ENH: add missing metadata to DCMTKImageIO

Modules/IO/DCMTK/include/itkDCMTKFileReader.h

@@ -35,6 +35,7 @@
 #include "dcmtk/dcmdata/dcsequen.h"
 #include "itkMacro.h"
 #include "itkImageIOBase.h"
+#include "itkMetaDataDictionary.h"
 
 class DcmSequenceOfItems;
 class DcmFileFormat;
@@ -498,6 +499,9 @@ class ITKIODCMTK_EXPORT DCMTKFileReader
   static bool
   IsImageFile(const std::string & filename);
 
+  void
+  PopulateMetaDataDictionary(MetaDataDictionary & dict) const;
+
 private:
   std::string      m_FileName;
   DcmFileFormat *  m_DFile{ nullptr };

Modules/IO/DCMTK/src/itkDCMTKFileReader.cxx

@@ -33,6 +33,7 @@
 #include "dcmtk/dcmdata/dcvrus.h"    /* for DcmUnsignedShort */
 #include "dcmtk/dcmdata/dcvris.h"    /* for DcmIntegerString */
 #include "dcmtk/dcmdata/dcvrobow.h"  /* for DcmOtherByteOtherWord */
+#include "dcmtk/dcmdata/dcelem.h"    /* for DcmElement */
 #include "dcmtk/dcmdata/dcvrui.h"    /* for DcmUniqueIdentifier */
 #include "dcmtk/dcmdata/dcfilefo.h"  /* for DcmFileFormat */
 #include "dcmtk/dcmdata/dcmetinf.h"  /* for DcmMetaInfo */
@@ -47,7 +48,10 @@
 
 #include "vnl/vnl_cross.h"
 #include "itkIntTypes.h"
+#include "itkMetaDataObject.h"
+#include "itksys/Base64.h"
 #include <algorithm>
+#include <memory>
 
 namespace itk
 {
@@ -1369,6 +1373,72 @@ DCMTKFileReader::GetFileNumber() const
   return m_FileNumber;
 }
 
+void
+DCMTKFileReader::PopulateMetaDataDictionary(MetaDataDictionary & dict) const
+{
+  dict.Clear();
+  if (m_Dataset == nullptr)
+  {
+    return;
+  }
+  const unsigned long numElements = m_Dataset->card();
+  for (unsigned long i = 0; i < numElements; ++i)
+  {
+    DcmElement * element = m_Dataset->getElement(i);
+    if (element == nullptr)
+    {
+      continue;
+    }
+    const DcmTag & tag = element->getTag();
+    // Skip pixel data (7FE0,0010)
+    if (tag.getGroup() == 0x7fe0 && tag.getElement() == 0x0010)
+    {
+      continue;
+    }
+    // Format key as "GGGG|EEEE" (lowercase hex, matching GDCMImageIO)
+    char key[10];
+    std::snprintf(key, sizeof(key), "%04x|%04x", tag.getGroup(), tag.getElement());
+
+    const DcmEVR vr = element->getVR();
+    if (vr == EVR_SQ)
+    {
+      // Sequences are nested datasets, not byte arrays; getUint8Array() does
+      // not return their content.  Skip rather than emit an empty entry.
+      continue;
+    }
+    if (vr == EVR_OB || vr == EVR_OW || vr == EVR_OF || vr == EVR_OD || vr == EVR_OL || vr == EVR_OV || vr == EVR_UN ||
+        vr == EVR_ox || vr == EVR_px)
+    {
+      // Binary VR — base64-encode the raw bytes
+      Uint8 * byteValue = nullptr;
+      if (element->getUint8Array(byteValue) == EC_Normal && byteValue != nullptr)
+      {
+        const Uint32 length = element->getLength();
+        if (length > 0)
+        {
+          int encodedLengthEstimate = 2 * static_cast<int>(length);
+          encodedLengthEstimate = ((encodedLengthEstimate / 4) + 1) * 4;
+          const auto bin = std::make_unique<char[]>(encodedLengthEstimate);
+          const auto encodedLengthActual =
+            static_cast<unsigned int>(itksysBase64_Encode(reinterpret_cast<const unsigned char *>(byteValue),
+                                                          static_cast<SizeValueType>(length),
+                                                          reinterpret_cast<unsigned char *>(bin.get()),
+                                                          0));
+          EncapsulateMetaData<std::string>(dict, key, std::string(bin.get(), encodedLengthActual));
+        }
+      }
+    }
+    else
+    {
+      OFString value;
+      if (element->getOFStringArray(value) == EC_Normal)
+      {
+        EncapsulateMetaData<std::string>(dict, key, std::string(value.c_str()));
+      }
+    }
+  }
+}
+
 void
 DCMTKFileReader::AddDictEntry(DcmDictEntry * entry)
 {

Modules/IO/DCMTK/src/itkDCMTKImageIO.cxx

@@ -478,6 +478,7 @@ DCMTKImageIO::ReadImageInformation()
     this->m_Spacing.push_back(1.0);
   }
 
+  reader.PopulateMetaDataDictionary(this->GetMetaDataDictionary());
 
   this->OpenDicomImage();
   const DiPixel * interData = this->m_DImage->getInterData();

Modules/IO/DCMTK/test/CMakeLists.txt

@@ -2,6 +2,7 @@ itk_module_test()
 set(
   ITKIODCMTKTests
   itkDCMTKGetDicomTagsTest.cxx
+  itkDCMTKImageIOMetadataTest.cxx
   itkDCMTKImageIOMultiFrameImageTest.cxx
   itkDCMTKImageIONoPreambleTest.cxx
   itkDCMTKImageIOOrthoDirTest.cxx
@@ -82,6 +83,14 @@ itk_add_test(
     ${ITK_TEST_OUTPUT_DIR}/DICOMTags.txt
 )
 
+itk_add_test(
+  NAME itkDCMTKImageIOMetadataTest
+  COMMAND
+    ITKIODCMTKTestDriver
+    itkDCMTKImageIOMetadataTest
+    DATA{${ITK_DATA_ROOT}/Input/DicomSeries/Image0075.dcm}
+)
+
 itk_add_test(
   NAME itkDCMTKImageIOTest1
   COMMAND

Modules/IO/DCMTK/test/itkDCMTKImageIOMetadataTest.cxx

@@ -0,0 +1,76 @@
+/*=========================================================================
+ *
+ *  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 "itkDCMTKImageIO.h"
+#include "itkMetaDataObject.h"
+#include "itkTestingMacros.h"
+
+#include <iostream>
+
+// Tests that DCMTKImageIO::ReadImageInformation() populates the metadata
+// dictionary with DICOM tag values using "GGGG|EEEE" keys (lowercase
+// matching GDCMImageIO behavior). Expected values are verified against
+// Input/DicomSeries/Image0075.dcm using the same fixture as
+// itkDCMTKGetDicomTagsTest.
+int
+itkDCMTKImageIOMetadataTest(int argc, char * argv[])
+{
+  if (argc != 2)
+  {
+    std::cerr << "Missing parameters." << std::endl;
+    std::cerr << "Usage: " << itkNameOfTestExecutableMacro(argv) << " <DicomImage>" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  auto dcmtkIO = itk::DCMTKImageIO::New();
+
+  ITK_TEST_EXPECT_TRUE(dcmtkIO->CanReadFile(argv[1]));
+  dcmtkIO->SetFileName(argv[1]);
+  ITK_TRY_EXPECT_NO_EXCEPTION(dcmtkIO->ReadImageInformation());
+
+  const itk::MetaDataDictionary & dict = dcmtkIO->GetMetaDataDictionary();
+
+  // Dictionary must be populated
+  ITK_TEST_EXPECT_TRUE(!dict.GetKeys().empty());
+
+  // Pixel data (7FE0,0010) must NOT appear in the dictionary
+  ITK_TEST_EXPECT_TRUE(!dict.HasKey("7fe0|0010"));
+
+  // Verify string-valued DICOM tags using the "GGGG|EEEE" key format.
+  // Values are specific to the test file Input/DicomSeries/Image0075.dcm
+  std::string value;
+
+  // (0008,0021) DA  SeriesDate
+  ITK_TEST_EXPECT_TRUE(itk::ExposeMetaData<std::string>(dict, "0008|0021", value));
+  ITK_TEST_EXPECT_EQUAL(value, std::string("20030625"));
+
+  // (0010,0010) PN  PatientName
+  ITK_TEST_EXPECT_TRUE(itk::ExposeMetaData<std::string>(dict, "0010|0010", value));
+  ITK_TEST_EXPECT_EQUAL(value, std::string("Wes Turner"));
+
+  // (0010,0040) CS  PatientSex
+  ITK_TEST_EXPECT_TRUE(itk::ExposeMetaData<std::string>(dict, "0010|0040", value));
+  ITK_TEST_EXPECT_EQUAL(value, std::string("O"));
+
+  // (0028,0004) CS  PhotometricInterpretation
+  ITK_TEST_EXPECT_TRUE(itk::ExposeMetaData<std::string>(dict, "0028|0004", value));
+  ITK_TEST_EXPECT_EQUAL(value, std::string("MONOCHROME2"));
+
+  std::cout << "Test finished." << std::endl;
+  return EXIT_SUCCESS;
+}