ENH: Adding Test for Array PixelType in Mesh Wrapping

Added test in Python to demonstrate the usage of Array PixelType in Mesh.
Usage of Array allows to change the size of pixeldata as per requirements later.
Using Array, however breaks the API support for SetElement and SetPointData in PointSet.
The only way to alter the data is through reference and for that CreateElementAt method is
used in the VectorContainer.

Author: PranjalSahu

Modules/Core/Mesh/wrapping/test/CMakeLists.txt

@@ -25,4 +25,6 @@ if(ITK_WRAP_PYTHON)
    EXPRESSION "instance = itk.RegularSphereMeshSource.New()")
   itk_python_expression_add_test(NAME itkSphereMeshSourcePythonTest
    EXPRESSION "instance = itk.SphereMeshSource.New()")
+
+  itk_python_add_test(NAME itkMeshArrayPixelTypePythonTest COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/itkMeshArrayPixelTypeTest.py)
 endif()

Modules/Core/Mesh/wrapping/test/itkMeshArrayPixelTypeTest.py

@@ -0,0 +1,62 @@
+# ==========================================================================
+#
+#   Copyright NumFOCUS
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#          http://www.apache.org/licenses/LICENSE-2.0.txt
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+# ==========================================================================*/
+import itk
+import numpy as np
+
+Dimension = 3
+PixelType = itk.Array.D
+NumberOfPoints = 10
+PixelDataSize = 5
+
+MeshType = itk.Mesh[PixelType, Dimension]
+mesh = MeshType.New()
+
+# Create Vector Container and Store values in it for each Point
+v = itk.VectorContainer[itk.UL, PixelType].New()
+v.Reserve(NumberOfPoints)
+
+for i in range(NumberOfPoints):
+    pixel_data_reference = v.CreateElementAt(i)
+    pixel_data_reference.SetSize(PixelDataSize)
+    pixel_data_reference.Fill(0)
+    pixel_data_reference[0] = i
+    pixel_data_reference[4] = i+4
+
+# Set the point data container
+mesh.SetPointData(v)
+
+assert mesh.GetPointData().Size() == NumberOfPoints
+assert mesh.GetPointData().ElementAt(0)[0] == 0
+assert mesh.GetPointData().ElementAt(0)[4] == 4
+assert mesh.GetPointData().ElementAt(2)[0] == 2+0
+assert mesh.GetPointData().ElementAt(2)[4] == 2+4
+
+# resize the PixelDataSize to see if it can be altered succesfully
+PixelDataSize = 10
+for i in range(NumberOfPoints):
+    pixel_data_reference = v.CreateElementAt(i)
+    pixel_data_reference.SetSize(PixelDataSize)
+    pixel_data_reference.Fill(0)
+    pixel_data_reference[0] = i
+    pixel_data_reference[9] = i+10
+
+assert mesh.GetPointData().Size() == NumberOfPoints
+assert mesh.GetPointData().ElementAt(0)[0] == 0
+assert mesh.GetPointData().ElementAt(0)[9] == 10
+assert mesh.GetPointData().ElementAt(2)[0] == 2+0
+assert mesh.GetPointData().ElementAt(2)[9] == 2+10