geometry/volumes/distance/distancetransform2D.cpp

Example of distance transformation in dimension 2.

See also

nD Volumetric Analysis using Separable Processes

Distance transform with L2 norm.

#include <iostream>
#include <iomanip>
#include "DGtal/base/Common.h"
#include "DGtal/helpers/StdDefs.h"
#include "DGtal/io/colormaps/GrayscaleColorMap.h"
#include "DGtal/io/colormaps/HueShadeColorMap.h"
#include "DGtal/io/colormaps/TickedColorMap.h"
#include "DGtal/io/colormaps/GradientColorMap.h"
#include "DGtal/io/boards/Board2D.h"
#include "DGtal/images/ImageSelector.h"
#include "DGtal/images/SimpleThresholdForegroundPredicate.h"
#include "DGtal/geometry/volumes/distance/DistanceTransformation.h"

using namespace std;
using namespace DGtal;


template<typename Image>
void randomSeeds(Image &image, const unsigned int nb, const int value)
{
  typename Image::Point p, low = image.domain().lowerBound();
  typename Image::Vector ext;

  ext = image.extent();

  for (unsigned int k = 0 ; k < nb; k++)
  {
    for (unsigned int dim = 0; dim < Image::dimension; dim++)
      p[dim] = rand() % (ext[dim]) +  low[dim];
    
    image.setValue(p, value);
  }
}

int main()
{
  trace.beginBlock ( "Example distancetransform2D" );

  Z2i::Point a ( 0, 0 );
  Z2i::Point b ( 127, 127);
  
  //Input image with unsigned char values
  typedef ImageSelector<Z2i::Domain, unsigned int>::Type Image;
  Image image ( Z2i::Domain(a, b ));

  //We fill the image with the 128 value
  for ( Image::Iterator it = image.begin(), itend = image.end();it != itend; ++it)
    (*it)=128;
  //We generate 16 seeds with 0 values.
  randomSeeds(image,16,0);

  //Input shape output
  typedef GrayscaleColorMap<Image::Value> Gray;
  Board2D board;
  board.setUnit ( LibBoard::Board::UCentimeter );
  Display2DFactory::drawImage<Gray>(board, image, (unsigned int)0, (unsigned int)129);
  board.saveSVG("inputShape.svg");

  //Point Predicate from random seed image
  typedef functors::SimpleThresholdForegroundPredicate<Image> PointPredicate;
  PointPredicate predicate(image,0);

  typedef  DistanceTransformation<Z2i::Space, PointPredicate, Z2i::L2Metric> DTL2;
  typedef  DistanceTransformation<Z2i::Space, PointPredicate, Z2i::L1Metric> DTL1;
 
 
  DTL2 dtL2(image.domain(), predicate, Z2i::l2Metric);
  DTL1 dtL1(image.domain(), predicate, Z2i::l1Metric);


  DTL2::Value maxv2=0;
  //We compute the maximum DT value on the L2 map
  for ( DTL2::ConstRange::ConstIterator it = dtL2.constRange().begin(), itend = dtL2.constRange().end();it != itend; ++it)
    if ( (*it) > maxv2)  maxv2 = (*it);
 
  DTL1::Value maxv1=0;
  //We compute the maximum DT value on the L1 map
  for ( DTL1::ConstRange::ConstIterator it = dtL1.constRange().begin(), itend = dtL1.constRange().end();it != itend; ++it)
    if ( (*it) > maxv1)  maxv1 = (*it);
  
  //Colormap used for the SVG output
  typedef HueShadeColorMap<DTL2::Value, 2> HueTwice;


  
  
  trace.warning() << dtL2 << " maxValue= "<<maxv2<< endl;
  board.clear();
  Display2DFactory::drawImage<HueTwice>(board, dtL2, 0.0, maxv2 + 1);
  board.saveSVG ( "example-DT-L2.svg" );

  trace.warning() << dtL1 << " maxValue= "<<maxv1<< endl;
  board.clear();
  Display2DFactory::drawImage<HueTwice>(board, dtL1, 0.0, maxv1 + 1);
  board.saveSVG ( "example-DT-L1.svg" );

  //Explicit export with ticked colormap
  //We compute the maximum DT value on the L2 map
  board.clear();
  TickedColorMap<double, GradientColorMap<double> > ticked(0.0,maxv2, Color::White);
  ticked.addRegularTicks(5, 0.5);
  ticked.finalize();
  ticked.colormap()->addColor( Color::Red );
  ticked.colormap()->addColor( Color::Black );
  for ( DTL2::Domain::ConstIterator it = dtL2.domain().begin(), itend = dtL2.domain().end();it != itend; ++it)
  {
    board<< CustomStyle((*it).className(),new CustomColors(ticked(dtL2(*it)),ticked(dtL2(*it))));
    board << *it;
  }
  board.saveSVG("example-DT-L2-ticked.svg");
  
  trace.endBlock();
  return 0;
}
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