cv::KeyPoint Class Reference

#include <features2d.hpp>

Public Member Functions
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
	KeyPoint (Point2f _pt, float _size, float _angle=-1, float _response=0, int _octave=0, int _class_id=-1)
	the full constructor
CV_WRAP	KeyPoint ()
	the default constructor
Static Public Member Functions
static void	convert (const std::vector< Point2f > &points2f, CV_OUT std::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
static void	convert (const std::vector< KeyPoint > &keypoints, CV_OUT std::vector< Point2f > &points2f, const std::vector< int > &keypointIndexes=std::vector< int >())
	converts vector of keypoints to vector of points
static float	overlap (const KeyPoint &kp1, const KeyPoint &kp2)
Public Attributes
CV_PROP_RW float	angle
	computed orientation of the keypoint (-1 if not applicable)
CV_PROP_RW int	class_id
	object class (if the keypoints need to be clustered by an object they belong to)
CV_PROP_RW int	octave
	octave (pyramid layer) from which the keypoint has been extracted
CV_PROP_RW Point2f	pt
	coordinates of the keypoints
CV_PROP_RW float	response
	the response by which the most strong keypoints have been selected. Can be used for the further sorting or subsampling
CV_PROP_RW float	size
	diameter of the meaningfull keypoint neighborhood

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 ( ) [inline]

the default constructor

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

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`
	)			`[inline]`

another form of the full constructor

Member Function Documentation

static void cv::KeyPoint::convert	(	const std::vector< Point2f > &	points2f,
		CV_OUT std::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 void cv::KeyPoint::convert	(	const std::vector< KeyPoint > &	keypoints,
		CV_OUT std::vector< Point2f > &	points2f,
		const std::vector< int > &	keypointIndexes = `std::vector< int >()`
	)			`[static]`

converts vector of keypoints to vector of points

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)