ENH: make ApplyToImageMetadata available in Python wrapping

Modules/Core/Transform/include/itkTransform.h

@@ -27,6 +27,7 @@
 #include "vnl/vnl_vector_fixed.h"
 #include "vnl/vnl_matrix_fixed.h"
 #include "itkMatrix.h"
+#include "itkImageBase.h"
 
 namespace itk
 {
@@ -542,22 +543,43 @@ class ITK_TEMPLATE_EXPORT Transform : public TransformBaseTemplate<TParametersVa
    *
    * Updates image metadata (origin, spacing, direction cosines matrix) in place.
    *
-   * Only available when input and output space are of the same dimension.
+   * In C++, only available when input and output space are of the same dimension.
    * Only works properly for linear transforms.
    *
    * The image parameter may be either a SmartPointer or a raw pointer.
    * */
   /** @ITKStartGrouping */
+#if defined(ITK_WRAPPING_PARSER) || defined(SWIG_VERSION)
+  // This variant is only available in the wrapped languages.
+  // Make it unavailable in C++ to avoid being called when the versions above do not match.
+  void
+  ApplyToImageMetadata(ImageBase<VInputDimension> * image) const
+  {
+    if (VInputDimension != VOutputDimension)
+    {
+      itkExceptionMacro("ApplyToImageMetadata is only usable with transforms with equal input and output dimensions."
+                        " This class is: "
+                        << this->GetNameOfClass());
+    }
+    this->ApplyToImageMetadataInternal(image);
+  }
+#else
+  // These two variants are only available in C++ (assuming same in/out dimensions).
   template <typename TImage>
   std::enable_if_t<TImage::ImageDimension == VInputDimension && TImage::ImageDimension == VOutputDimension, void>
-  ApplyToImageMetadata(TImage * image) const;
+  ApplyToImageMetadata(TImage * image) const
+  {
+    this->ApplyToImageMetadataInternal(image);
+  }
   template <typename TImage>
   std::enable_if_t<TImage::ImageDimension == VInputDimension && TImage::ImageDimension == VOutputDimension, void>
   ApplyToImageMetadata(SmartPointer<TImage> image) const
   {
-    this->ApplyToImageMetadata(image.GetPointer()); // Delegate to the raw pointer signature
+    this->ApplyToImageMetadataInternal(image.GetPointer());
   }
+#endif
   /** @ITKEndGrouping */
+
 protected:
   /**
    * Clone the current transform.
@@ -591,6 +613,10 @@ class ITK_TEMPLATE_EXPORT Transform : public TransformBaseTemplate<TParametersVa
   }
 
 private:
+  /** Implementation of ApplyToImageMetadata. */
+  void
+  ApplyToImageMetadataInternal(ImageBase<VInputDimension> * image) const;
+
   template <typename TType>
   static std::string
   GetTransformTypeAsString(TType *)

Modules/Core/Transform/include/itkTransform.hxx

@@ -456,52 +456,60 @@ Transform<TParametersValueType, VInputDimension, VOutputDimension>::TransformSym
 }
 
 template <typename TParametersValueType, unsigned int VInputDimension, unsigned int VOutputDimension>
-template <typename TImage>
-std::enable_if_t<TImage::ImageDimension == VInputDimension && TImage::ImageDimension == VOutputDimension, void>
-Transform<TParametersValueType, VInputDimension, VOutputDimension>::ApplyToImageMetadata(TImage * image) const
+void
+Transform<TParametersValueType, VInputDimension, VOutputDimension>::ApplyToImageMetadataInternal(
+  ImageBase<VInputDimension> * image) const
 {
-  using ImageType = TImage;
-
-  if (!this->IsLinear())
+  if constexpr (VInputDimension == VOutputDimension)
   {
-    itkWarningMacro("ApplyToImageMetadata was invoked with non-linear transform of type: "
-                    << this->GetNameOfClass() << ". This might produce unexpected results.");
-  }
+    using ImageType = ImageBase<VInputDimension>;
 
-  const typename Self::Pointer inverse = this->GetInverseTransform();
-  if (inverse.IsNull())
-  {
-    itkExceptionMacro(
-      "ApplyToImageMetadata was invoked with non-invertible transform of type: " << this->GetNameOfClass());
-  }
-
-  // transform origin
-  typename ImageType::PointType origin = image->GetOrigin();
-  origin = inverse->TransformPoint(origin);
-  image->SetOrigin(origin);
+    if (!this->IsLinear())
+    {
+      itkWarningMacro("ApplyToImageMetadata was invoked with non-linear transform of type: "
+                      << this->GetNameOfClass() << ". This might produce unexpected results.");
+    }
 
-  typename ImageType::SpacingType   spacing = image->GetSpacing();
-  typename ImageType::DirectionType direction = image->GetDirection();
-  // transform direction cosines and compute new spacing
-  for (unsigned int i = 0; i < ImageType::ImageDimension; ++i)
-  {
-    Vector<typename Self::ParametersValueType, ImageType::ImageDimension> dirVector;
-    for (unsigned int k = 0; k < ImageType::ImageDimension; ++k)
+    const typename Self::Pointer inverse = this->GetInverseTransform();
+    if (inverse.IsNull())
     {
-      dirVector[k] = direction[k][i];
+      itkExceptionMacro(
+        "ApplyToImageMetadata was invoked with non-invertible transform of type: " << this->GetNameOfClass());
     }
 
-    dirVector *= spacing[i];
-    dirVector = inverse->TransformVector(dirVector);
-    spacing[i] = dirVector.Normalize();
+    // transform origin
+    typename ImageType::PointType origin = image->GetOrigin();
+    origin = inverse->TransformPoint(origin);
+    image->SetOrigin(origin);
 
-    for (unsigned int k = 0; k < ImageType::ImageDimension; ++k)
+    typename ImageType::SpacingType   spacing = image->GetSpacing();
+    typename ImageType::DirectionType direction = image->GetDirection();
+    // transform direction cosines and compute new spacing
+    for (unsigned int i = 0; i < ImageType::ImageDimension; ++i)
     {
-      direction[k][i] = dirVector[k];
+      Vector<typename Self::ParametersValueType, ImageType::ImageDimension> dirVector;
+      for (unsigned int k = 0; k < ImageType::ImageDimension; ++k)
+      {
+        dirVector[k] = direction[k][i];
+      }
+
+      dirVector *= spacing[i];
+      dirVector = inverse->TransformVector(dirVector);
+      spacing[i] = dirVector.Normalize();
+
+      for (unsigned int k = 0; k < ImageType::ImageDimension; ++k)
+      {
+        direction[k][i] = dirVector[k];
+      }
     }
+    image->SetDirection(direction);
+    image->SetSpacing(spacing);
+  }
+  else
+  {
+    itkExceptionMacro("ApplyToImageMetadata was invoked with transform of type: "
+                      << this->GetNameOfClass() << " that has different input and output dimensions.");
   }
-  image->SetDirection(direction);
-  image->SetSpacing(spacing);
 }
 
 

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

@@ -7,6 +7,15 @@ if(ITK_WRAP_PYTHON)
       ${ITK_EXAMPLE_DATA_ROOT}/DiagonalLines.png
   )
 
+  list(FIND ITK_WRAP_IMAGE_DIMS 3 wrap_3_index)
+  if(wrap_3_index GREATER -1)
+    itk_python_add_test(
+      NAME itkApplyToImageMetadataTest
+      COMMAND
+        ${CMAKE_CURRENT_SOURCE_DIR}/itkApplyToImageMetadataTest.py
+    )
+  endif()
+
   itk_python_expression_add_test(
     NAME PythonInstantiateBSplineTransform2D2D
     EXPRESSION "t = itk.BSplineTransform[itk.D, 2, 2].New()"

Modules/Core/Transform/wrapping/test/itkApplyToImageMetadataTest.py

@@ -0,0 +1,55 @@
+# ==========================================================================
+#
+#   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
+#
+#          https://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.F
+
+# Create a simple image with known origin, spacing and direction.
+ImageType = itk.Image[PixelType, Dimension]
+image = ImageType.New()
+size = itk.Size[Dimension]()
+size.Fill(4)
+region = itk.ImageRegion[Dimension]()
+region.SetSize(size)
+image.SetRegions(region)
+image.SetOrigin([1.0, 2.0, 3.0])
+image.SetSpacing([1.0, 1.0, 1.0])
+image.Allocate()
+
+# Build a translation transform, which is linear and invertible.
+TransformType = itk.TranslationTransform[itk.D, Dimension]
+transform = TransformType.New()
+translation = itk.Vector[itk.D, Dimension]()
+translation[0] = 10.0
+translation[1] = 20.0
+translation[2] = 30.0
+transform.Translate(translation)
+
+# Apply the transform to the image metadata, updating origin/spacing/direction
+# in place, without resampling the pixel data.
+transform.ApplyToImageMetadata(image)
+
+expected_origin = transform.GetInverseTransform().TransformPoint([1.0, 2.0, 3.0])
+
+for i in range(Dimension):
+    assert np.isclose(image.GetOrigin()[i], expected_origin[i])
+
+print("ApplyToImageMetadata Test Done")