geometry/curves/exampleFrechetShortcut.cpp

This snippet segments a digital curve into Frechet shortcuts.

See also

Fréchet Shortcuts and Analysis of one-dimensional discrete structures

 
#include <iostream>
#include "DGtal/base/Common.h"
#include "DGtal/helpers/StdDefs.h"
 
#include "ConfigExamples.h"
#include "DGtal/io/boards/Board2D.h"
#include "DGtal/geometry/curves/FrechetShortcut.h"
#include "DGtal/geometry/curves/GreedySegmentation.h"
 
using namespace std;
using namespace DGtal;
using namespace Z2i;
 
 
 
 
 
int main( int argc, char** argv )
{
  trace.beginBlock ( "Example FrechetShortcut" );
  trace.info() << "Args:";
  for ( int i = 0; i < argc; ++i )
    trace.info() << " " << argv[ i ];
  trace.info() << endl;
 
  std::string filename;
  double error;
  
  if(argc == 1)
    {
      trace.info() << "Use default file and error value\n";
      filename = examplesPath + "samples/plant-frechet.dat";
      error = 3;
    }
  else
    if(argc != 3)
      {
        trace.info() << "Please enter a filename and error value.\n";
        return 0;
      }
    else
      {
        filename = argv[1];
        error = atof(argv[2]);
      }
  ifstream instream; // input stream
  instream.open (filename.c_str(), ifstream::in);
  
 
  
  Curve c; //grid curve
  c.initFromVectorStream(instream);
  
  Board2D board;
  
  // Display the pixels as arrows range to show the way the curve is scanned
  board << c.getArrowsRange();
  
  trace.beginBlock("Simple example");
 
  Curve::PointsRange r = c.getPointsRange(); 
  
  typedef FrechetShortcut<Curve::PointsRange::ConstIterator,int> Shortcut;
  
  // Computation of one shortcut
  Shortcut s(error);
  
  s.init( r.begin() );
  while ( ( s.end() != r.end() )
          &&( s.extendFront() ) ) {}
  
 
 
  // Computation of a greedy segmentation
  
  typedef GreedySegmentation<Shortcut> Segmentation;
  
  Segmentation theSegmentation( r.begin(), r.end(), Shortcut(error) );
  
  // the segmentation is computed here
  Segmentation::SegmentComputerIterator it = theSegmentation.begin();
  Segmentation::SegmentComputerIterator itEnd = theSegmentation.end();
 
  for ( ; it != itEnd; ++it) {
    s=Shortcut(*it);
    trace.info() << s << std::endl;
    board << s; 
  }
  
  board.saveEPS("FrechetShortcutExample.eps", Board2D::BoundingBox, 5000 ); 
 
  #ifdef WITH_CAIRO
    board.saveCairo("FrechetShortcutExample.png"); 
  #endif
 
 
  trace.endBlock();
  return 0;
}
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