ENH: Add GetPreviousTransformConfiguration to ElastixBase

Used to slightly simplify `TransformBase<TElastix>::ReadFromFile()`.
SuperElastix · Mar 23, 2023 · b261946 · b261946
1 parent 38b6152
commit b261946
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Showing 3 changed files with 26 additions and 10 deletions.
diff --git a/Core/ComponentBaseClasses/elxTransformBase.hxx b/Core/ComponentBaseClasses/elxTransformBase.hxx
@@ -341,18 +341,14 @@ TransformBase<TElastix>::ReadFromFile()
   /** Call the function ReadInitialTransformFromFile. */
   if (fileName == "NoInitialTransform")
   {
-    const auto numberOfConfigurations = elastixBase.GetNumberOfTransformConfigurations();
-
-    if ((numberOfConfigurations > 1) && (&configuration != elastixBase.GetTransformConfiguration(0)))
+    if (elastixBase.GetNumberOfTransformConfigurations() > 1)
     {
-      for (size_t index{ 1 }; index < numberOfConfigurations; ++index)
+      const Configuration::ConstPointer previousTransformConfiguration =
+        elastixBase.GetPreviousTransformConfiguration(configuration);
+
+      if (previousTransformConfiguration)
       {
-        if (elastixBase.GetTransformConfiguration(index) == &configuration)
-        {
-          // Use the previous configuration (at position index - 1) for the initial transform.
-          this->ReadInitialTransformFromConfiguration(elastixBase.GetTransformConfiguration(index - 1));
-          break;
-        }
+        this->ReadInitialTransformFromConfiguration(previousTransformConfiguration);
       }
     }
   }

diff --git a/Core/Kernel/elxElastixBase.cxx b/Core/Kernel/elxElastixBase.cxx
@@ -497,6 +497,21 @@ ElastixBase::GetTransformConfiguration(const size_t index) const
 }
 
 
+/**
+ * ************** GetPreviousTransformConfiguration *********************
+ */
+
+Configuration::ConstPointer
+ElastixBase::GetPreviousTransformConfiguration(const Configuration & configuration) const
+{
+  const auto begin = m_TransformConfigurations.cbegin();
+  const auto end = m_TransformConfigurations.cend();
+  const auto found = std::find(begin, end, &configuration);
+
+  return (found == begin || found == end) ? nullptr : *(found - 1);
+}
+
+
 /**
  * ************** GetNumberOfTransformConfigurations *********************
  */

diff --git a/Core/Kernel/elxElastixBase.h b/Core/Kernel/elxElastixBase.h
@@ -356,6 +356,11 @@ class ElastixBase
   Configuration::ConstPointer
   GetTransformConfiguration(const size_t index) const;
 
+  /** Returns the transformation configuration just before the specified one, or null. Returns null if the specified
+   * configuration does not have a previous one in the vector of transformation configurations. */
+  Configuration::ConstPointer
+  GetPreviousTransformConfiguration(const Configuration & configuration) const;
+
   /** Returns the number of configurations in the vector of transformation configurations. */
   size_t
   GetNumberOfTransformConfigurations() const;