libvisp-dev 2.8.0-4 / usr / include / visp / vpMomentAlpha.h

/****************************************************************************
 *
 * $Id: vpMomentAlpha.h 4056 2013-01-05 13:04:42Z fspindle $
 *
 * This file is part of the ViSP software.
 * Copyright (C) 2005 - 2013 by INRIA. All rights reserved.
 *
 * This software is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * ("GPL") version 2 as published by the Free Software Foundation.
 * See the file LICENSE.txt at the root directory of this source
 * distribution for additional information about the GNU GPL.
 *
 * For using ViSP with software that can not be combined with the GNU
 * GPL, please contact INRIA about acquiring a ViSP Professional
 * Edition License.
 *
 * See http://www.irisa.fr/lagadic/visp/visp.html for more information.
 *
 * This software was developed at:
 * INRIA Rennes - Bretagne Atlantique
 * Campus Universitaire de Beaulieu
 * 35042 Rennes Cedex
 * France
 * http://www.irisa.fr/lagadic
 *
 * If you have questions regarding the use of this file, please contact
 * INRIA at visp@inria.fr
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *
 * Description:
 * Alpha moment descriptor for in-plane orientation.
 *
 * Authors:
 * Filip Novotny
 *
 *****************************************************************************/

/*!
  \file vpMomentAlpha.h
  \brief Alpha moment descriptor for in-plane orientation.
*/

#ifndef __MOMENTALPHA_H__
#define __MOMENTALPHA_H__

#include <visp/vpMoment.h>

/*!
  \class vpMomentAlpha

  \ingroup TrackingMoments

  \brief This class defines the orientation of the object inside the plane parallel to the object.

  The value of the moment is computed in radians in a \f$ [-\pi/2 .. \pi/2] \f$ interval at most by the formula \f$ \alpha = \frac{1}{2} arctan(\frac{2\mu_{11}}{\mu_{20}-\mu_{02}}) \f$.

  To obtain the \f$ [-\pi .. \pi] \f$ precision, you have to specify reference information. This reference information
  describes an object with 0 rad orientation or at least an orientation between \f$ -\pi/2 \f$ and \f$ \pi/2 \f$ rad.
  The nature of this information are third-order centered moments and a reference value of alpha.
  Reference centered moments are obtained with vpMomentCentered and reference alpha is obtained with vpMomentAlpha using the reference constructor.

  Therefore there are two modes for vpMomentAlpha and one constructor per mode:
  - Reference mode (using the empty constructor):
  The vpMomentAlpha doesn't need any additionnal information, it will compute its values from a reference object.
  - Relative mode (using non-empty constructor):
  The vpMomentAlpha is computed relative a reference alpha.
  By knowing the reference, it may distinguish in-plane rotations of \f$ \alpha \f$ from rotations of \f$ \alpha + \pi \f$.

  The following code demonstrates a calculation of a reference alpha and then uses this alpha to estimate the orientation
  of the same object after performing a 180 degrees rotation.
  Therefore the first and second alpha should have opposite values.

  \code
#include <visp/vpMomentObject.h>
#include <visp/vpPoint.h>
#include <visp/vpMomentGravityCenter.h>
#include <visp/vpMomentDatabase.h>
#include <visp/vpMomentCentered.h>
#include <visp/vpMomentAlpha.h>
#include <iostream>
#include <vector>
#include <algorithm>

//generic function for printing
void print (double i) { std::cout << i << "\t";}

int main()
{
  vpPoint p;
  std::vector<vpPoint> vec_p; // vector that contains the vertices of the contour polygon

  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);
  p.set_x(-3); p.set_y(0); // coordinates in meters in the image plane (vertex 3)
  vec_p.push_back(p);
  p.set_x(-3); p.set_y(-1); // coordinates in meters in the image plane (vertex 4)
  vec_p.push_back(p);

  //////////////////////////////REFERENCE VALUES////////////////////////////////
  vpMomentObject objRef(3); // Reference object. Must be of order 3
                            // because we will need the 3rd order
                            // centered moments
  objRef.setType(vpMomentObject::DENSE_POLYGON); // object is the inner part of a polygon
  objRef.fromVector(vec_p); // Init the dense object with the polygon

  vpMomentDatabase dbRef; //reference database
  vpMomentGravityCenter gRef; // declaration of gravity center
  vpMomentCentered mcRef; //  centered moments
  vpMomentAlpha alphaRef; //declare alpha as reference

  gRef.linkTo(dbRef); //add gravity center to database
  mcRef.linkTo(dbRef); //add centered moments
  alphaRef.linkTo(dbRef); //add alpha depending on centered moments

  dbRef.updateAll(objRef); // All of the moments must be updated, not just alpha

  gRef.compute(); // compute the moment
  mcRef.compute(); //compute centered moments AFTER gravity center
  alphaRef.compute(); //compute alpha AFTER centered moments.

  //the order of values in the vector must be as follows:
  //mu30 mu21 mu12 mu03
  std::vector<double> mu3ref(4);
  mu3ref[0] = mcRef.get(3,0);
  mu3ref[1] = mcRef.get(2,1);
  mu3ref[2] = mcRef.get(1,2);
  mu3ref[3] = mcRef.get(0,3);


  std::cout << "--- Reference object ---" << std::endl;
  std::cout << "alphaRef=" << alphaRef << std::endl << "mu3="; // print reference alpha
  std::for_each (mu3ref.begin(), mu3ref.end(),print);
  std::cout << std::endl;

  ////////////CURRENT VALUES (same object rotated 180deg - must be
  ////////////entered in reverse order)////////////////
  vec_p.clear();

  p.set_x(-3); p.set_y(1); // coordinates in meters in the image plane (vertex 4)
  vec_p.push_back(p);
  p.set_x(-3); p.set_y(0); // coordinates in meters in the image plane (vertex 3)
  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);
  p.set_x(1); p.set_y(-1); // coordinates in meters in the image plane (vertex 1)
  vec_p.push_back(p);


  vpMomentObject obj(3); // second object. Order 3 is also required
                         // because of the Alpha will compare
                         // third-order centered moments to given reference.

  obj.setType(vpMomentObject::DENSE_POLYGON); // object is the inner part of a polygon
  obj.fromVector(vec_p); // Init the dense object with the polygon

  vpMomentDatabase db; // database
  vpMomentGravityCenter g; // declaration of gravity center
  vpMomentCentered mc; // mc containts centered moments
  vpMomentAlpha alpha(mu3ref,alphaRef.get()); //declare alpha as relative to a reference

  g.linkTo(db); //add gravity center to database
  mc.linkTo(db); //add centered moments
  alpha.linkTo(db); //add alpha depending on centered moments

  db.updateAll(obj); // All of the moments must be updated

  g.compute(); // compute the moment
  mc.compute(); //compute centered moments AFTER gravity center
  alpha.compute(); //compute alpha AFTER centered moments.

  std::cout << "--- current object ---" << std::endl;
  std::cout << "alpha=" << alpha.get() << std::endl;

  return 0;
}

  \endcode
This program outputs:
\code
--- Reference object ---
alphaRef=0.441601
mu3=1.80552	0.921882	0.385828	0.122449
--- current object ---
alpha=-0.441601

\endcode

Shortcuts for quickly getting those references exist in vpMomentCommon.

This moment depends on vpMomentCentered.
*/
class VISP_EXPORT vpMomentAlpha : public vpMoment {
 private:	
    bool isRef;
    bool symmetric;
    std::vector<double> ref;
    double alphaRef;
 public:	
	
        vpMomentAlpha();
        vpMomentAlpha(std::vector<double>& ref,double alphaRef);

        void compute();
        /*!
          Retrieve the orientation of the object as a single double value.
          */
        double get(){ return values[0]; }
        /*!
          Moment name.
          */
	const char* name(){return "vpMomentAlpha";}

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

};

#endif