WIP: Prototype of wrapping NRRD parsers in C++ locale

Used Claude to implement a prototype/test of using a string stream
with a set locale instead of sscanf.

Author: blowekamp

Modules/IO/NRRD/test/CMakeLists.txt

@@ -356,3 +356,8 @@ itk_add_test(
     itkNrrdMetaDataTest
     ${ITK_TEST_OUTPUT_DIR}
 )
+
+# GTest tests
+set(ITKIONRRDGTests itkNrrdLocaleGTest.cxx)
+
+creategoogletestdriver(ITKIONRRD "${ITKIONRRD-Test_LIBRARIES}" "${ITKIONRRDGTests}")

Modules/IO/NRRD/test/itkNrrdLocaleGTest.cxx

@@ -0,0 +1,176 @@
+/*=========================================================================
+ *
+ *  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.
+ *
+ *=========================================================================*/
+
+#include <locale.h>
+#include "itkImage.h"
+#include "itkImageFileReader.h"
+#include "itkImageFileWriter.h"
+#include "itkNrrdImageIO.h"
+#include "itksys/SystemTools.hxx"
+
+#include "itkGTest.h"
+
+#define _STRING(s) #s
+#define TOSTRING(s) std::string(_STRING(s))
+
+namespace
+{
+
+constexpr unsigned int Dimension = 3;
+using PixelType = float;
+using ImageType = itk::Image<PixelType, Dimension>;
+
+class NrrdLocaleTest : public ::testing::Test
+{
+public:
+  void
+  SetUp() override
+  {
+    itksys::SystemTools::ChangeDirectory(TOSTRING(ITK_TEST_OUTPUT_DIR));
+  }
+
+  ImageType::Pointer
+  CreateTestImage()
+  {
+    auto image = ImageType::New();
+
+    ImageType::SizeType size;
+    size.Fill(16);
+
+    ImageType::IndexType start;
+    start.Fill(0);
+
+    ImageType::RegionType region(start, size);
+    image->SetRegions(region);
+    image->Allocate();
+    image->FillBuffer(42.0f);
+
+    // Set spacing with fractional values that would be misparsed
+    // in locales using comma as decimal separator
+    ImageType::SpacingType spacing;
+    spacing[0] = 3.5;      // Would be parsed correctly even with truncation
+    spacing[1] = 0.878906; // Would become 0.0 in de_DE locale, causing error
+    spacing[2] = 2.2;      // Would be parsed incorrectly
+
+    image->SetSpacing(spacing);
+
+    // Set origin with fractional values
+    ImageType::PointType origin;
+    origin[0] = 1.5;
+    origin[1] = 2.75;
+    origin[2] = 0.5;
+    image->SetOrigin(origin);
+
+    return image;
+  }
+};
+
+TEST_F(NrrdLocaleTest, ReadWriteWithCLocale)
+{
+  auto       image = CreateTestImage();
+  const auto expectedSpacing = image->GetSpacing();
+  const auto expectedOrigin = image->GetOrigin();
+
+  const std::string filename = "locale_test.nrrd";
+
+  // Write the image with C locale
+  setlocale(LC_NUMERIC, "C");
+
+  auto writer = itk::ImageFileWriter<ImageType>::New();
+  writer->SetFileName(filename);
+  writer->SetInput(image);
+  writer->SetImageIO(itk::NrrdImageIO::New());
+  EXPECT_NO_THROW(writer->Update());
+
+  // Read with C locale
+  auto reader = itk::ImageFileReader<ImageType>::New();
+  reader->SetFileName(filename);
+  reader->SetImageIO(itk::NrrdImageIO::New());
+  EXPECT_NO_THROW(reader->Update());
+
+  const auto readImage = reader->GetOutput();
+  const auto readSpacing = readImage->GetSpacing();
+  const auto readOrigin = readImage->GetOrigin();
+
+  // Verify spacing
+  for (unsigned int i = 0; i < Dimension; ++i)
+  {
+    EXPECT_NEAR(readSpacing[i], expectedSpacing[i], 1e-6) << "Spacing mismatch in C locale at index " << i;
+  }
+
+  // Verify origin
+  for (unsigned int i = 0; i < Dimension; ++i)
+  {
+    EXPECT_NEAR(readOrigin[i], expectedOrigin[i], 1e-6) << "Origin mismatch in C locale at index " << i;
+  }
+}
+
+TEST_F(NrrdLocaleTest, ReadWithGermanLocale)
+{
+  auto       image = CreateTestImage();
+  const auto expectedSpacing = image->GetSpacing();
+  const auto expectedOrigin = image->GetOrigin();
+
+  const std::string filename = "locale_test_de.nrrd";
+
+  // Write the image with C locale
+  setlocale(LC_NUMERIC, "C");
+
+  auto writer = itk::ImageFileWriter<ImageType>::New();
+  writer->SetFileName(filename);
+  writer->SetInput(image);
+  writer->SetImageIO(itk::NrrdImageIO::New());
+  EXPECT_NO_THROW(writer->Update());
+
+  // Try to set German locale; skip test if not available
+  if (setlocale(LC_NUMERIC, "de_DE.UTF-8") == nullptr)
+  {
+    GTEST_SKIP() << "de_DE.UTF-8 locale not available, skipping locale-specific test";
+  }
+
+  // Read with de_DE locale - this is the critical test
+  auto reader = itk::ImageFileReader<ImageType>::New();
+  reader->SetFileName(filename);
+  reader->SetImageIO(itk::NrrdImageIO::New());
+  EXPECT_NO_THROW(reader->Update());
+
+  const auto readImage = reader->GetOutput();
+  const auto readSpacing = readImage->GetSpacing();
+  const auto readOrigin = readImage->GetOrigin();
+
+  // Verify spacing - this would fail without locale-independent parsing
+  for (unsigned int i = 0; i < Dimension; ++i)
+  {
+    EXPECT_NEAR(readSpacing[i], expectedSpacing[i], 1e-6)
+      << "Spacing mismatch in de_DE locale at index " << i
+      << ". This indicates locale-dependent parsing is still occurring!";
+  }
+
+  // Verify origin
+  for (unsigned int i = 0; i < Dimension; ++i)
+  {
+    EXPECT_NEAR(readOrigin[i], expectedOrigin[i], 1e-6)
+      << "Origin mismatch in de_DE locale at index " << i
+      << ". This indicates locale-dependent parsing is still occurring!";
+  }
+
+  // Restore C locale
+  setlocale(LC_NUMERIC, "C");
+}
+
+} // namespace

Modules/ThirdParty/NrrdIO/src/NrrdIO/CMakeLists.txt

@@ -8,7 +8,7 @@ INCLUDE_REGULAR_EXPRESSION("^.*.h$")
 # package. See http://teem.sourceforge.net for more information.
 #
 
-SET(nrrdio_SRCS 754.c mop.c array.c parseAir.c dio.c sane.c endianAir.c
+SET(nrrdio_SRCS 754.c mop.c array.c parseAir.cxx dio.c sane.c endianAir.c
 string.c enum.c miscAir.c biffbiff.c biffmsg.c accessors.c defaultsNrrd.c
 enumsNrrd.c arraysNrrd.c methodsNrrd.c reorder.c axis.c simple.c comment.c
 keyvalue.c endianNrrd.c parseNrrd.c gzio.c read.c write.c format.c