Visual Servoing Platform  version 3.6.1 under development (2024-05-27)
vpMomentCInvariant Class Reference

#include <visp3/core/vpMomentCInvariant.h>

+ Inheritance diagram for vpMomentCInvariant:

Public Member Functions

 vpMomentCInvariant (bool flg_sxsynormalization=false)
 
double C1 () const
 
double C2 () const
 
double C3 () const
 
double C4 () const
 
double C5 () const
 
double C6 () const
 
double C7 () const
 
double C8 () const
 
double C9 () const
 
double C10 () const
 
void compute ()
 
double get (unsigned int i) const
 
double getC (unsigned int i) const
 
double getI (unsigned int index) const
 
void printInvariants (std::ostream &os) const
 
double getII (unsigned int i) const
 
double getK () const
 
double getS (unsigned int i) const
 
const std::string name () const
 
void printI (unsigned int index)
 
double Px ()
 
double Py ()
 
double Sx () const
 
double Sy () const
 
double getIn1 () const
 
double getCN (unsigned int i) const
 
double getSN (unsigned int i) const
 
bool isSxSyfromNormalizedMoments () const
 
const std::vector< double > & getMomentVector () const
 
Inherited functionalities from vpMoment
const vpMomentObjectgetObject () const
 
const std::vector< double > & get () const
 
void linkTo (vpMomentDatabase &moments)
 
virtual void printDependencies (std::ostream &os) const
 
void update (vpMomentObject &object)
 

Protected Member Functions

vpMomentDatabasegetMoments () const
 

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 [6], [46].

The descriptions for the invariants $C_1$ to $C_{10}$ can be found in [6] and for invariants $P_x$, $P_y$, $S_x$, $S_y$ in [46].

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 <iostream>
#include <visp3/core/vpMomentCInvariant.h>
#include <visp3/core/vpMomentCommon.h>
#include <visp3/core/vpMomentObject.h>
#include <visp3/core/vpPoint.h>
int main()
{
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
bool success;
db.updateAll(obj); // Update AND compute all moments
//get C-invariant
= static_cast<const 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;
}
double get(unsigned int i) const
This class initializes and allows access to commonly used moments.
static std::vector< double > getMu3(vpMomentObject &object)
static double getAlpha(vpMomentObject &object)
static double getSurface(vpMomentObject &object)
Class for generic objects.
Class that defines a 3D point in the object frame and allows forward projection of a 3D point in the ...
Definition: vpPoint.h:77
void set_x(double x)
Set the point x coordinate in the image plane.
Definition: vpPoint.cpp:504
void set_y(double y)
Set the point y coordinate in the image plane.
Definition: vpPoint.cpp:506

vpMomentCInvariant depends on vpMomentCentered (see vpMomentDatabase and vpMomentCommon).

Definition at line 122 of file vpMomentCInvariant.h.

Constructor & Destructor Documentation

◆ vpMomentCInvariant()

vpMomentCInvariant::vpMomentCInvariant ( bool  flg_sxsynormalization = false)
explicit

Default constructor. (option to use a different calculation mode for sx and sy)

Definition at line 48 of file vpMomentCInvariant.cpp.

References vpMoment::values.

Member Function Documentation

◆ C1()

double vpMomentCInvariant::C1 ( ) const
inline

Shorcut for getting the value of $C_1$.

Definition at line 147 of file vpMomentCInvariant.h.

◆ C10()

double vpMomentCInvariant::C10 ( ) const
inline

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

Definition at line 183 of file vpMomentCInvariant.h.

◆ C2()

double vpMomentCInvariant::C2 ( ) const
inline

Shorcut for getting the value of $C_2$.

Definition at line 151 of file vpMomentCInvariant.h.

◆ C3()

double vpMomentCInvariant::C3 ( ) const
inline

Shorcut for getting the value of $C_3$.

Definition at line 155 of file vpMomentCInvariant.h.

◆ C4()

double vpMomentCInvariant::C4 ( ) const
inline

Shorcut for getting the value of $C_4$.

Definition at line 159 of file vpMomentCInvariant.h.

◆ C5()

double vpMomentCInvariant::C5 ( ) const
inline

Shorcut for getting the value of $C_5$.

Definition at line 163 of file vpMomentCInvariant.h.

◆ C6()

double vpMomentCInvariant::C6 ( ) const
inline

Shorcut for getting the value of $C_6$.

Definition at line 167 of file vpMomentCInvariant.h.

◆ C7()

double vpMomentCInvariant::C7 ( ) const
inline

Shorcut for getting the value of $C_7$.

Definition at line 171 of file vpMomentCInvariant.h.

◆ C8()

double vpMomentCInvariant::C8 ( ) const
inline

Shorcut for getting the value of $C_8$.

Definition at line 175 of file vpMomentCInvariant.h.

◆ C9()

double vpMomentCInvariant::C9 ( ) const
inline

Shorcut for getting the value of $C_9$.

Definition at line 179 of file vpMomentCInvariant.h.

◆ compute()

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 195 of file vpMomentCInvariant.cpp.

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

Referenced by vpMomentCommon::updateAll().

◆ get() [1/2]

◆ get() [2/2]

double vpMomentCInvariant::get ( unsigned int  i) const
inline

Gets the desired invariant.

Parameters
igiven index. For invariants from C1 to C10 the corresponding index is from 0 to 9. For $S_x$, $S_y$ the indexes are 10,11 and for $P_x$, $P_y$ they are 12,13.

Definition at line 193 of file vpMomentCInvariant.h.

◆ getC()

double vpMomentCInvariant::getC ( unsigned int  i) const
inline

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

Definition at line 198 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

◆ getCN()

double vpMomentCInvariant::getCN ( unsigned int  i) const
inline

Getter for c (calculated from normalized 2nd and 3ord order moments)

Definition at line 261 of file vpMomentCInvariant.h.

◆ getI()

double vpMomentCInvariant::getI ( unsigned int  index) const
inline

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

Definition at line 202 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

◆ getII()

double vpMomentCInvariant::getII ( unsigned int  i) const
inline

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

Definition at line 212 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

◆ getIn1()

double vpMomentCInvariant::getIn1 ( ) const
inline

Getters for I (calculated from normalized 2nd and 3ord order moments)

Definition at line 255 of file vpMomentCInvariant.h.

◆ getK()

double vpMomentCInvariant::getK ( ) const
inline

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

Definition at line 216 of file vpMomentCInvariant.h.

◆ getMoments()

◆ getMomentVector()

const std::vector<double>& vpMomentCInvariant::getMomentVector ( ) const
inline

To get all the invariant values as a whole.

Definition at line 277 of file vpMomentCInvariant.h.

References vpMoment::values.

◆ getObject()

◆ getS()

double vpMomentCInvariant::getS ( unsigned int  i) const
inline

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

Definition at line 221 of file vpMomentCInvariant.h.

Referenced by vpFeatureMomentCInvariant::compute_interaction().

◆ getSN()

double vpMomentCInvariant::getSN ( unsigned int  i) const
inline

Getter for s (calculated from normalized 2nd and 3ord order moments)

Definition at line 267 of file vpMomentCInvariant.h.

◆ isSxSyfromNormalizedMoments()

bool vpMomentCInvariant::isSxSyfromNormalizedMoments ( ) const
inline

To know if Sx and Sy were calculated from normalized moments or not

Definition at line 272 of file vpMomentCInvariant.h.

◆ 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()
{
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);
obj.setType(vpMomentObject::DISCRETE); // Discrete mode.
obj.fromVector(vec_p); // Init the dense object with the polygon
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;
}
This class defines the double-indexed centered moment descriptor .
This class allows to register all vpMoments so they can access each other according to their dependen...
Class describing 2D gravity center moment.
void linkTo(vpMomentDatabase &moments)
Definition: vpMoment.cpp:95
void update(vpMomentObject &object)
Definition: vpMoment.cpp:108
Parameters
data_base: database of moment primitives.
Examples
mbot-apriltag-ibvs.cpp, servoBebop2.cpp, servoPixhawkDroneIBVS.cpp, and testMomentAlpha.cpp.

Definition at line 95 of file vpMoment.cpp.

References vpMoment::name().

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

◆ name()

const std::string vpMomentCInvariant::name ( ) const
inlinevirtual

Moment name.

Implements vpMoment.

Definition at line 226 of file vpMomentCInvariant.h.

◆ printDependencies()

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

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 128 of file vpMoment.cpp.

◆ printI()

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 269 of file vpMomentCInvariant.cpp.

◆ printInvariants()

void vpMomentCInvariant::printInvariants ( std::ostream &  os) const

Print the moment invariants used to obtain the actual visual features

Print out all invariants that were computed There are 15 of them, as in [Point-based and region based.ITRO05] [46]

Definition at line 276 of file vpMomentCInvariant.cpp.

◆ Px()

double vpMomentCInvariant::Px ( )
inline

Shorcut for getting the value of $P_x$.

Definition at line 236 of file vpMomentCInvariant.h.

◆ Py()

double vpMomentCInvariant::Py ( )
inline

Shorcut for getting the value of $P_y$.

Definition at line 240 of file vpMomentCInvariant.h.

◆ Sx()

double vpMomentCInvariant::Sx ( ) const
inline

Shorcut for getting the value of $S_x$.

Definition at line 245 of file vpMomentCInvariant.h.

◆ Sy()

double vpMomentCInvariant::Sy ( ) const
inline

Shorcut for getting the value of $S_y$.

Definition at line 249 of file vpMomentCInvariant.h.

◆ update()

void vpMoment::update ( vpMomentObject moment_object)
inherited

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 108 of file vpMoment.cpp.

Friends And Related Function Documentation

◆ operator<<

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

Outputs the moment's values to a stream.

Definition at line 288 of file vpMomentCInvariant.cpp.

Member Data Documentation

◆ values