STYLE: Remove == true from Boolean expressions

Following C++ Core Guidelines, February 15, 2024, "Don’t add redundant `==` or
`!=` to conditions",
http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#es87-dont-add-redundant--or--to-conditions

Modules/Core/Common/src/itkObjectFactoryBase.cxx

@@ -78,7 +78,7 @@ SynchronizeList(FactoryListType & output, FactoryListType & input, bool internal
     }
     if (pos == -1)
     {
-      if (internal == true)
+      if (internal)
       {
         itk::ObjectFactoryBase::RegisterFactoryInternal(factory);
       }

Modules/Core/Common/src/itkTBBMultiThreader.cxx

@@ -182,7 +182,7 @@ struct TBBImageRegionSplitter : public itk::ImageIORegion
   {
     // The following if statement is primarily used to ensure use of
     // is_splittable_in_proportion to avoid unused variable warning.
-    if (TBBImageRegionSplitter::is_splittable_in_proportion == true)
+    if (TBBImageRegionSplitter::is_splittable_in_proportion)
     {
       *this = region; // most things will be the same
       for (int d = static_cast<int>(this->GetImageDimension()) - 1; d >= 0;

Modules/Core/Common/test/itkBooleanStdVectorGTest.cxx

@@ -31,11 +31,11 @@ static_assert(
   ValueType{ false } == false,
   "The value type of BooleanStdVectorType should be allowed as a conditional expression, evaluating to false.");
 static_assert(
-  ValueType{ true } == true,
+  ValueType{ true },
   "The value type of BooleanStdVectorType should be allowed as a conditional expression, evaluating to true.");
 static_assert(bool{ ValueType{ false } } == false,
               "The value type of BooleanStdVectorType should support a lossless round-trip from bool value false.");
-static_assert(bool{ ValueType{ true } } == true,
+static_assert(bool{ ValueType{ true } },
               "The value type of BooleanStdVectorType should support a lossless round-trip from bool value true.");
 static_assert(std::is_same_v<decltype(*itk::BooleanStdVectorType{}.data()), ValueType &>,
               "BooleanStdVectorType should have a valid data() member function (unlike std::vector<bool>).");

Modules/Core/Common/test/itkMathTest.cxx

@@ -79,14 +79,14 @@ TestIntegersAreSame(const T1 & v1, const T2 & v2)
     std::cout << v2 << std::endl;
     testPassStatus = EXIT_FAILURE;
   }
-  if (itk::Math::AlmostEquals(v2, v1) == true)
+  if (itk::Math::AlmostEquals(v2, v1))
   {
     std::cout << "Error in "
               << "itk::Math::AlmostEquals(v2, v1) " << std::endl;
     std::cout << __FILE__ << ' ' << __LINE__ << ' ' << v2 << " == " << v1 << std::endl;
     testPassStatus = EXIT_FAILURE;
   }
-  if (itk::Math::AlmostEquals(v1, v2) == true)
+  if (itk::Math::AlmostEquals(v1, v2))
   {
     std::cout << "Error in "
               << "itk::Math::AlmostEquals(v1, v2) " << std::endl;
@@ -606,22 +606,21 @@ main(int, char *[])
     constexpr double d = 1.01;
 
     // Test AlmostEquals()
-    if (itk::Math::AlmostEquals(f, d) == true || itk::Math::AlmostEquals(d, f) == true)
+    if (itk::Math::AlmostEquals(f, d) || itk::Math::AlmostEquals(d, f))
     {
       std::cout << __FILE__ << ' ' << __LINE__ << ' ' << f << " == " << d << std::endl;
       testPassStatus = EXIT_FAILURE;
     }
     if (itk::Math::AlmostEquals(f, sc) == false || itk::Math::AlmostEquals(sc, f) == false ||
         itk::Math::AlmostEquals(1.0, 1.0f) == false || itk::Math::AlmostEquals(1.1, 1.1f) == false ||
-        itk::Math::AlmostEquals(1, 1.0) == false || itk::Math::AlmostEquals(2.0, 1.0) == true ||
-        itk::Math::AlmostEquals(1, 2) == true)
+        itk::Math::AlmostEquals(1, 1.0) == false || itk::Math::AlmostEquals(2.0, 1.0) || itk::Math::AlmostEquals(1, 2))
     {
       std::cout << __FILE__ << ' ' << __LINE__ << ' ' << f << " == " << d << std::endl;
       testPassStatus = EXIT_FAILURE;
     }
 
     // Test ExactlyEquals()  it should detect normal inequalities
-    if (itk::Math::ExactlyEquals(f, d) == true || itk::Math::ExactlyEquals(d, f) == true)
+    if (itk::Math::ExactlyEquals(f, d) || itk::Math::ExactlyEquals(d, f))
     {
       std::cout << __FILE__ << ' ' << __LINE__ << ' ' << f << " == " << d << std::endl;
       testPassStatus = EXIT_FAILURE;

Modules/Core/Common/test/itkMetaDataDictionaryTest.cxx

@@ -31,7 +31,7 @@ itkMetaDataDictionaryTest(int, char *[])
   {
     float      tempfloat = 0.0;
     const bool IsValidReturn = itk::ExposeMetaData<float>(MyDictionary, "ASimpleFloatInitalized", tempfloat);
-    if (IsValidReturn == true)
+    if (IsValidReturn)
     {
       std::cout << tempfloat << std::endl;
     }
@@ -158,7 +158,7 @@ itkMetaDataDictionaryTest(int, char *[])
     std::cerr << "Failed to erase ASimpleFloatChanged" << std::endl;
     return EXIT_FAILURE;
   }
-  if (MyDictionary.Erase("itk") == true)
+  if (MyDictionary.Erase("itk"))
   {
     std::cerr << "Failed erase itk" << std::endl;
     return EXIT_FAILURE;

Modules/Core/Common/test/itkMetaProgrammingLibraryTest.cxx

@@ -27,18 +27,18 @@ itkMetaProgrammingLibraryTest(int, char *[])
   using namespace itk::mpl;
 
   // Or between constants
-  static_assert(OrC<true, true, true>::Value == true, "Unit test failed");
-  static_assert(OrC<true, true, false>::Value == true, "Unit test failed");
-  static_assert(OrC<true, false, true>::Value == true, "Unit test failed");
-  static_assert(OrC<true, false, false>::Value == true, "Unit test failed");
-  static_assert(OrC<false, true, true>::Value == true, "Unit test failed");
-  static_assert(OrC<false, true, false>::Value == true, "Unit test failed");
-  static_assert(OrC<false, false, true>::Value == true, "Unit test failed");
+  static_assert(OrC<true, true, true>::Value, "Unit test failed");
+  static_assert(OrC<true, true, false>::Value, "Unit test failed");
+  static_assert(OrC<true, false, true>::Value, "Unit test failed");
+  static_assert(OrC<true, false, false>::Value, "Unit test failed");
+  static_assert(OrC<false, true, true>::Value, "Unit test failed");
+  static_assert(OrC<false, true, false>::Value, "Unit test failed");
+  static_assert(OrC<false, false, true>::Value, "Unit test failed");
   static_assert(OrC<false, false, false>::Value == false, "Unit test failed");
 
-  static_assert(OrC<true, true>::Value == true, "Unit test failed");
-  static_assert(OrC<true, false>::Value == true, "Unit test failed");
-  static_assert(OrC<false, true>::Value == true, "Unit test failed");
+  static_assert(OrC<true, true>::Value, "Unit test failed");
+  static_assert(OrC<true, false>::Value, "Unit test failed");
+  static_assert(OrC<false, true>::Value, "Unit test failed");
   static_assert(OrC<false, false>::Value == false, "Unit test failed");
 
   // Or between types
@@ -57,7 +57,7 @@ itkMetaProgrammingLibraryTest(int, char *[])
   static_assert(std::is_same_v<Or<FalseType, FalseType>::Type, FalseType>, "Unit test failed");
 
   // And between constants
-  static_assert(AndC<true, true>::Value == true, "Unit test failed");
+  static_assert(AndC<true, true>::Value, "Unit test failed");
   static_assert(AndC<true, false>::Value == false, "Unit test failed");
   static_assert(AndC<false, true>::Value == false, "Unit test failed");
   static_assert(AndC<false, false>::Value == false, "Unit test failed");
@@ -70,8 +70,8 @@ itkMetaProgrammingLibraryTest(int, char *[])
 
   // Xor between constants
   static_assert(XorC<true, true>::Value == false, "Unit test failed");
-  static_assert(XorC<true, false>::Value == true, "Unit test failed");
-  static_assert(XorC<false, true>::Value == true, "Unit test failed");
+  static_assert(XorC<true, false>::Value, "Unit test failed");
+  static_assert(XorC<false, true>::Value, "Unit test failed");
   static_assert(XorC<false, false>::Value == false, "Unit test failed");
 
   // Xor between types
@@ -82,7 +82,7 @@ itkMetaProgrammingLibraryTest(int, char *[])
 
   // Not between constants
   static_assert(NotC<true>::Value == false, "Unit test failed");
-  static_assert(NotC<false>::Value == true, "Unit test failed");
+  static_assert(NotC<false>::Value, "Unit test failed");
 
   // Not between types
   static_assert(std::is_same_v<Not<TrueType>::Type, FalseType>, "Unit test failed");

Modules/Core/Common/test/itkTimeStampTest.cxx

@@ -134,7 +134,7 @@ itkTimeStampTest(int, char *[])
           // been used
           const itk::ModifiedTimeType index = helper.timestamps[k].GetMTime() - min_mtime;
 
-          if (istimestamped[index] == true)
+          if (istimestamped[index])
           {
             iter_success = false;
             std::cerr << helper.timestamps[k].GetMTime() << " was used twice as a timestamp!" << std::endl;

Modules/Core/Common/test/itkXMLFileOutputWindowTest.cxx

@@ -134,5 +134,5 @@ itkXMLFileOutputWindowTest(int argc, char * argv[])
   const std::string test3Message{ status ? "TEST THREE PASSED" : "TEST THREE FAILED" };
   std::cout << test3Message << "\n\n" << std::endl;
 
-  return (status == true) ? EXIT_SUCCESS : EXIT_FAILURE;
+  return status ? EXIT_SUCCESS : EXIT_FAILURE;
 }

Modules/Core/FiniteDifference/include/itkFiniteDifferenceSparseImageFilter.hxx

@@ -145,7 +145,7 @@ template <typename TInputImageType, typename TSparseOutputImageType>
 auto
 FiniteDifferenceSparseImageFilter<TInputImageType, TSparseOutputImageType>::CalculateChange() -> TimeStepType
 {
-  if (m_PrecomputeFlag == true)
+  if (m_PrecomputeFlag)
   {
     this->PrecalculateChange();
   }

Modules/Core/ImageFunction/include/itkGaussianBlurImageFunction.hxx

@@ -187,7 +187,7 @@ GaussianBlurImageFunction<TInputImage, TOutput>::RecomputeGaussianKernel()
     gaussianOperator.SetMaximumError(m_MaximumError[direction]);
     gaussianOperator.SetMaximumKernelWidth(m_MaximumKernelWidth);
 
-    if ((m_UseImageSpacing == true) && (this->GetInputImage()))
+    if (m_UseImageSpacing && (this->GetInputImage()))
     {
       if (this->GetInputImage()->GetSpacing()[direction] == 0.0)
       {
@@ -371,7 +371,7 @@ GaussianBlurImageFunction<TInputImage, TOutput>::RecomputeContinuousGaussianKern
     {
       typename GaussianFunctionType::InputType pt;
       pt[0] = gaussianNeighborhood.GetOffset(i)[direction] - offset[direction];
-      if ((m_UseImageSpacing == true) && (this->GetInputImage()))
+      if (m_UseImageSpacing && (this->GetInputImage()))
       {
         if (this->GetInputImage()->GetSpacing()[direction] == 0.0)
         {

Modules/Core/QuadEdgeMesh/include/itkQuadEdgeMeshEulerOperatorJoinVertexFunction.hxx

@@ -235,7 +235,7 @@ template <typename TMesh, typename TQEType>
 TQEType *
 QuadEdgeMeshEulerOperatorJoinVertexFunction<TMesh, TQEType>::ProcessIsolatedQuadEdge(QEType * e)
 {
-  QEType * temp = (e->IsIsolated() == true) ? e->GetSym() : e;
+  QEType * temp = (e->IsIsolated()) ? e->GetSym() : e;
   QEType * rebuildEdge = temp->GetOprev();
 
   m_OldPointID = temp->GetSym()->GetOrigin();
@@ -296,7 +296,7 @@ QuadEdgeMeshEulerOperatorJoinVertexFunction<TMesh, TQEType>::IsFaceIsolated(QETy
   // turn around the face (left or right one) while edges are on the border
   // and push them into a stack (which will be used to delete properly all
   // elements )
-  QEType * temp = (iWasLeftFace == true) ? e : e_sym;
+  QEType * temp = iWasLeftFace ? e : e_sym;
   QEType * e_it = temp;
 
   oToBeDeleted.push(e_it);

Modules/Core/QuadEdgeMesh/test/itkQuadEdgeTest1.cxx

@@ -1236,7 +1236,7 @@ itkQuadEdgeTest1(int, char *[])
     quadEdge1->SetOnext(nullptr);
     quadEdge1c->IsEdgeInOnextRing(nullptr);
 
-    if (quadEdge1c->IsEdgeInOnextRing(quadEdge6) == true)
+    if (quadEdge1c->IsEdgeInOnextRing(quadEdge6))
     {
       std::cerr << "Error in IsEdgeInOnextRing() A" << std::endl;
       return EXIT_FAILURE;
@@ -1249,7 +1249,7 @@ itkQuadEdgeTest1(int, char *[])
     quadEdge4->SetOnext(quadEdge5);
     quadEdge5->SetOnext(quadEdge1);
 
-    if (quadEdge1c->IsEdgeInOnextRing(quadEdge6) == true)
+    if (quadEdge1c->IsEdgeInOnextRing(quadEdge6))
     {
       std::cerr << "Error in IsEdgeInOnextRing() B" << std::endl;
       return EXIT_FAILURE;
@@ -1327,7 +1327,7 @@ itkQuadEdgeTest1(int, char *[])
 #ifndef NDEBUG
     quadEdgeA1c->IsLnextGivenSizeCyclic(3); // testing null case
 
-    if (quadEdgeA1c->IsLnextGivenSizeCyclic(3) == true)
+    if (quadEdgeA1c->IsLnextGivenSizeCyclic(3))
     {
       std::cerr << "Error in IsLnextGivenSizeCyclic() A" << std::endl;
       return EXIT_FAILURE;
@@ -1425,7 +1425,7 @@ itkQuadEdgeTest1(int, char *[])
     }
 
     // Check a wrong period on purpose
-    if (quadEdgeA1c->IsLnextGivenSizeCyclic(4) == true)
+    if (quadEdgeA1c->IsLnextGivenSizeCyclic(4))
     {
       std::cerr << "Error in IsLnextGivenSizeCyclic() C" << std::endl;
       return EXIT_FAILURE;

Modules/Core/Transform/include/itkBSplineTransformInitializer.hxx

@@ -238,7 +238,7 @@ BSplineTransformInitializer<TTransform, TImage>::InitializeTransform() const
   this->m_Transform->SetTransformDomainOrigin(transformDomainOrigin);
   this->m_Transform->SetTransformDomainPhysicalDimensions(transformDomainPhysicalDimensions);
   this->m_Transform->SetTransformDomainDirection(transformDomainDirection);
-  if (this->m_SetTransformDomainMeshSizeViaInitializer == true)
+  if (this->m_SetTransformDomainMeshSizeViaInitializer)
   {
     this->m_Transform->SetTransformDomainMeshSize(this->m_TransformDomainMeshSize);
   }
@@ -254,7 +254,7 @@ BSplineTransformInitializer<TTransform, TImage>::PrintSelf(std::ostream & os, In
 
   itkPrintSelfObjectMacro(Transform);
 
-  if (this->m_SetTransformDomainMeshSizeViaInitializer == true)
+  if (this->m_SetTransformDomainMeshSizeViaInitializer)
   {
     os << indent << "Transform domain mesh size: " << this->m_TransformDomainMeshSize << std::endl;
   }

Modules/Core/Transform/test/itkSplineKernelTransformTest.cxx

@@ -193,7 +193,7 @@ itkSplineKernelTransformTest(int, char *[])
     source2Dit++;
     target2Dit++;
   }
-  if (tps2D->IsLinear() == true) // NOTE TPS is never linear!
+  if (tps2D->IsLinear()) // NOTE TPS is never linear!
   {
     std::cout << "ERROR:  2D TPS reports as being a linear transform." << std::endl;
     return EXIT_FAILURE;

Modules/Filtering/Colormap/include/itkScalarToRGBColormapImageFilter.hxx

@@ -68,7 +68,7 @@ template <typename TInputImage, typename TOutputImage>
 void
 ScalarToRGBColormapImageFilter<TInputImage, TOutputImage>::BeforeThreadedGenerateData()
 {
-  if (this->m_UseInputImageExtremaForScaling == true)
+  if (this->m_UseInputImageExtremaForScaling)
   {
     ImageRegionConstIterator<InputImageType> It(this->GetInput(), this->GetInput()->GetRequestedRegion());
 

Modules/Filtering/DisplacementField/include/itkDisplacementFieldJacobianDeterminantFilter.hxx

@@ -76,7 +76,7 @@ DisplacementFieldJacobianDeterminantFilter<TInputImage, TRealType, TOutputImage>
 
   // Only reset the weights if they were previously set to the image spacing,
   // otherwise, the user may have provided their own weightings.
-  if (f == false && m_UseImageSpacing == true)
+  if (f == false && m_UseImageSpacing)
   {
     for (unsigned int i = 0; i < ImageDimension; ++i)
     {
@@ -145,7 +145,7 @@ DisplacementFieldJacobianDeterminantFilter<TInputImage, TRealType, TOutputImage>
   // Set the weights on the derivatives.
   // Are we using image spacing in the calculations?  If so we must update now
   // in case our input image has changed.
-  if (m_UseImageSpacing == true)
+  if (m_UseImageSpacing)
   {
     for (unsigned int i = 0; i < ImageDimension; ++i)
     {

Modules/Filtering/DistanceMap/test/itkSignedDanielssonDistanceMapImageFilterTest11.cxx

@@ -131,7 +131,7 @@ itkSignedDanielssonDistanceMapImageFilterTest11(int, char *[])
     return EXIT_FAILURE;
   }
 
-  if (filter2D->GetSquaredDistance() == true)
+  if (filter2D->GetSquaredDistance())
   {
     std::cerr << "filter2D->GetSquaredDistance() == true & it should not" << std::endl;
     return EXIT_FAILURE;

Modules/Filtering/DistanceMap/test/itkSignedMaurerDistanceMapImageFilterTest11.cxx

@@ -137,7 +137,7 @@ itkSignedMaurerDistanceMapImageFilterTest11(int, char *[])
     return EXIT_FAILURE;
   }
 
-  if (filter2D->GetSquaredDistance() == true)
+  if (filter2D->GetSquaredDistance())
   {
     std::cerr << "filter2D->GetSquaredDistance() == true and it should not be" << std::endl;
     return EXIT_FAILURE;

Modules/Filtering/FFT/src/itkFFTWGlobalConfiguration.cxx

@@ -779,7 +779,7 @@ FFTWGlobalConfiguration::SetReadWisdomCache(const bool v)
 {
   itkInitGlobalsMacro(PimplGlobals);
   GetInstance()->m_ReadWisdomCache = v;
-  if (v == true)
+  if (v)
   {
     ImportDefaultWisdomFile();
   }

Modules/Filtering/GPUSmoothing/include/itkGPUDiscreteGaussianImageFilter.hxx

@@ -166,7 +166,7 @@ GPUDiscreteGaussianImageFilter<TInputImage, TOutputImage>::GPUGenerateData()
 
     // Set up the operator for this dimension
     oper[reverse_i].SetDirection(i);
-    if (this->GetUseImageSpacing() == true)
+    if (this->GetUseImageSpacing())
     {
       if (localInput->GetSpacing()[i] == 0.0)
       {

Modules/Filtering/ImageCompare/include/itkSTAPLEImageFilter.hxx

@@ -244,7 +244,7 @@ STAPLEImageFilter<TInputImage, TOutputImage>::GenerateData()
       flag = true;
     }
 
-    if (flag == true)
+    if (flag)
     {
       break;
     }

Modules/Filtering/ImageFeature/include/itkDerivativeImageFilter.hxx

@@ -95,7 +95,7 @@ DerivativeImageFilter<TInputImage, TOutputImage>::GenerateData()
   oper.CreateDirectional();
   oper.FlipAxes();
 
-  if (m_UseImageSpacing == true)
+  if (m_UseImageSpacing)
   {
     if (this->GetInput()->GetSpacing()[m_Direction] == 0.0)
     {

Modules/Filtering/ImageFeature/include/itkDiscreteGaussianDerivativeImageFilter.hxx

@@ -51,7 +51,7 @@ DiscreteGaussianDerivativeImageFilter<TInputImage, TOutputImage>::GenerateInputR
     // Determine the size of the operator in this dimension.  Note that the
     // Gaussian is built as a 1D operator in each of the specified directions.
     oper.SetDirection(i);
-    if (m_UseImageSpacing == true)
+    if (m_UseImageSpacing)
     {
       oper.SetSpacing(this->GetInput()->GetSpacing()[i]);
     }
@@ -157,7 +157,7 @@ DiscreteGaussianDerivativeImageFilter<TInputImage, TOutputImage>::GenerateData()
     // Set up the operator for this dimension
     oper[reverse_i].SetDirection(i);
     oper[reverse_i].SetOrder(m_Order[i]);
-    if (m_UseImageSpacing == true)
+    if (m_UseImageSpacing)
     {
       // convert the variance from physical units to pixels
       double s = localInput->GetSpacing()[i];

Modules/Filtering/ImageFrequency/test/itkFrequencyFFTLayoutImageRegionIteratorWithIndexTest.cxx

@@ -163,7 +163,7 @@ class itkFrequencyFFTLayoutImageRegionIteratorWithIndexTester
       if (it.GetIndex() == firstNegativeIndex)
       {
         // abs value should be equal to largest freq for odd images
-        if (m_ImageIsOdd == true && m_LargestFrequency != it.GetFrequency() && -m_LargestFrequency != it.GetFrequency())
+        if (m_ImageIsOdd && m_LargestFrequency != it.GetFrequency() && -m_LargestFrequency != it.GetFrequency())
         {
           std::cout << " Frequency value is wrong." << it.GetFrequency() << " should be: " << m_LargestFrequency
                     << std::endl;

Modules/Filtering/ImageFusion/include/itkScalarToRGBPixelFunctor.hxx

@@ -50,7 +50,7 @@ ScalarToRGBPixelFunctor<TScalar>::operator()(const TScalar & v) const -> RGBPixe
   TScalar      buf = v;
   const auto * bytes = reinterpret_cast<const unsigned char *>(&buf);
 
-  if (this->m_UseMSBForHashing == true)
+  if (this->m_UseMSBForHashing)
   { // swap bytes
     // always swap regardless of system endianness
     if (ByteSwapper<TScalar>::SystemIsBigEndian())