exampleAlphaShape.cpp File Reference

#include <iostream>
#include "DGtal/base/Common.h"
#include "DGtal/base/IteratorCirculatorTraits.h"
#include "DGtal/helpers/StdDefs.h"
#include "DGtal/geometry/tools/Hull2DHelpers.h"
#include "DGtal/geometry/tools/PolarPointComparatorBy2x2DetComputer.h"
#include "DGtal/geometry/tools/determinant/AvnaimEtAl2x2DetSignComputer.h"
#include "DGtal/geometry/tools/determinant/InHalfPlaneBySimple3x3Matrix.h"
#include "DGtal/geometry/tools/determinant/InGeneralizedDiskOfGivenRadius.h"
#include "DGtal/shapes/ShapeFactory.h"
#include "DGtal/shapes/Shapes.h"
#include "DGtal/topology/DigitalSetBoundary.h"
#include "DGtal/topology/DigitalSurface.h"
#include "DGtal/graph/DepthFirstVisitor.h"
#include "DGtal/io/boards/Board2D.h"

Go to the source code of this file.

Functions
template<typename ForwardIterator , typename Board >
void	drawPolygon (const ForwardIterator &itb, const ForwardIterator &ite, Board &aBoard, bool isClosed=true)
void	alphaShape ()
int	main (int argc, char **argv)

Detailed Description

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Author

Tristan Roussillon (trist.nosp@m.an.r.nosp@m.oussi.nosp@m.llon.nosp@m.@liri.nosp@m.s.cn.nosp@m.rs.fr ) Laboratoire d'InfoRmatique en Image et Systèmes d'information - LIRIS (CNRS, UMR 5205), CNRS, France

Date

2013/12/17

An example file named exampleAlphaShape.

This file is part of the DGtal library.

Definition in file exampleAlphaShape.cpp.

Function Documentation

alphaShape()

void alphaShape

(

)

Algorithms that computes the alpha-shape of a point set

[Hull2D-RadiusPredicateInf]

[Hull2D-RadiusPredicateInf]

[Hull2D-ClosedGrahamScan]

[Hull2D-ClosedGrahamScan]

[Hull2D-RadiusPredicateM1]

[Hull2D-RadiusPredicateM1]

[Hull2D-RadiusPredicateMsqrt5]

[Hull2D-RadiusPredicateMsqrt5]

[Hull2D-RadiusPredicateM5]

[Hull2D-RadiusPredicateM5]

[Hull2D-RadiusPredicateP8]

[Hull2D-RadiusPredicateP8]

[Hull2D-RadiusPredicateP9]

[Hull2D-RadiusPredicateP9]

Examples

geometry/tools/exampleAlphaShape.cpp.

Definition at line 123 of file exampleAlphaShape.cpp.

{
 
  //Digitization of a disk of radius 8
  Ball2D<Z2i::Space> ball(Z2i::Point(0,0), 8);
  Z2i::Domain domain(ball.getLowerBound(), ball.getUpperBound());
  Z2i::DigitalSet digitalSet(domain);   
  Shapes<Z2i::Domain>::euclideanShaper(digitalSet, ball);
  
  //Contour of the digital set
  Z2i::KSpace kspace; 
  kspace.init(domain.lowerBound()-Z2i::Point(1,1), domain.upperBound()+Z2i::Point(1,1), true); 
  typedef DigitalSetBoundary<Z2i::KSpace, Z2i::DigitalSet> DigitalSurfaceContainer;
  typedef DigitalSurface<DigitalSurfaceContainer> CustomDigitalSurface; 
  DigitalSurfaceContainer digitalSurfaceContainer( kspace, digitalSet ); 
  CustomDigitalSurface digitalSurface( digitalSurfaceContainer ); 
 
  //Grid curve
  Z2i::Curve gridCurve; 
  typedef DepthFirstVisitor<DigitalSurface<DigitalSurfaceContainer> > CustomVisitor;
  CustomVisitor visitor( digitalSurface, *digitalSurface.begin() );
  while ( ! visitor.finished() )
    {
      gridCurve.pushBack( visitor.current().first );
      visitor.expand();
    }
 
  //Point set defined as the set of (not duplicated) inner points  
  typedef Z2i::Curve::InnerPointsRange PointRange; 
  PointRange pointsRange = gridCurve.getInnerPointsRange();
  vector<Z2i::Point> border; 
  unique_copy( pointsRange.begin(), pointsRange.end(), back_inserter( border ) ); 
 
  //namespace for hull functions
  using namespace functions::Hull2D; 
 
  { //alpha = 0
    trace.info() << " alpha == 0 " << endl; 
    vector<Z2i::Point> res; 
    
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(true, 1, 0); //alpha = 0; 1/alpha -> +inf 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
 
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShape0.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShape0.png", Board2D::CairoPNG);
#endif
 
   }
 
  { //alpha = 0
    trace.info() << " alpha == 0 " << endl; 
    vector<Z2i::Point> res; 
    
    //comparator and functor
    typedef InHalfPlaneBySimple3x3Matrix<Z2i::Point, DGtal::int64_t> Functor;  
    Functor functor; 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
    
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShape0bis.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShape0bis.png", Board2D::CairoPNG);
#endif
 
   }
 
  //negative alpha shape
  { //alpha = -1
    trace.info() << " alpha == -1 " << endl; 
    vector<Z2i::Point> res; 
 
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(false, 1, 1); //1/alpha = -sqrt(1/1) = -1 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
    
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShapeM1.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShapeM1.png", Board2D::CairoPNG);
#endif
 
   }
 
  { //alpha = -sqrt(5)
    trace.info() << " alpha == -sqrt(5) " << endl; 
    vector<Z2i::Point> res; 
 
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(false, 5, 1); //1/alpha = -sqrt(5) 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
    
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShapeMSqrt5.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShapeMSqrt5.png", Board2D::CairoPNG);
#endif
 
  }
 
  { //alpha = -5
    trace.info() << " alpha == -5 " << endl; 
    vector<Z2i::Point> res; 
 
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(false, 25, 1); //1/alpha = -sqrt(25/1) = -5 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
    
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShapeM5.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShapeM5.png", Board2D::CairoPNG);
#endif
 
  }
 
  //positive alpha shape
  { 
    trace.info() << " alpha == 8 " << endl; 
    vector<Z2i::Point> res; 
 
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(true, 64, 1); //1/alpha = sqrt(64/1) = 8 
    typedef PredicateFromOrientationFunctor2<Functor, false, true> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
 
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShapeP8.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShapeP8.png", Board2D::CairoPNG);
#endif
 
  }
 
  //positive alpha shape
  { 
    trace.info() << " alpha == 9 " << endl; 
    vector<Z2i::Point> res; 
 
    typedef AvnaimEtAl2x2DetSignComputer<DGtal::int64_t> DetComputer; 
    typedef InGeneralizedDiskOfGivenRadius<Z2i::Point, DetComputer> Functor; 
    Functor functor(true, 81, 1); //1/alpha = sqrt(81/1) = 9 
    typedef PredicateFromOrientationFunctor2<Functor> Predicate; 
    Predicate predicate( functor ); 
 
    closedGrahamScanFromAnyPoint( border.begin(), border.end(), back_inserter( res ), predicate );   
    
    //display
    Board2D board;
    drawPolygon( res.begin(), res.end(), board ); 
    board.saveSVG( "AlphaShapeP9.svg" );  
#ifdef WITH_CAIRO
    board.saveCairo("AlphaShapeP9.png", Board2D::CairoPNG);
#endif
 
  }
 
}

References domain, drawPolygon(), DGtal::Shapes< TDomain >::euclideanShaper(), DGtal::GridCurve< TKSpace >::getInnerPointsRange(), DGtal::Ball2D< TSpace >::getLowerBound(), DGtal::Ball2D< TSpace >::getUpperBound(), DGtal::Trace::info(), DGtal::KhalimskySpaceND< dim, TInteger >::init(), DGtal::HyperRectDomain< TSpace >::lowerBound(), DGtal::GridCurve< TKSpace >::pushBack(), LibBoard::Board::saveCairo(), LibBoard::Board::saveSVG(), DGtal::trace, and DGtal::HyperRectDomain< TSpace >::upperBound().

Referenced by main().

drawPolygon()

template<typename ForwardIterator , typename Board >

void drawPolygon	(	const ForwardIterator &	itb,
		const ForwardIterator &	ite,
		Board &	aBoard,
		bool	isClosed = true
	)

Examples

geometry/tools/exampleAlphaShape.cpp, and geometry/tools/exampleConvexHull2D.cpp.

Definition at line 79 of file exampleAlphaShape.cpp.

{
  BOOST_CONCEPT_ASSERT(( boost_concepts::ForwardTraversalConcept<ForwardIterator> )); 
  BOOST_CONCEPT_ASSERT(( boost_concepts::ReadableIteratorConcept<ForwardIterator> )); 
  typedef typename IteratorCirculatorTraits<ForwardIterator>::Value Point; 
 
  ForwardIterator it = itb; 
  if (it != ite)
    {//for the first point
      Point p1 = *it;
      Point p = p1; 
      //display
      aBoard << SetMode( p.className(), "Grid" )
             << CustomStyle( p.className()+"/Grid", new CustomPenColor( Color::Red ) )
             << p 
             << CustomStyle( p.className()+"/Grid", new CustomPenColor( Color::Black ) ); 
       
      Point prev = p; 
      for (++it; it != ite; ++it, prev = p)
        {//for all other points
          //conversion
          p = *it; 
          //display
          aBoard << p; 
          if (prev != p)
            aBoard.drawArrow(prev[0], prev[1], p[0], p[1]); 
        }
 
      //display the last edge too
      if (isClosed)
        {
          if (prev != p1)
            aBoard.drawArrow(prev[0], prev[1], p1[0], p1[1]); 
        }
    }
}

References DGtal::Color::Black, and DGtal::Color::Red.

Referenced by alphaShape().

main()

int main	(	int	argc,
		char **	argv
	)

Main procedure. Draw the convex hull and alpha-shape (for several values of alpha) of a point set coming from the digitization of a disk.

Parameters

argc	number of arguments
argv	array of arguments

Definition at line 339 of file exampleAlphaShape.cpp.

{
  trace.beginBlock ( "Example exampleAlphaShape" );
  trace.info() << "Args:";
  for ( int i = 0; i < argc; ++i )
    trace.info() << " " << argv[ i ];
  trace.info() << endl;
 
  alphaShape(); 
 
  trace.endBlock(); 
 
  return 0;
}

References alphaShape(), DGtal::Trace::beginBlock(), DGtal::Trace::endBlock(), DGtal::Trace::info(), and DGtal::trace.