ITK  5.0.0
Insight Segmentation and Registration Toolkit
WikiExamples/SimpleOperations/DistanceBetweenIndices.cxx
#include "itkPoint.h"
#include "itkIndex.h"
#include <iostream>
#include <string>
int main(int, char *[])
{
itk::Index<2> pixel1;
pixel1.Fill(2);
itk::Index<2> pixel2;
pixel2.Fill(4);
p1[0] = pixel1[0];
p1[1] = pixel1[1];
p2[0] = pixel2[0];
p2[1] = pixel2[1];
double distance = p2.EuclideanDistanceTo(p1);
std::cout << "Distance: " << distance << std::endl;
return EXIT_SUCCESS;
}