DescriptorExtractor

java.lang.Object
- org.opencv.features2d.DescriptorExtractor

```
public class DescriptorExtractor
extends java.lang.Object
```
Abstract base class for computing descriptors for image keypoints.

class CV_EXPORTS DescriptorExtractor
// C++ code: public: virtual ~DescriptorExtractor(); void compute(const Mat& image, vector& keypoints, Mat& descriptors) const; void compute(const vector& images, vector >& keypoints, vector& descriptors) const; virtual void read(const FileNode&); virtual void write(FileStorage&) const; virtual int descriptorSize() const = 0; virtual int descriptorType() const = 0; static Ptr create(const string& descriptorExtractorType); protected:... };
In this interface, a keypoint descriptor can be represented as a

dense, fixed-dimension vector of a basic type. Most descriptors follow this pattern as it simplifies computing distances between descriptors. Therefore, a collection of descriptors is represented as "Mat", where each row is a keypoint descriptor.

See Also:
org.opencv.features2d.DescriptorExtractor : public Algorithm

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`BRIEF`
`static int`	`BRISK`
`static int`	`FREAK`
`static int`	`OPPONENT_BRIEF`
`static int`	`OPPONENT_BRISK`
`static int`	`OPPONENT_FREAK`
`static int`	`OPPONENT_ORB`
`static int`	`OPPONENT_SIFT`
`static int`	`OPPONENT_SURF`
`static int`	`ORB`
`static int`	`SIFT`
`static int`	`SURF`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`compute(java.util.List<Mat> images, java.util.List<MatOfKeyPoint> keypoints, java.util.List<Mat> descriptors)` Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant).
`void`	`compute(Mat image, MatOfKeyPoint keypoints, Mat descriptors)` Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant).
`static DescriptorExtractor`	`create(int extractorType)` Creates a descriptor extractor by name.
`int`	`descriptorSize()`
`int`	`descriptorType()`
`boolean`	`empty()`
`void`	`read(java.lang.String fileName)`
`void`	`write(java.lang.String fileName)`

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - BRIEF
```
public static final int BRIEF
```
    See Also:
    Constant Field Values
  - BRISK
```
public static final int BRISK
```
    See Also:
    Constant Field Values
  - FREAK
```
public static final int FREAK
```
    See Also:
    Constant Field Values
  - OPPONENT_BRIEF
```
public static final int OPPONENT_BRIEF
```
    See Also:
    Constant Field Values
  - OPPONENT_BRISK
```
public static final int OPPONENT_BRISK
```
    See Also:
    Constant Field Values
  - OPPONENT_FREAK
```
public static final int OPPONENT_FREAK
```
    See Also:
    Constant Field Values
  - OPPONENT_ORB
```
public static final int OPPONENT_ORB
```
    See Also:
    Constant Field Values
  - OPPONENT_SIFT
```
public static final int OPPONENT_SIFT
```
    See Also:
    Constant Field Values
  - OPPONENT_SURF
```
public static final int OPPONENT_SURF
```
    See Also:
    Constant Field Values
  - ORB
```
public static final int ORB
```
    See Also:
    Constant Field Values
  - SIFT
```
public static final int SIFT
```
    See Also:
    Constant Field Values
  - SURF
```
public static final int SURF
```
    See Also:
    Constant Field Values
- Method Detail
  - compute
```
public void compute(java.util.List<Mat> images,
           java.util.List<MatOfKeyPoint> keypoints,
           java.util.List<Mat> descriptors)
```
    Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant).
    
    Parameters:
    images - Image set.
    keypoints - Input collection of keypoints. Keypoints for which a descriptor cannot be computed are removed. Sometimes new keypoints can be added, for example: SIFT duplicates keypoint with several dominant orientations (for each orientation).
    descriptors - Computed descriptors. In the second variant of the method descriptors[i] are descriptors computed for a keypoints[i]. Row j is the keypoints (or keypoints[i]) is the descriptor for keypoint j-th keypoint.
    See Also:
    org.opencv.features2d.DescriptorExtractor.compute
  - compute
```
public void compute(Mat image,
           MatOfKeyPoint keypoints,
           Mat descriptors)
```
    Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant).
    
    Parameters:
    image - Image.
    keypoints - Input collection of keypoints. Keypoints for which a descriptor cannot be computed are removed. Sometimes new keypoints can be added, for example: SIFT duplicates keypoint with several dominant orientations (for each orientation).
    descriptors - Computed descriptors. In the second variant of the method descriptors[i] are descriptors computed for a keypoints[i]. Row j is the keypoints (or keypoints[i]) is the descriptor for keypoint j-th keypoint.
    See Also:
    org.opencv.features2d.DescriptorExtractor.compute
  - create
```
public static DescriptorExtractor create(int extractorType)
```
    Creates a descriptor extractor by name.
    
    The current implementation supports the following types of a descriptor extractor:
    - "SIFT" -- "SIFT"
    - "SURF" -- "SURF"
    - "BRIEF" -- "BriefDescriptorExtractor"
    - "BRISK" -- "BRISK"
    - "ORB" -- "ORB"
    - "FREAK" -- "FREAK"
    A combined format is also supported: descriptor extractor adapter name ("Opponent" -- "OpponentColorDescriptorExtractor") + descriptor extractor name (see above), for example: "OpponentSIFT".
    Parameters:
    extractorType - a extractorType
    See Also:
    org.opencv.features2d.DescriptorExtractor.create
  - descriptorSize
```
public int descriptorSize()
```
  - descriptorType
```
public int descriptorType()
```
  - empty
```
public boolean empty()
```
  - read
```
public void read(java.lang.String fileName)
```
  - write
```
public void write(java.lang.String fileName)
```

Class DescriptorExtractor

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

BRIEF

BRISK

FREAK

OPPONENT_BRIEF

OPPONENT_BRISK

OPPONENT_FREAK

OPPONENT_ORB

OPPONENT_SIFT

OPPONENT_SURF

ORB

SIFT

SURF

Method Detail

compute

compute

create

descriptorSize

descriptorType

empty

read

write