SURF (OpenCV 4.1.2 Java documentation)

java.lang.Object
- org.opencv.core.Algorithm
- - org.opencv.features2d.Feature2D
  - - org.opencv.xfeatures2d.SURF

```
public class SURF
extends Feature2D
```
Class for extracting Speeded Up Robust Features from an image CITE: Bay06 . The algorithm parameters:
- member int extended
  - 0 means that the basic descriptors (64 elements each) shall be computed
  - 1 means that the extended descriptors (128 elements each) shall be computed
- member int upright
  - 0 means that detector computes orientation of each feature.
  - 1 means that the orientation is not computed (which is much, much faster). For example, if you match images from a stereo pair, or do image stitching, the matched features likely have very similar angles, and you can speed up feature extraction by setting upright=1.
- member double hessianThreshold Threshold for the keypoint detector. Only features, whose hessian is larger than hessianThreshold are retained by the detector. Therefore, the larger the value, the less keypoints you will get. A good default value could be from 300 to 500, depending from the image contrast.
- member int nOctaves The number of a gaussian pyramid octaves that the detector uses. It is set to 4 by default. If you want to get very large features, use the larger value. If you want just small features, decrease it.
- member int nOctaveLayers The number of images within each octave of a gaussian pyramid. It is set to 2 by default.
Note:
- An example using the SURF feature detector can be found at opencv_source_code/samples/cpp/generic_descriptor_match.cpp
  - Another example using the SURF feature detector, extractor and matcher can be found at opencv_source_code/samples/cpp/matcher_simple.cpp

Field Summary
- Fields inherited from class org.opencv.core.Algorithm
  nativeObj

Constructor Summary

Constructors
Modifier Constructor and Description

protected SURF(long addr)

Constructors
Modifier	Constructor and Description
`protected`	`SURF(long addr)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static SURF`	`__fromPtr__(long addr)`
`static SURF`	`create()` 64-element descriptors).
`static SURF`	`create(double hessianThreshold)`
`static SURF`	`create(double hessianThreshold, int nOctaves)`
`static SURF`	`create(double hessianThreshold, int nOctaves, int nOctaveLayers)`
`static SURF`	`create(double hessianThreshold, int nOctaves, int nOctaveLayers, boolean extended)`
`static SURF`	`create(double hessianThreshold, int nOctaves, int nOctaveLayers, boolean extended, boolean upright)`
`protected void`	`finalize()`
`boolean`	`getExtended()`
`double`	`getHessianThreshold()`
`int`	`getNOctaveLayers()`
`int`	`getNOctaves()`
`boolean`	`getUpright()`
`void`	`setExtended(boolean extended)`
`void`	`setHessianThreshold(double hessianThreshold)`
`void`	`setNOctaveLayers(int nOctaveLayers)`
`void`	`setNOctaves(int nOctaves)`
`void`	`setUpright(boolean upright)`

Methods inherited from class org.opencv.features2d.Feature2D
compute, compute, defaultNorm, descriptorSize, descriptorType, detect, detect, detect, detect, detectAndCompute, detectAndCompute, empty, getDefaultName, read, write

Methods inherited from class org.opencv.core.Algorithm
clear, getNativeObjAddr, save

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

- Constructor Detail
  - SURF
```
protected SURF(long addr)
```
- Method Detail
  - __fromPtr__
```
public static SURF __fromPtr__(long addr)
```
  - create
```
public static SURF create(double hessianThreshold,
                          int nOctaves,
                          int nOctaveLayers,
                          boolean extended,
                          boolean upright)
```
    Parameters:
    
    hessianThreshold - Threshold for hessian keypoint detector used in SURF.
    
    nOctaves - Number of pyramid octaves the keypoint detector will use.
    
    nOctaveLayers - Number of octave layers within each octave.
    
    extended - Extended descriptor flag (true - use extended 128-element descriptors; false - use 64-element descriptors).
    
    upright - Up-right or rotated features flag (true - do not compute orientation of features; false - compute orientation).
    
    Returns:
    
    automatically generated
  - create
```
public static SURF create(double hessianThreshold,
                          int nOctaves,
                          int nOctaveLayers,
                          boolean extended)
```
    Parameters:
    
    hessianThreshold - Threshold for hessian keypoint detector used in SURF.
    
    nOctaves - Number of pyramid octaves the keypoint detector will use.
    
    nOctaveLayers - Number of octave layers within each octave.
    
    extended - Extended descriptor flag (true - use extended 128-element descriptors; false - use 64-element descriptors). false - compute orientation).
    
    Returns:
    
    automatically generated
  - create
```
public static SURF create(double hessianThreshold,
                          int nOctaves,
                          int nOctaveLayers)
```
    Parameters:
    
    hessianThreshold - Threshold for hessian keypoint detector used in SURF.
    
    nOctaves - Number of pyramid octaves the keypoint detector will use.
    
    nOctaveLayers - Number of octave layers within each octave. 64-element descriptors). false - compute orientation).
    
    Returns:
    
    automatically generated
  - create
```
public static SURF create(double hessianThreshold,
                          int nOctaves)
```
    Parameters:
    
    hessianThreshold - Threshold for hessian keypoint detector used in SURF.
    
    nOctaves - Number of pyramid octaves the keypoint detector will use. 64-element descriptors). false - compute orientation).
    
    Returns:
    
    automatically generated
  - create
```
public static SURF create(double hessianThreshold)
```
    Parameters:
    
    hessianThreshold - Threshold for hessian keypoint detector used in SURF. 64-element descriptors). false - compute orientation).
    
    Returns:
    
    automatically generated
  - create
```
public static SURF create()
```
    64-element descriptors). false - compute orientation).
    
    Returns:
    
    automatically generated
  - getExtended
```
public boolean getExtended()
```
  - getUpright
```
public boolean getUpright()
```
  - getHessianThreshold
```
public double getHessianThreshold()
```
  - getNOctaveLayers
```
public int getNOctaveLayers()
```
  - getNOctaves
```
public int getNOctaves()
```
  - setExtended
```
public void setExtended(boolean extended)
```
  - setHessianThreshold
```
public void setHessianThreshold(double hessianThreshold)
```
  - setNOctaveLayers
```
public void setNOctaveLayers(int nOctaveLayers)
```
  - setNOctaves
```
public void setNOctaves(int nOctaves)
```
  - setUpright
```
public void setUpright(boolean upright)
```
  - finalize
```
protected void finalize()
                 throws Throwable
```
    Overrides:
    
    finalize in class Feature2D
    
    Throws:
    
    Throwable

Class SURF

Field Summary

Fields inherited from class org.opencv.core.Algorithm

Constructor Summary

Method Summary

Methods inherited from class org.opencv.features2d.Feature2D

Methods inherited from class org.opencv.core.Algorithm

Methods inherited from class java.lang.Object

Constructor Detail

SURF

Method Detail

__fromPtr__

create

create

create

create

create

create

getExtended

getUpright

getHessianThreshold

getNOctaveLayers

getNOctaves

setExtended

setHessianThreshold

setNOctaveLayers

setNOctaves

setUpright

finalize

fromPtr