#include <visp3/core/vpMomentGravityCenter.h>

Inheritance diagram for vpMomentGravityCenter:

Public Member Functions
	vpMomentGravityCenter ()

virtual	~vpMomentGravityCenter ()

Inherited functionalities from vpMomentGravityCenter
void	compute ()

const std::vector< double > &	get () const

double	getXg () const

double	getYg () const

const char *	name () const

void	printDependencies (std::ostream &os) const

Inherited functionalities from vpMoment
const vpMomentObject &	getObject () const

void	linkTo (vpMomentDatabase &moments)

void	update (vpMomentObject &object)

Protected Member Functions
vpMomentDatabase &	getMoments () const

Protected Attributes
std::vector< double >	values

Friends
VISP_EXPORT std::ostream &	operator<< (std::ostream &os, const vpMomentGravityCenter &v)

Detailed Description

Class describing 2D gravity center moment.

This moment can be computed from scratch (no need to compute any different moments before computing this). It gives access to both coordinates of the gravity center $x_g$ and $y_g$ .

These coordinates are defined as follows: $x_g = \frac{m_{01}}{m_{00}}$ , $y_g = \frac{m_{10}}{m_{00}}$

#include <visp3/core/vpMomentObject.h>
#include <visp3/core/vpPoint.h>
#include <visp3/core/vpMomentGravityCenter.h>
#include <iostream>
int main()
{
  // Define the contour of an object by a 5 clockwise vertices on a plane
  vpPoint p;
  std::vector<vpPoint> vec_p; // vector that contains the vertices of the contour polygon
  p.set_x(-0.2); p.set_y(0.1); // coordinates in meters in the image plane (vertex 1)
  vec_p.push_back(p);
  p.set_x(+0.3); p.set_y(0.1); // coordinates in meters in the image plane (vertex 2)
  vec_p.push_back(p);
  p.set_x(+0.2); p.set_y(-0.1); // coordinates in meters in the image plane (vertex 3)
  vec_p.push_back(p);
  p.set_x(-0.2); p.set_y(-0.15); // coordinates in meters in the image plane (vertex 4)
  vec_p.push_back(p);
  p.set_x(-0.2); p.set_y(0.1); // close the contour (vertex 5 = vertex 1)
  vec_p.push_back(p);
  vpMomentObject obj(1); // Create an image moment object with 1 as
                         // maximum order (because only m00,m01,m10
                         // are needed to compute the gravity center primitive.
  obj.setType(vpMomentObject::DENSE_POLYGON); // The object is defined by a countour polygon
  obj.fromVector(vec_p); // Init the dense object with the polygon
  vpMomentGravityCenter g; // declaration of gravity center
  g.update(obj); // specify the object
  g.compute(); // compute the moment
  std::cout << "Xg=" << g.getXg() << std::endl; // access to Xg
  std::cout << "Yg=" << g.getYg() << std::endl; // access to Yg
  std::cout << g << std:: endl; // print gravity center
  return 0;
}

This example produces the following results:

Xg=0.0166667
Yg=-0.00833333
Xg=0.0166667, Yg=-0.00833333

Examples:: mbot-apriltag-ibvs.cpp, servoBebop2.cpp, and testMomentAlpha.cpp.

Definition at line 113 of file vpMomentGravityCenter.h.

Constructor & Destructor Documentation

◆ vpMomentGravityCenter()

vpMomentGravityCenter::vpMomentGravityCenter ( )

Default constructor.

Definition at line 54 of file vpMomentGravityCenter.cpp.

References vpMoment::values.

◆ ~vpMomentGravityCenter()

virtual vpMomentGravityCenter::~vpMomentGravityCenter ( )

inlinevirtual

Definition at line 117 of file vpMomentGravityCenter.h.

References vpMoment::compute().

Member Function Documentation

◆ compute()

void vpMomentGravityCenter::compute ( )

virtual

Computes the two gravity center coordinates commonly called $x_g$ and $y_g$ .

Implements vpMoment.

Reimplemented in vpMomentGravityCenterNormalized.

Examples:: mbot-apriltag-ibvs.cpp, servoBebop2.cpp, and testMomentAlpha.cpp.

Definition at line 45 of file vpMomentGravityCenter.cpp.

References vpMomentObject::get(), vpMoment::getObject(), and vpMoment::values.

Referenced by vpMomentCommon::getAlpha(), vpMomentCommon::getMu3(), vpMomentCommon::getSurface(), vpMomentCommon::updateAll(), and vpMomentGravityCenterNormalized::~vpMomentGravityCenterNormalized().

◆ get()

const std::vector< double > & vpMomentGravityCenter::get ( ) const

Returns a vector of the two gravity center coordinates.

Returns: Coordinates in the following moment: .

Definition at line 60 of file vpMomentGravityCenter.cpp.

References vpMoment::values.

Referenced by vpMomentGravityCenterNormalized::compute(), vpMomentCentered::compute(), vpFeatureMomentCentered::compute_interaction(), and vpMomentGravityCenterNormalized::printDependencies().

◆ getMoments()

vpMomentDatabase& vpMoment::getMoments ( ) const

inlineprotectedinherited

Returns the linked moment database.

Returns: the moment database

Definition at line 123 of file vpMoment.h.

Referenced by vpMomentArea::compute(), vpMomentGravityCenterNormalized::compute(), vpMomentCentered::compute(), vpMomentAreaNormalized::compute(), vpMomentCInvariant::compute(), vpMomentAlpha::compute(), vpMomentArea::printDependencies(), vpMomentGravityCenterNormalized::printDependencies(), vpMomentCentered::printDependencies(), vpMomentAreaNormalized::printDependencies(), and vpMomentAlpha::printDependencies().

◆ getObject()

const vpMomentObject& vpMoment::getObject ( ) const

inlineinherited

Definition at line 150 of file vpMoment.h.

◆ getXg()

double vpMomentGravityCenter::getXg ( ) const

inline

Shortcut function to retrieve $x_g$ .

Returns: The first gravity center coordinate.

Definition at line 127 of file vpMomentGravityCenter.h.

Referenced by vpFeatureMomentArea::compute_interaction(), vpFeatureMomentCentered::compute_interaction(), vpFeatureMomentAlpha::compute_interaction(), vpFeatureMomentAreaNormalized::compute_interaction(), vpFeatureMomentGravityCenter::compute_interaction(), vpFeatureMomentGravityCenterNormalized::compute_interaction(), and vpMomentCentered::printDependencies().

◆ getYg()

double vpMomentGravityCenter::getYg ( ) const

inline

Shortcut function to retrieve $y_g$ .

Returns: The second gravity center coordinate.

Definition at line 132 of file vpMomentGravityCenter.h.

Referenced by vpFeatureMomentArea::compute_interaction(), vpFeatureMomentCentered::compute_interaction(), vpFeatureMomentAlpha::compute_interaction(), vpFeatureMomentAreaNormalized::compute_interaction(), vpFeatureMomentGravityCenter::compute_interaction(), vpFeatureMomentGravityCenterNormalized::compute_interaction(), and vpMomentCentered::printDependencies().

◆ linkTo()

void vpMoment::linkTo ( vpMomentDatabase & data_base )

inherited

Links the moment to a database of moment primitives. If the moment depends on other moments, these moments must be linked to the same database.

Attention: Two moments of the same class cannot be stored in the same database
#include <visp3/core/vpMomentCentered.h>
#include <visp3/core/vpMomentDatabase.h>
#include <visp3/core/vpMomentGravityCenter.h>
#include <visp3/core/vpMomentObject.h>
#include <visp3/core/vpPoint.h>
int main()
{
vpPoint p;
std::vector<vpPoint> vec_p;
p.set_x(1); p.set_y(1); // coordinates in meters in the image plane (vertex 1)
vec_p.push_back(p); p.set_x(2); p.set_y(2); // coordinates in meters in the image plane (vertex 2)
vpMomentObject obj(2);
obj.setType(vpMomentObject::DISCRETE); // Discrete mode.
obj.fromVector(vec_p); // Init the dense object with the polygon
vpMomentDatabase db;
vpMomentGravityCenter G; // declaration of gravity center
vpMomentCentered mc; // mc contains centered moments
G.linkTo(db); //add gravity center to database
mc.linkTo(db); //centered moments depend on gravity, add them to the
//database to grant access
G.update(obj); // specify the object for gravity center
mc.update(obj); // and for centered moments
G.compute(); // compute the moment
mc.compute(); //compute centered moments AFTER gravity center
return 0;
}