ENH: Python dispatch on the first RequiredInputName

Dispatch Python filter types based on the type of the first
ProcessObject RequiredInputName, which is exposed in Python via
GetRequiredInputName and which can be the ProcessObject
PrimaryInputName.

This helps to address uses cases such as
`itk.elastix_registration_method`, where you still want to infer the
filter type based on the input fixed image type, but it may be passed in
as a keyword argument, such as
`itk.elastix_registration_method(moving_image=moving_image, fixed_image=fixed_image)`.

Re: InsightSoftwareConsortium#4858 InsightSoftwareConsortium/ITKElastix#212

Wrapping/Generators/Python/Tests/PythonTemplateTest.py

@@ -119,6 +119,17 @@
 median_kwarg = itk.MedianImageFilter.New(Input=reader.GetOutput())
 assert itk.class_(median) == itk.class_(median_kwarg)
 
+# filter type determined by the input passed as a primary input name input
+median_primary_kwarg = itk.MedianImageFilter.New(Primary=reader.GetOutput())
+assert itk.class_(median) == itk.class_(median_primary_kwarg)
+
+# First RequiredInputName: "FixedImage"
+fixed_image = reader.GetOutput()
+moving_image = fixed_image
+pde_registration = itk.PDEDeformableRegistrationFilter.New(
+    FixedImage=fixed_image, MovingImage=moving_image
+)
+
 # to a filter with a SetImage method
 calculator = itk.MinimumMaximumImageCalculator[ImageType].New(reader)
 # not GetImage() method here to verify it's the right image

Wrapping/Generators/Python/Tests/extras.py

@@ -163,6 +163,14 @@ def custom_callback(name, progress):
 image = itk.imread(filename, imageio=itk.PNGImageIO.New())
 assert type(image) == itk.Image[itk.RGBPixel[itk.UC], 2]
 
+# Python functional interface that determines the filter type
+# based on the primary input (dispatch)
+image = itk.imread(filename, itk.UC)
+# positional argument
+filtered = itk.median_image_filter(image)
+# required primary named input argument
+filtered = itk.median_image_filter(primary=image)
+
 # imread using a dicom series
 image = itk.imread(sys.argv[8])
 image0 = itk.imread(sys.argv[8], series_uid=0)

Wrapping/Generators/Python/itk/support/extras.py

@@ -39,6 +39,7 @@
 from .helpers import wasm_type_from_image_type, image_type_from_wasm_type
 from .helpers import wasm_type_from_mesh_type, mesh_type_from_wasm_type, python_to_js
 from .helpers import wasm_type_from_pointset_type, pointset_type_from_wasm_type
+from .helpers import snake_to_camel_case
 
 from .xarray import xarray_from_image, image_from_xarray
 
@@ -1552,17 +1553,6 @@ def search(s: str, case_sensitive: bool = False) -> List[str]:  # , fuzzy=True):
     return res
 
 
-def _snake_to_camel(keyword: str):
-    # Helpers for set_inputs snake case to CamelCase keyword argument conversion
-    _snake_underscore_re = re.compile("(_)([a-z0-9A-Z])")
-
-    def _underscore_upper(match_obj):
-        return match_obj.group(2).upper()
-
-    camel = keyword[0].upper()
-    if _snake_underscore_re.search(keyword[1:]):
-        return camel + _snake_underscore_re.sub(_underscore_upper, keyword[1:])
-    return camel + keyword[1:]
 
 
 def set_inputs(
@@ -1656,7 +1646,7 @@ def SetInputs(self, *args, **kargs):
         # (Ex: itk.ImageFileReader.UC2.New(SetFileName='image.png'))
         if attribName not in ["auto_progress", "template_parameters"]:
             if attribName.islower():
-                attribName = _snake_to_camel(attribName)
+                attribName = snake_to_camel_case(attribName)
             attrib = getattr(new_itk_object, "Set" + attribName)
 
             # Do not use try-except mechanism as this leads to
@@ -2162,7 +2152,7 @@ def ipython_kw_matches(text: str):
             namespace = split_name_parts[:-1]
             function_name = split_name_parts[-1]
             # Find corresponding object name
-            object_name = _snake_to_camel(function_name)
+            object_name = snake_to_camel_case(function_name)
             # Check that this object actually exists
             try:
                 object_callable_match = ".".join(namespace + [object_name])

Wrapping/Generators/Python/itk/support/helpers.py

@@ -40,6 +40,18 @@
     pass
 
 
+def snake_to_camel_case(keyword: str):
+    # Helpers for set_inputs snake case to CamelCase keyword argument conversion
+    _snake_underscore_re = re.compile("(_)([a-z0-9A-Z])")
+
+    def _underscore_upper(match_obj):
+        return match_obj.group(2).upper()
+
+    camel = keyword[0].upper()
+    if _snake_underscore_re.search(keyword[1:]):
+        return camel + _snake_underscore_re.sub(_underscore_upper, keyword[1:])
+    return camel + keyword[1:]
+
 def camel_to_snake_case(name):
     snake = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", name)
     snake = re.sub("([a-z0-9])([A-Z])", r"\1_\2", snake)

Wrapping/Generators/Python/itk/support/template_class.py

@@ -30,6 +30,7 @@
 from itk.support import base
 from itk.support.extras import output
 from itk.support.types import itkCType
+from itk.support.helpers import snake_to_camel_case
 import math
 from collections.abc import Mapping
 
@@ -718,6 +719,20 @@ def ttype_for_input_type(keys_l, input_type_l):
             # try to find a type suitable for the input provided
             input_type = output(cur).__class__
             keys = ttype_for_input_type(keys, input_type)
+        else:
+            inst = self.values()[0].New()
+            if hasattr(inst, "GetRequiredInputNames"):
+                required_input_names = inst.GetRequiredInputNames()
+                if len(required_input_names) > 0:
+                    primary_input_name = required_input_names[0]
+                    kwargs_camel = {snake_to_camel_case(k): v for k,v in kwargs.items()}
+                    if primary_input_name in kwargs_camel.keys():
+                        input_type = output(kwargs_camel[primary_input_name]).__class__
+                        keys = ttype_for_input_type(keys, input_type)
+                        if not hasattr(inst, f"Set{primary_input_name}"):
+                            arg_0 = kwargs_camel.pop(primary_input_name)
+                            kwargs = kwargs_camel
+                            args = (arg_0,) + args
 
         if len(keys) == 0:
             if not input_type: