ENH: Declare MakeOutput member function of three filters public

Paved the way for those filters to use `ProcessObject::MakeRequiredOutputs`.

`MakeOutput` member functions are usually declared public, rather than protected.

Author: N-Dekker

Modules/Numerics/Statistics/include/itkCovarianceSampleFilter.h

@@ -121,12 +121,6 @@ class ITK_TEMPLATE_EXPORT CovarianceSampleFilter : public ProcessObject
   MeasurementVectorSizeType
   GetMeasurementVectorSize() const;
 
-protected:
-  CovarianceSampleFilter();
-  ~CovarianceSampleFilter() override = default;
-  void
-  PrintSelf(std::ostream & os, Indent indent) const override;
-
   /** DataObject pointer */
   using DataObjectPointer = DataObject::Pointer;
 
@@ -135,6 +129,12 @@ class ITK_TEMPLATE_EXPORT CovarianceSampleFilter : public ProcessObject
   DataObjectPointer
   MakeOutput(DataObjectPointerArraySizeType index) override;
 
+protected:
+  CovarianceSampleFilter();
+  ~CovarianceSampleFilter() override = default;
+  void
+  PrintSelf(std::ostream & os, Indent indent) const override;
+
   void
   GenerateData() override;
 }; // end of class

Modules/Numerics/Statistics/include/itkStandardDeviationPerComponentSampleFilter.h

@@ -98,12 +98,6 @@ class ITK_TEMPLATE_EXPORT StandardDeviationPerComponentSampleFilter : public Pro
   const MeasurementVectorRealDecoratedType *
   GetMeanPerComponentOutput() const;
 
-protected:
-  StandardDeviationPerComponentSampleFilter();
-  ~StandardDeviationPerComponentSampleFilter() override = default;
-  void
-  PrintSelf(std::ostream & os, Indent indent) const override;
-
   /** DataObject pointer */
   using DataObjectPointer = DataObject::Pointer;
 
@@ -112,6 +106,12 @@ class ITK_TEMPLATE_EXPORT StandardDeviationPerComponentSampleFilter : public Pro
   DataObjectPointer
   MakeOutput(DataObjectPointerArraySizeType index) override;
 
+protected:
+  StandardDeviationPerComponentSampleFilter();
+  ~StandardDeviationPerComponentSampleFilter() override = default;
+  void
+  PrintSelf(std::ostream & os, Indent indent) const override;
+
   void
   GenerateData() override;
 

Modules/Registration/Common/include/itkBlockMatchingImageFilter.h

@@ -160,12 +160,12 @@ class ITK_TEMPLATE_EXPORT BlockMatchingImageFilter : public MeshToMeshFilter<TFe
     return dynamic_cast<SimilaritiesType *>(this->ProcessObject::GetOutput(1));
   }
 
-protected:
   /** MakeOutput is provided for handling multiple outputs */
   using Superclass::MakeOutput;
   DataObject::Pointer
   MakeOutput(ProcessObject::DataObjectPointerArraySizeType idx) override;
 
+protected:
   /** We need to create our own GenerateOutputInformation because the
    * default version from ProcessObject result in a dynamic_cast of the input
    * pointer to the output pointer type in PointSet::CopyInformation.  This does