ENH: output label starts from 1

include/lsgrmGraphOperations.txx

@@ -101,7 +101,7 @@ MergeAllGraphsAndAchieveSegmentation(
   using LabelImageIterator = itk::ImageRegionIterator<typename TSegmenter::LabelImageType>;
   LabelImageIterator it(labelImage, labelImage->GetLargestPossibleRegion());
   const typename TSegmenter::LabelImageType::InternalPixelType noDataLabel = 0;
-  typename TSegmenter::LabelImageType::InternalPixelType label = 1;
+  typename TSegmenter::LabelImageType::InternalPixelType label;
 
   // Get the maximum label value
   for(it.GoToBegin();!it.IsAtEnd(); ++it)
@@ -109,6 +109,7 @@ MergeAllGraphsAndAchieveSegmentation(
       label = it.Get();
 
   // Compute LUT
+  label = 1;
   vnl_vector<typename TSegmenter::LabelImageType::InternalPixelType> lut(label,noDataLabel);
   for(it.GoToBegin();!it.IsAtEnd(); ++it)
     {