DGtal  1.2.beta
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
grid-curve-dig-convexity.png
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( int argc, char** argv )
{
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 ( unsigned int i = 0; i < T.size(); ++i )
for ( unsigned int j = i+2; j < T.size(); ++j )
{
aBoard.setPenColorRGBi( rand() % 255, rand() % 255, rand() % 255 );
unsigned int 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();
}
aBoard.setPenColor( Color::Black );
aBoard << c;
aBoard.saveEPS( "myGridCurve.eps", Board2D::BoundingBox );//, 5000 );
return 0;
}
// //