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

```
public class BOWImgDescriptorExtractor
extends java.lang.Object
```
Class to compute an image descriptor using the *bag of visual words*. Such a computation consists of the following steps: 1. Compute descriptors for a given image and its keypoints set. 2. Find the nearest visual words from the vocabulary for each keypoint descriptor. 3. Compute the bag-of-words image descriptor as is a normalized histogram of vocabulary words encountered in the image. The i-th bin of the histogram is a frequency of i-th word of the vocabulary in the given image.

Field Summary

Fields
Modifier and Type Field Description

protected long nativeObj

Constructor Summary

Constructors
Modifier	Constructor	Description
`protected`	`BOWImgDescriptorExtractor(long addr)`
	`BOWImgDescriptorExtractor(Feature2D dextractor, DescriptorMatcher dmatcher)`	The constructor.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static BOWImgDescriptorExtractor`	`__fromPtr__(long addr)`
`void`	`compute(Mat image, MatOfKeyPoint keypoints, Mat imgDescriptor)`
`int`	`descriptorSize()`	Returns an image descriptor size if the vocabulary is set.
`int`	`descriptorType()`	Returns an image descriptor type.
`protected void`	`finalize()`
`long`	`getNativeObjAddr()`
`Mat`	`getVocabulary()`	Returns the set vocabulary.
`void`	`setVocabulary(Mat vocabulary)`	Sets a visual vocabulary.

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

- Field Detail
  - nativeObj
```
protected final long nativeObj
```
- Constructor Detail
  - BOWImgDescriptorExtractor
```
protected BOWImgDescriptorExtractor(long addr)
```
  - BOWImgDescriptorExtractor
```
public BOWImgDescriptorExtractor(Feature2D dextractor,
                                 DescriptorMatcher dmatcher)
```
    The constructor.
    
    Parameters:
    
    dextractor - Descriptor extractor that is used to compute descriptors for an input image and its keypoints.
    
    dmatcher - Descriptor matcher that is used to find the nearest word of the trained vocabulary for each keypoint descriptor of the image.
- Method Detail
  - getNativeObjAddr
```
public long getNativeObjAddr()
```
  - __fromPtr__
```
public static BOWImgDescriptorExtractor __fromPtr__(long addr)
```
  - setVocabulary
```
public void setVocabulary(Mat vocabulary)
```
    Sets a visual vocabulary.
    
    Parameters:
    
    vocabulary - Vocabulary (can be trained using the inheritor of BOWTrainer ). Each row of the vocabulary is a visual word (cluster center).
  - getVocabulary
```
public Mat getVocabulary()
```
    Returns the set vocabulary.
    
    Returns:
    
    automatically generated
  - compute
```
public void compute(Mat image,
                    MatOfKeyPoint keypoints,
                    Mat imgDescriptor)
```
    Parameters:
    
    imgDescriptor - Computed output image descriptor. pointIdxsOfClusters[i] are keypoint indices that belong to the i -th cluster (word of vocabulary) returned if it is non-zero.
    
    image - automatically generated
    
    keypoints - automatically generated
  - descriptorSize
```
public int descriptorSize()
```
    Returns an image descriptor size if the vocabulary is set. Otherwise, it returns 0.
    
    Returns:
    
    automatically generated
  - descriptorType
```
public int descriptorType()
```
    Returns an image descriptor type.
    
    Returns:
    
    automatically generated
  - finalize
```
protected void finalize()
                 throws java.lang.Throwable
```
    Overrides:
    
    finalize in class java.lang.Object
    
    Throws:
    
    java.lang.Throwable

Class BOWImgDescriptorExtractor

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

nativeObj

Constructor Detail

BOWImgDescriptorExtractor

BOWImgDescriptorExtractor

Method Detail

getNativeObjAddr

__fromPtr__

setVocabulary

getVocabulary

compute

descriptorSize

descriptorType

finalize

fromPtr