--- a
+++ b/src/labelOverlapMeasures.cxx
@@ -0,0 +1,110 @@
+
+#include <nanobind/nanobind.h>
+#include <nanobind/stl/vector.h>
+#include <nanobind/stl/string.h>
+#include <nanobind/stl/tuple.h>
+#include <nanobind/stl/list.h>
+#include <nanobind/ndarray.h>
+#include <nanobind/stl/shared_ptr.h>
+
+#include <exception>
+#include <vector>
+#include <string>
+
+#include "itkImage.h"
+#include "itkLabelOverlapMeasuresImageFilter.h"
+
+#include "antsImage.h"
+
+namespace nb = nanobind;
+using namespace nb::literals;
+
+template<class PrecisionType, unsigned int ImageDimension>
+nb::dict labelOverlapMeasures( AntsImage<itk::Image<PrecisionType, ImageDimension>> &  antsSourceImage,
+                                AntsImage<itk::Image<PrecisionType, ImageDimension>> &  antsTargetImage )
+{
+  using ImageType = itk::Image<PrecisionType, ImageDimension>;
+  using ImagePointerType = typename ImageType::Pointer;
+
+  typename ImageType::Pointer itkSourceImage = antsSourceImage.ptr;
+  typename ImageType::Pointer itkTargetImage = antsTargetImage.ptr;
+
+  using FilterType = itk::LabelOverlapMeasuresImageFilter<ImageType>;
+  typename FilterType::Pointer filter = FilterType::New();
+  filter->SetSourceImage( itkSourceImage );
+  filter->SetTargetImage( itkTargetImage );
+  filter->Update();
+
+  typename FilterType::MapType labelMap = filter->GetLabelSetMeasures();
+
+  // Sort the labels
+
+  std::vector<PrecisionType> allLabels;
+  allLabels.clear();
+  for( typename FilterType::MapType::const_iterator it = labelMap.begin();
+       it != labelMap.end(); ++it )
+    {
+    if( (*it).first == 0 )
+      {
+      continue;
+      }
+
+    const int label = (*it).first;
+    allLabels.push_back( label );
+    }
+  std::sort( allLabels.begin(), allLabels.end() );
+
+
+  // Now put the results in an Rcpp data frame
+
+  unsigned int vectorLength = 1 + allLabels.size();
+
+  std::vector<PrecisionType> labels( vectorLength );
+  std::vector<double> totalOrTargetOverlap( vectorLength );
+  std::vector<double> unionOverlap( vectorLength );
+  std::vector<double> meanOverlap( vectorLength );
+  std::vector<double> volumeSimilarity( vectorLength );
+  std::vector<double> falseNegativeError( vectorLength );
+  std::vector<double> falsePositiveError( vectorLength );
+
+  // We'll replace label '0' with "All" in the R wrapper.
+  labels[0] = itk::NumericTraits<PrecisionType>::Zero;
+  totalOrTargetOverlap[0] = filter->GetTotalOverlap();
+  unionOverlap[0] = filter->GetUnionOverlap();
+  meanOverlap[0] = filter->GetMeanOverlap();
+  volumeSimilarity[0] = filter->GetVolumeSimilarity();
+  falseNegativeError[0] = filter->GetFalseNegativeError();
+  falsePositiveError[0] = filter->GetFalsePositiveError();
+
+  unsigned int i = 1;
+  typename std::vector<PrecisionType>::const_iterator itL = allLabels.begin();
+  for( itL = allLabels.begin(); itL != allLabels.end(); ++itL )
+    {
+    labels[i] = *itL;
+    totalOrTargetOverlap[i] = filter->GetTargetOverlap( *itL );
+    unionOverlap[i] = filter->GetUnionOverlap( *itL );
+    meanOverlap[i] = filter->GetMeanOverlap( *itL );
+    volumeSimilarity[i] = filter->GetVolumeSimilarity( *itL );
+    falseNegativeError[i] = filter->GetFalseNegativeError( *itL );
+    falsePositiveError[i] = filter->GetFalsePositiveError( *itL );
+    i++;
+    }
+
+  nb::dict labelOverlapMeasures;
+  labelOverlapMeasures["Label"] = labels;
+  labelOverlapMeasures["TotalOrTargetOverlap"] = totalOrTargetOverlap;
+  labelOverlapMeasures["UnionOverlap"] = unionOverlap;
+  labelOverlapMeasures["MeanOverlap"] = meanOverlap;
+  labelOverlapMeasures["VolumeSimilarity"] = volumeSimilarity;
+  labelOverlapMeasures["FalseNegativeError"] = falseNegativeError;
+  labelOverlapMeasures["FalsePositiveError"] = falsePositiveError;
+
+  return labelOverlapMeasures;
+}
+
+void local_labelOverlapMeasures(nb::module_ &m)
+{
+  m.def("labelOverlapMeasures2D", &labelOverlapMeasures<unsigned int, 2>);
+  m.def("labelOverlapMeasures3D", &labelOverlapMeasures<unsigned int, 3>);
+  m.def("labelOverlapMeasures4D", &labelOverlapMeasures<unsigned int, 4>);
+}