vpMoment Class Reference

#include <visp3/core/vpMoment.h>

Inheritance diagram for vpMoment:

Public Member Functions
	vpMoment ()
virtual	~vpMoment ()

Protected Member Functions
vpMomentDatabase &	getMoments () const

Protected Attributes
std::vector< double >	values

Inherited functionalities from vpMoment
virtual void	compute ()=0
const vpMomentObject &	getObject () const
const std::vector< double > &	get () const
void	linkTo (vpMomentDatabase &moments)
virtual const std::string	name () const =0
virtual void	printDependencies (std::ostream &os) const
void	update (vpMomentObject &object)
VISP_EXPORT std::ostream &	operator<< (std::ostream &os, const vpMoment &m)

Detailed Description

This class defines shared methods/attributes for 2D moments.

All moments or combination of moments in the moments module are based on this class. A moment uses a vpMomentObject object to access all useful information. Moment values are obtained by a 4-step process common for all moment types:

• Declaration.

  vpMoment moment;

• Update with object.

  moment.update(object);

• Compute the moment value

  moment.compute();

• Access the values:

  std::vector<double> values = moment.get();

A moment may also be linked to a vpMomentDatabase. Moments linked to a database are able to access each others values. Some moments can be computed only if they are linked to a a database containing their dependencies. Linking to a database is done using the vpMoment::linkTo(...) method.

There are no constraints about format of the array returned by vpMoment::get(); any implementation is fine.

Each moment must have a string name by implementing the char* vpMoment::name() method which allows to identify the moment in the database. Each moment must also implement a compute method describing how to obtain its values from the object.

Attention

Order of moment computation DOES matter: when you compute a moment using vpMoment::compute(), all moment dependencies must be computed. We recall that implemented moments are:

• vpMomentAlpha
• vpMomentArea
• vpMomentAreaNormalized
• vpMomentBasic
• vpMomentCentered
• vpMomentCInvariant
• vpMomentGravityCenter
• vpMomentGravityCenterNormalized

Definition at line 105 of file vpMoment.h.

Constructor & Destructor Documentation

vpMoment()

vpMoment::vpMoment

(

)

Default constructor

Definition at line 61 of file vpMoment.cpp.

~vpMoment()

virtual vpMoment::~vpMoment ( )

inlinevirtual

Virtual destructor.

Definition at line 140 of file vpMoment.h.

Member Function Documentation

compute()

virtual void vpMoment::compute ( )

pure virtual

Implemented in vpMomentGravityCenterNormalized, vpMomentGravityCenter, vpMomentCInvariant, vpMomentCentered, vpMomentBasic, vpMomentAreaNormalized, vpMomentArea, and vpMomentAlpha.

get()

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

inline

Returns all values computed by the moment.

Returns

vector of values

Definition at line 150 of file vpMoment.h.

Referenced by vpMomentGravityCenterNormalized::compute(), vpFeatureMomentArea::compute_interaction(), vpFeatureMomentAreaNormalized::compute_interaction(), vpFeatureMomentGravityCenterNormalized::compute_interaction(), vpMomentCentered::get(), vpFeatureMoment::init(), vpMomentGravityCenterNormalized::printDependencies(), and vpFeatureMoment::update().

getMoments()

vpMomentDatabase& vpMoment::getMoments ( ) const

inlineprotected

Returns the linked moment database.

Returns

the moment database

Definition at line 118 of file vpMoment.h.

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

getObject()

const vpMomentObject& vpMoment::getObject ( ) const

inline

Definition at line 145 of file vpMoment.h.

Referenced by vpMomentArea::compute(), vpMomentAreaNormalized::compute(), vpMomentCentered::compute(), vpMomentCInvariant::compute(), vpMomentGravityCenter::compute(), vpFeatureMomentAlpha::compute_interaction(), vpFeatureMomentArea::compute_interaction(), vpFeatureMomentAreaNormalized::compute_interaction(), vpFeatureMomentBasic::compute_interaction(), vpFeatureMomentCentered::compute_interaction(), vpFeatureMomentCInvariant::compute_interaction(), vpFeatureMomentGravityCenter::compute_interaction(), vpFeatureMomentGravityCenterNormalized::compute_interaction(), vpMomentBasic::get(), vpMomentCentered::get(), vpFeatureMomentBasic::interaction(), vpFeatureMomentCentered::interaction(), vpMomentArea::printDependencies(), vpMomentAreaNormalized::printDependencies(), vpMomentBasic::printDependencies(), vpMomentCentered::printDependencies(), vpMomentGravityCenter::printDependencies(), vpMomentCentered::printWithIndices(), and vpMomentCentered::set().

linkTo()

void vpMoment::linkTo

(

vpMomentDatabase &

data_base

)

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>
 
#ifdef ENABLE_VISP_NAMESPACE
using namespace VISP_NAMESPACE_NAME;
#endif
 
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)
  vec_p.push_back(p);
 
  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;
}

Parameters

data_base

: database of moment primitives.

Examples

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

Definition at line 114 of file vpMoment.cpp.

References name().

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

name()

virtual const std::string vpMoment::name ( ) const

pure virtual

Implemented in vpMomentGravityCenterNormalized, vpMomentGravityCenter, vpMomentCInvariant, vpMomentCentered, vpMomentBasic, vpMomentAreaNormalized, vpMomentArea, and vpMomentAlpha.

Referenced by linkTo().

printDependencies()

void vpMoment::printDependencies ( std::ostream &  os ) const

virtual

Prints values of all dependent moments required to calculate a specific vpMoment. Not made pure to maintain compatibility Recommended : Types inheriting from vpMoment should implement this function

Reimplemented in vpMomentGravityCenterNormalized, vpMomentGravityCenter, vpMomentCentered, vpMomentBasic, vpMomentAreaNormalized, vpMomentArea, and vpMomentAlpha.

Definition at line 134 of file vpMoment.cpp.

update()

void vpMoment::update

(

vpMomentObject &

moment_object

)

Updates the moment with the current object. This does not compute any values.

Parameters

moment_object

: object descriptor of the current camera vision.

Definition at line 127 of file vpMoment.cpp.

Friends And Related Function Documentation

operator<<

VISP_EXPORT std::ostream& operator<< ( std::ostream &  os, const vpMoment &  m  )

friend

Prints the moment contents to a stream

Parameters

os	: a std::stream.
m	: a moment instance.

Definition at line 50 of file vpMoment.cpp.

Member Data Documentation

values

std::vector<double> vpMoment::values

protected

Definition at line 113 of file vpMoment.h.

Referenced by vpMomentAlpha::compute(), vpMomentArea::compute(), vpMomentAreaNormalized::compute(), vpMomentCentered::compute(), vpMomentCInvariant::compute(), vpMomentGravityCenter::compute(), vpMomentGravityCenterNormalized::compute(), vpMomentGravityCenter::get(), vpMomentCentered::get(), vpMomentCInvariant::getMomentVector(), vpMomentCentered::set(), vpMomentAlpha::vpMomentAlpha(), vpMomentArea::vpMomentArea(), vpMomentAreaNormalized::vpMomentAreaNormalized(), vpMomentCInvariant::vpMomentCInvariant(), and vpMomentGravityCenter::vpMomentGravityCenter().