#include <vpMomentCInvariant.h>

Inheritance diagram for vpMomentCInvariant:

Public Member Functions
	vpMomentCInvariant ()

double	C1 ()

double	C2 ()

double	C3 ()

double	C4 ()

double	C5 ()

double	C6 ()

double	C7 ()

double	C8 ()

double	C9 ()

double	C10 ()

void	compute ()

double	get (unsigned int i)

double	getC (unsigned int i)

double	getI (unsigned int index)

double	getII (unsigned int i)

double	getK ()

double	getS (unsigned int i)

const char *	name ()

void	printI (unsigned int index)

double	Px ()

double	Py ()

double	Sx ()

double	Sy ()

vpMomentObject &	getObject ()

std::vector< double > &	get ()

void	linkTo (vpMomentDatabase &moments)

void	update (vpMomentObject &object)

Protected Member Functions
vpMomentDatabase &	getMoments ()

Protected Attributes
std::vector< double >	values

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

Detailed Description

This class defines several 2D (translation+rotation+scale) invariants for both symmetric and non-symmetric objects. These moment-based invariants are described in the following papers:

[1] "Point-based and region-based image moments for visual servoing of planar objects" by Omar Tahri and François Chaumette
[2] "Image moments: a general and useful set of features for visual servoing" by François Chaumette

The descriptions for the invariants $C_1$ to $C_{10}$ can be found in [1] and for invariants $P_x$ , $P_y$ , $S_x$ , $S_y$ in [2].

These invariants are classicaly used in visual servoing to control the out-of-plane rotations. The C-type or P-type invariants are used for non-symmetric objects whereas the S-type invariants are used for symmetric objects.

For most cases of non-symmetric objects, ( $C_4$ , $C_6$ ) or ( $P_x$ , $P_y$ ) couples are widely used to control x and y rotations. For symmetric objects $S_x$ and $S_y$ are the only choice.

There are 14 translation+rotation+scale invariants (10 C-type, 2 P-type and 2 S-type) that can be accessed from by vpMomentCInvariant::get or any of the get shortcuts.

The example below shows how to retrieve the $C_2$ invariant:

#include <visp/vpMomentObject.h>
#include <visp/vpPoint.h>
#include <visp/vpMomentCInvariant.h>
#include <visp/vpMomentCommon.h>
#include <iostream>
int main()
{
  vpPoint p;
  std::vector<vpPoint> vec_p;
  p.set_x(6); 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(3); // coordinates in meters in the image plane (vertex 2)
  vec_p.push_back(p);
  p.set_x(0); p.set_y(1.2); // coordinates in meters in the image plane (vertex 1)
  vec_p.push_back(p);
  p.set_x(-7); p.set_y(-4); // coordinates in meters in the image plane (vertex 2)
  vec_p.push_back(p);
  vpMomentObject obj(5); // Create an image moment object with 5 as maximum order
  obj.setType(vpMomentObject::DISCRETE); // Discrete mode for object
  obj.fromVector(vec_p);
  //initialisation with default values
  vpMomentCommon db(vpMomentCommon::getSurface(obj),vpMomentCommon::getMu3(obj),vpMomentCommon::getAlpha(obj),1.);
  bool success;
  db.updateAll(obj); // Update AND compute all moments
  //get C-invariant
  vpMomentCInvariant& C = static_cast<vpMomentCInvariant&>(db.get("vpMomentCInvariant",success));
  if(success)
      std::cout << C.get(1) << std:: endl; // print C2 invariant
  else
      std::cout << "vpMomentCInvariant not found." << std::endl;
  return 0;
}

vpMomentCInvariant depends on vpMomentCentered (see vpMomentDatabase and vpMomentCommon).

Definition at line 120 of file vpMomentCInvariant.h.

Constructor & Destructor Documentation

vpMomentCInvariant::vpMomentCInvariant ( )

Default constructor.

Definition at line 49 of file vpMomentCInvariant.cpp.

References vpMoment::values.

Member Function Documentation

double vpMomentCInvariant::C1 ( )

inline

Shorcut for getting the value of $C_1$ .

Definition at line 136 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C10 ( )

inline

Shorcut for getting the value of $C_{10}$ .

Definition at line 172 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C2 ( )

inline

Shorcut for getting the value of $C_2$ .

Definition at line 140 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C3 ( )

inline

Shorcut for getting the value of $C_3$ .

Definition at line 144 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C4 ( )

inline

Shorcut for getting the value of $C_4$ .

Definition at line 148 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C5 ( )

inline

Shorcut for getting the value of $C_5$ .

Definition at line 152 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C6 ( )

inline

Shorcut for getting the value of $C_6$ .

Definition at line 156 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C7 ( )

inline

Shorcut for getting the value of $C_7$ .

Definition at line 160 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C8 ( )

inline

Shorcut for getting the value of $C_8$ .

Definition at line 164 of file vpMomentCInvariant.h.

double vpMomentCInvariant::C9 ( )

inline

Shorcut for getting the value of $C_9$ .

Definition at line 168 of file vpMomentCInvariant.h.

void vpMomentCInvariant::compute ( )

virtual

Computes translation-plane-rotation-scale invariants. Depends on vpMomentCentered. All possible invariants are computed here. The selection of the invariant is done afterwards.

Implements vpMoment.

Definition at line 162 of file vpMomentCInvariant.cpp.

References vpMomentObject::DISCRETE, vpMomentCentered::get(), vpMomentDatabase::get(), vpMomentObject::get(), vpMoment::getMoments(), vpMoment::getObject(), vpException::notInitialized, and vpMoment::values.

Referenced by vpMomentCommon::updateAll().

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

inlineinherited

Returns all values computed by the moment.

Returns: vector of values

Definition at line 125 of file vpMoment.h.

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

double vpMomentCInvariant::get ( unsigned int i )

inline

Gets the desired invariant.

Parameters

i	given index. For invariants from C1 to C10 the corresponding index is from 0 to 9. For , the indexes are 10,11 and for , they are 12,13.

Definition at line 180 of file vpMomentCInvariant.h.

double vpMomentCInvariant::getC ( unsigned int i )

inline

Access to partial invariant c (see [2]).

Definition at line 185 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

double vpMomentCInvariant::getI ( unsigned int index )

inline

Access to partial invariants. The index convention is the same as in [1].

Definition at line 189 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

double vpMomentCInvariant::getII ( unsigned int i )

inline

Access to partial invariant I (see [2]).

Definition at line 194 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

double vpMomentCInvariant::getK ( )

inline

Access to partial invariant K (see [2]).

Definition at line 198 of file vpMomentCInvariant.h.

vpMomentDatabase& vpMoment::getMoments ( )

inlineprotectedinherited

Returns the linked moment database.

Returns: the moment database

Definition at line 115 of file vpMoment.h.

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

vpMomentObject& vpMoment::getObject ( )

inlineinherited

Definition at line 119 of file vpMoment.h.

double vpMomentCInvariant::getS ( unsigned int i )

inline

Access to partial invariant S (see [2]).

Definition at line 203 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

void vpMoment::linkTo ( vpMomentDatabase & moments )

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 <visp/vpMomentObject.h>

#include <visp/vpPoint.h>

#include <visp/vpMomentGravityCenter.h>

#include <visp/vpMomentDatabase.h>

#include <visp/vpMomentCentered.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 containts 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

moments : database of moment primitives.

Definition at line 104 of file vpMoment.cpp.

References vpMoment::name().

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

const char* vpMomentCInvariant::name ( )

inlinevirtual

Moment name.

Implements vpMoment.

Definition at line 208 of file vpMomentCInvariant.h.

void vpMomentCInvariant::printI ( unsigned int index )

Print partial invariant.

Prints the temporary invariants. Used for debug purposes only

Parameters

index : index of the temporary invariant

Definition at line 209 of file vpMomentCInvariant.cpp.

double vpMomentCInvariant::Px ( )

inline

Shorcut for getting the value of $P_x$ .

Definition at line 218 of file vpMomentCInvariant.h.

double vpMomentCInvariant::Py ( )

inline

Shorcut for getting the value of $P_y$ .

Definition at line 222 of file vpMomentCInvariant.h.

double vpMomentCInvariant::Sx ( )

inline

Shorcut for getting the value of $S_x$ .

Definition at line 227 of file vpMomentCInvariant.h.

double vpMomentCInvariant::Sy ( )

inline

Shorcut for getting the value of $S_y$ .

Definition at line 231 of file vpMomentCInvariant.h.

void vpMoment::update ( vpMomentObject & object )

inherited

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

Parameters

object : object descriptor of the current camera vision.

Definition at line 117 of file vpMoment.cpp.

Friends And Related Function Documentation

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

friend

Outputs the moment's values to a stream.

Definition at line 216 of file vpMomentCInvariant.cpp.

Member Data Documentation

std::vector<double> vpMoment::values

protectedinherited

Definition at line 110 of file vpMoment.h.

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

Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation