, 03 Each cluster 1 Data acquisition device 2 Image search server 6 Arithmetic control unit 7 Storage device 8 Communication means 15 Image set storage means 20 Feature quantity extraction means 30 Cluster generation means 35 Cluster storage means 40 Feature value setting means 50 Cluster Update means 60 Data acquisition means 70 Re-execution means 80 Result selection means a to g Images a1, a2, a3, c1, c2, d2, d3 Local feature amount N Communication network S Image set

Claims (8)

Feature amount extraction means for sequentially selecting images from the image set and extracting a plurality of local feature amounts from the images;
Cluster generation means for generating a cluster for each local feature extracted from the image initially selected from the image set;
Feature value setting means for calculating the feature value of the cluster from all elements classified into each cluster and setting the feature value in each cluster;
Each time an image is selected from the image set, if the local feature value approximated to the feature value of the cluster is greater than or equal to a predetermined number among the local feature values extracted from the image, the local feature value is Cluster updating means for updating the cluster by classifying the cluster with the feature value to be approximated, and
Data acquisition means for acquiring data for object recognition based on the cluster having a large number of elements;
A data acquisition device comprising: The cluster update means includes
The cluster corresponding to the local feature is generated when there is no feature value that approximates the local feature extracted from the image selected after the second time. Data acquisition device.   3. The data acquisition apparatus according to claim 1, wherein the cluster updating unit updates the cluster updated based on the image of the image set again based on the image of the same image set. The data acquired by the data acquisition unit is set as candidate data, and the feature amount extraction unit, the cluster generation unit, and the feature value setting are performed on a new image set obtained by removing an image based on the candidate data from the image set. Means, re-execution means for acquiring new candidate data by the cluster update means and the data acquisition means,
A result selection means for comparing the acquired candidate data and selecting a large number of images as final object recognition data;
The data acquisition device according to any one of claims 1 to 3, further comprising:   2. The data acquisition unit acquires the source image from which the local feature amount classified into the cluster having the large number of elements is extracted as learning data for object recognition. 5. The data acquisition device according to any one of items 4 to 4.   6. The data acquisition apparatus according to claim 1, wherein the data acquisition unit acquires the feature value of the cluster having a large number of elements as the data for object recognition. Feature amount extraction processing for sequentially selecting images from an image set and extracting a plurality of local feature amounts from the images;
Cluster generation processing for generating a cluster for each local feature extracted from the image initially selected from the image set;
Calculating a feature value of the cluster from all elements classified into each cluster, and setting the feature value in each cluster;
Each time an image is selected from the image set, if the local feature value approximated to the feature value of the cluster is greater than or equal to a predetermined number among the local feature values extracted from the image, the local feature value is Cluster update processing to update the cluster by classifying the cluster with the approximate feature value, and
Based on the cluster having a large number of elements, a data acquisition process for acquiring data for object recognition;
A data acquisition method characterized in that a computer executes. On the computer,
Select images sequentially from the image set and extract multiple local features from the images.
Generating a cluster for each of the local features extracted from the image initially selected from the image set;
The feature value of the cluster is calculated from all elements classified into each cluster, and is set for each cluster.
Each time an image is selected from the image set, if the local feature value approximated to the feature value of the cluster is greater than or equal to a predetermined number among the local feature values extracted from the image, the local feature value is Update the clusters by classifying them into clusters with approximate feature values,
A computer program for data acquisition, characterized in that data for object recognition is acquired based on the cluster having a large number of elements.

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