Public Member Functions | Static Public Member Functions | Public Attributes | List of all members
cv::KeyPoint Class Reference

The Keypoint Class. More...

#include <features2d.hpp>

Public Member Functions

CV_WRAP KeyPoint ()
 the default constructor More...
 
 KeyPoint (Point2f _pt, float _size, float _angle=-1, float _response=0, int _octave=0, int _class_id=-1)
 the full constructor More...
 
CV_WRAP KeyPoint (float x, float y, float _size, float _angle=-1, float _response=0, int _octave=0, int _class_id=-1)
 another form of the full constructor More...
 
size_t hash () const
 

Static Public Member Functions

static void convert (const vector< KeyPoint > &keypoints, CV_OUT vector< Point2f > &points2f, const vector< int > &keypointIndexes=vector< int >())
 converts vector of keypoints to vector of points More...
 
static void convert (const vector< Point2f > &points2f, CV_OUT vector< KeyPoint > &keypoints, float size=1, float response=1, int octave=0, int class_id=-1)
 converts vector of points to the vector of keypoints, where each keypoint is assigned the same size and the same orientation More...
 
static float overlap (const KeyPoint &kp1, const KeyPoint &kp2)
 

Public Attributes

CV_PROP_RW Point2f pt
 coordinates of the keypoints More...
 
CV_PROP_RW float size
 diameter of the meaningful keypoint neighborhood More...
 
CV_PROP_RW float angle
 
CV_PROP_RW float response
 the response by which the most strong keypoints have been selected. More...
 
CV_PROP_RW int octave
 octave (pyramid layer) from which the keypoint has been extracted More...
 
CV_PROP_RW int class_id
 object class (if the keypoints need to be clustered by an object they belong to) More...
 

Detailed Description

The Keypoint Class.

The class instance stores a keypoint, i.e. a point feature found by one of many available keypoint detectors, such as Harris corner detector, cv::FAST, cv::StarDetector, cv::SURF, cv::SIFT, cv::LDetector etc.

The keypoint is characterized by the 2D position, scale (proportional to the diameter of the neighborhood that needs to be taken into account), orientation and some other parameters. The keypoint neighborhood is then analyzed by another algorithm that builds a descriptor (usually represented as a feature vector). The keypoints representing the same object in different images can then be matched using cv::KDTree or another method.

Constructor & Destructor Documentation

CV_WRAP cv::KeyPoint::KeyPoint ( )

the default constructor

cv::KeyPoint::KeyPoint ( Point2f  _pt,
float  _size,
float  _angle = -1,
float  _response = 0,
int  _octave = 0,
int  _class_id = -1 
)

the full constructor

CV_WRAP cv::KeyPoint::KeyPoint ( float  x,
float  y,
float  _size,
float  _angle = -1,
float  _response = 0,
int  _octave = 0,
int  _class_id = -1 
)

another form of the full constructor

Member Function Documentation

size_t cv::KeyPoint::hash ( ) const
static void cv::KeyPoint::convert ( const vector< KeyPoint > &  keypoints,
CV_OUT vector< Point2f > &  points2f,
const vector< int > &  keypointIndexes = vector< int >() 
)
static

converts vector of keypoints to vector of points

static void cv::KeyPoint::convert ( const vector< Point2f > &  points2f,
CV_OUT vector< KeyPoint > &  keypoints,
float  size = 1,
float  response = 1,
int  octave = 0,
int  class_id = -1 
)
static

converts vector of points to the vector of keypoints, where each keypoint is assigned the same size and the same orientation

static float cv::KeyPoint::overlap ( const KeyPoint kp1,
const KeyPoint kp2 
)
static

computes overlap for pair of keypoints; overlap is a ratio between area of keypoint regions intersection and area of keypoint regions union (now keypoint region is circle)

Member Data Documentation

CV_PROP_RW Point2f cv::KeyPoint::pt

coordinates of the keypoints

CV_PROP_RW float cv::KeyPoint::size

diameter of the meaningful keypoint neighborhood

CV_PROP_RW float cv::KeyPoint::angle

computed orientation of the keypoint (-1 if not applicable); it's in [0,360) degrees and measured relative to image coordinate system, ie in clockwise.

CV_PROP_RW float cv::KeyPoint::response

the response by which the most strong keypoints have been selected.

Can be used for the further sorting or subsampling

CV_PROP_RW int cv::KeyPoint::octave

octave (pyramid layer) from which the keypoint has been extracted

CV_PROP_RW int cv::KeyPoint::class_id

object class (if the keypoints need to be clustered by an object they belong to)


The documentation for this class was generated from the following file: