geometry/curves/exampleDigitalConvexity.cpp

This snippet shows how to identify and display digital fully subconvex sets of a grid curve form its tangent bundle.

See also

Digital convexity, full convexity and P-convexity

Extraction of all subconvex triangles to the digital curve.

 

 

#include <iostream>
 
#include "DGtal/base/Common.h"
#include "DGtal/helpers/StdDefs.h"
#include "ConfigExamples.h"
 
#include "DGtal/geometry/curves/FreemanChain.h"
#include "DGtal/geometry/curves/GridCurve.h"
#include "DGtal/geometry/volumes/DigitalConvexity.h"
 
#include "DGtal/io/boards/Board2D.h"

 
using namespace std;
using namespace DGtal;
using namespace Z2i;
 

int main( )
{
  trace.beginBlock ( "Example for 2d gridcurves" );
  string S = examplesPath + "samples/contourS.fc";
 
  // domain
  const Point lowerBound( -200, -200 );
  const Point upperBound( 200, 200 );
 
  fstream inputStream( S.c_str(), ios::in );
  FreemanChain<int> fc(inputStream);
  inputStream.close();
  Curve c;
  c.initFromPointsRange( fc.begin(), fc.end() );
  auto points = c.getPointsRange();
  std::vector<Point> T( points.begin(), points.end() );
  Board2D aBoard;
  aBoard.setUnit(Board2D::UCentimeter);
  DigitalConvexity<KSpace> dconv( lowerBound, upperBound );
  auto c_cover = dconv.makeCellCover( T.begin(), T.end(), 1, 1 );
  const float sx = -0.5;
  const float sy = -0.5;
  trace.beginBlock( "Compute fully subconvex sets" );
  for ( size_t i = 0; i < T.size(); ++i )
    for ( size_t j = i+2; j < T.size(); ++j )
      {
        aBoard.setPenColorRGBi( rand() % 255, rand() % 255, rand() % 255 );
        size_t k = (i+j)/2;
        if ( ! dconv.isSimplexFullDimensional( { T[i], T[j], T[k] } ) ) continue;
        auto triangle = dconv.makeSimplex( { T[i], T[j], T[k] } );
        if ( dconv.isFullySubconvex( triangle, c_cover ) )
          {
            aBoard.drawLine( sx+(float)T[i][0], sy+(float)T[i][1],
                             sx+(float)T[j][0], sy+(float)T[j][1] );
            aBoard.drawLine( sx+(float)T[i][0], sy+(float)T[i][1],
                             sx+(float)T[k][0], sy+(float)T[k][1] );
            aBoard.drawLine( sx+(float)T[k][0], sy+(float)T[k][1],
                             sx+(float)T[j][0], sy+(float)T[j][1] );
          }
        else
          j = T.size();
      }
  trace.endBlock();
  aBoard.setPenColor( Color::Black );
  aBoard << c;
  aBoard.saveEPS( "myGridCurve.eps", Board2D::BoundingBox );//, 5000 );
  trace.endBlock();
  return 0;
}
//                                                                           //