STYLE: Prefer C++11 type alias over typedef

== http://en.cppreference.com/w/cpp/language/type_alias ==

Type alias is a name that refers to a previously defined type (similar
to typedef).

A type alias declaration introduces a name which can be used as a
synonym for the type denoted by type-id. It does not introduce a new
type and it cannot change the meaning of an existing type name. There is
no difference between a type alias declaration and typedef declaration.
This declaration may appear in block scope, class scope, or namespace
scope.

== https://www.quora.com/Is-using-typedef-in-C++-considered-a-bad-practice ==

While typedef is still available for backward compatibility, the new
Type Alias syntax 'using Alias = ExistingLongName;' is more consistent
with the flow of C++ than the old typedef syntax 'typedef
ExistingLongName Alias;', and it also works for templates (Type alias,
alias template (since C++11)), so leftover 'typedef' aliases will differ
in style from any alias templates.

Broken/EdgesAndGradients/CannyEdgeDetectionImageFilter.cxx

@@ -32,14 +32,13 @@ int main(int argc, char *argv[])
     upperThreshold = atof(argv[4]);
     }
 
-  typedef itk::Image<double, 2>  DoubleImageType;
+  using DoubleImageType = itk::Image<double, 2>;
 
-  typedef itk::ImageFileReader<DoubleImageType> ReaderType;
+  using ReaderType = itk::ImageFileReader<DoubleImageType>;
   ReaderType::Pointer reader = ReaderType::New();
   reader->SetFileName(argv[1]);
 
-  typedef itk::CannyEdgeDetectionImageFilter <DoubleImageType, DoubleImageType>
-    CannyEdgeDetectionImageFilterType;
+  using CannyEdgeDetectionImageFilterType = itk::CannyEdgeDetectionImageFilter <DoubleImageType, DoubleImageType>;
 
   CannyEdgeDetectionImageFilterType::Pointer cannyFilter
     = CannyEdgeDetectionImageFilterType::New();

Broken/Functions/GaussianBlurImageFunctionFilter.cxx

@@ -29,10 +29,10 @@ int main( int argc, char * argv[] )
   ss >> maxKernelWidth;
   }
 
-  typedef itk::Image< float, 2 >             ImageType;
-  typedef itk::ImageFileReader< ImageType >  ReaderType;
-  typedef itk::ImageRegionIterator< ImageType > IteratorType;
-  typedef itk::ImageRegionConstIterator< ImageType > ConstIteratorType;
+  using ImageType = itk::Image< float, 2 >;
+  using ReaderType = itk::ImageFileReader< ImageType >;
+  using IteratorType = itk::ImageRegionIterator< ImageType >;
+  using ConstIteratorType = itk::ImageRegionConstIterator< ImageType >;
 
   ReaderType::Pointer reader = ReaderType::New();
   reader->SetFileName( inputFileName );
@@ -65,16 +65,16 @@ int main( int argc, char * argv[] )
     }
   */
 
-  typedef itk::GaussianBlurImageFunction< ImageType > GaussianBlurImageFunctionType;
+  using GaussianBlurImageFunctionType = itk::GaussianBlurImageFunction< ImageType >;
   // SetFunctor seems to need an actual object (not a pointer), but we can't create one like this:
   //GaussianBlurImageFunctionType gaussianFunction;
 
   GaussianBlurImageFunctionType::Pointer gaussianFunction = GaussianBlurImageFunctionType::New();
   //gaussianFunction->SetInputImage( reader->GetOutput() ); // Do we need to do this since we are going to do unaryFunctor->SetInput?
 
 
-  typedef itk::UnaryFunctorImageFilter<ImageType,ImageType,
-                                  GaussianBlurImageFunctionType> FilterType;
+  using FilterType = itk::UnaryFunctorImageFilter<ImageType,ImageType,
+                                  GaussianBlurImageFunctionType>;
   FilterType::Pointer filter = FilterType::New();
   filter->SetInput(reader->GetOutput());
 
@@ -86,7 +86,7 @@ int main( int argc, char * argv[] )
 
   filter->Update();
 
-  typedef itk::ImageFileWriter < ImageType > WriterType;
+  using WriterType = itk::ImageFileWriter < ImageType >;
   WriterType::Pointer writer = WriterType::New();
   writer->SetFileName(outputFileName);
   writer->SetInput(filter->GetOutput());

Broken/ImageProcessing/GradientOfVectorImage.cxx

@@ -6,8 +6,8 @@
 int main(int argc, char * argv[])
 {
   // Setup types
-  typedef itk::CovariantVector<float, 2> VectorType;
-  typedef itk::Image<VectorType, 2>   VectorImageType;
+  using VectorType = itk::CovariantVector<float, 2>;
+  using VectorImageType = itk::Image<VectorType, 2>;
   VectorImageType::Pointer image = VectorImageType::New();
 
   itk::Size<2> size;
@@ -32,8 +32,8 @@ int main(int argc, char * argv[])
     }
 
   // Create and setup a gradient filter
-  typedef itk::GradientImageFilter<
-      VectorImageType, VectorType>  GradientFilterType;
+  using GradientFilterType = itk::GradientImageFilter<
+      VectorImageType, VectorType>;
   GradientFilterType::Pointer gradientFilter = GradientFilterType::New();
   gradientFilter->SetInput(image);
   gradientFilter->Update();

Broken/ImageProcessing/MutualInformationImageToImageFilter.cxx

@@ -3,8 +3,8 @@
 #include "itkTranslationTransform.h"
 #include "itkLinearInterpolateImageFunction.h"
 
-//typedef itk::Image< unsigned char, 2>  ImageType;
-typedef itk::Image< float, 2> ImageType;
+//using ImageType = itk::Image< unsigned char, 2>;
+using ImageType = itk::Image< float, 2>;
 
 int main( int argc, char *argv[] )
 {
@@ -30,10 +30,10 @@ int main( int argc, char *argv[] )
   //ImageType::Pointer movingImage = randomImageSource2->GetOutput();
   ImageType::Pointer movingImage = randomImageSource1->GetOutput();
 
-  typedef itk::TranslationTransform<double, 2> TranslationTransformType; // This cannot be float for some reason?
+  using TranslationTransformType = itk::TranslationTransform<double, 2>; // This cannot be float for some reason?
   TranslationTransformType::Pointer transform = TranslationTransformType::New();
 
-  typedef itk::MutualInformationImageToImageMetric<ImageType, ImageType >    MetricType;
+  using MetricType = itk::MutualInformationImageToImageMetric<ImageType, ImageType >;
 
   MetricType::Pointer metric = MetricType::New();
 

Broken/Images/ConnectedThresholdImageFilter.cxx

@@ -12,7 +12,7 @@
 #include "vtkInteractorStyleImage.h"
 #include "vtkRenderer.h"
 
-typedef itk::Image< PixelType, Dimension >  ImageType;
+using ImageType = itk::Image< PixelType, Dimension >;
 
 static void CreateImage(ImageType::Pointer image);
 
@@ -21,7 +21,7 @@ int main( int argc, char *argv[])
   ImageType::Pointer image = ImageType::New();
   CreateImage(image);
 
-  typedef itk::ConnectedThresholdImageFilter<ImageType, ImageType> ConnectedFilterType;
+  using ConnectedFilterType = itk::ConnectedThresholdImageFilter<ImageType, ImageType>;
   ConnectedFilterType::Pointer connectedThreshold = ConnectedFilterType::New();
   float lower = 95.0;
   float upper = 105.0;
@@ -47,7 +47,7 @@ int main( int argc, char *argv[])
   connectedThreshold->SetInput(image);
 
   // Visualize
-  typedef itk::ImageToVTKImageFilter<ImageType> ConnectorType;
+  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
   ConnectorType::Pointer connector2 = ConnectorType::New();
   connector2->SetInput(image2);
 

Broken/Images/GradientImageFilter.cxx

@@ -35,23 +35,23 @@ int main(int argc, char * argv[])
   std::string inputFilename = argv[1];
 
   // Setup types
-  typedef itk::Image< float,  2 >   FloatImageType;
-  typedef itk::Image< unsigned char, 2 >   UnsignedCharImageType;
+  using FloatImageType = itk::Image< float,  2 >;
+  using UnsignedCharImageType = itk::Image< unsigned char, 2 >;
 
   // Create and setup a reader
-  typedef itk::ImageFileReader< UnsignedCharImageType >  ReaderType;
+  using ReaderType = itk::ImageFileReader< UnsignedCharImageType >;
   ReaderType::Pointer reader = ReaderType::New();
   reader->SetFileName( inputFilename.c_str() );
 
   // Create and setup a gradient filter
-  typedef itk::GradientImageFilter<
-      UnsignedCharImageType, float>  GradientFilterType;
+  using GradientFilterType = itk::GradientImageFilter<
+      UnsignedCharImageType, float>;
   GradientFilterType::Pointer gradientFilter = GradientFilterType::New();
   gradientFilter->SetInput( reader->GetOutput() );
   gradientFilter->Update();
 
   // Visualize original image
-  typedef itk::ImageToVTKImageFilter<UnsignedCharImageType> ConnectorType;
+  using ConnectorType = itk::ImageToVTKImageFilter<UnsignedCharImageType>;
   ConnectorType::Pointer originalConnector = ConnectorType::New();
   originalConnector->SetInput(reader->GetOutput());
 

Broken/Images/InPlace.cxx

@@ -11,7 +11,7 @@
 #include "vtkInteractorStyleImage.h"
 #include "vtkRenderer.h"
 
-typedef itk::Image< unsigned char, 2 >  ImageType;
+using ImageType = itk::Image< unsigned char, 2 >;
 
 static void ApplyThresholding(ImageType::Pointer image);
 
@@ -25,7 +25,7 @@ int main(int argc, char *argv[])
 
   std::string inputFilename = argv[1];
 
-  typedef itk::ImageFileReader<ImageType> ReaderType;
+  using ReaderType = itk::ImageFileReader<ImageType>;
   ReaderType::Pointer reader = ReaderType::New();
 
   reader->SetFileName(inputFilename.c_str());
@@ -36,7 +36,7 @@ int main(int argc, char *argv[])
   ApplyThresholding(image);
 
   // Visualize
-  typedef itk::ImageToVTKImageFilter<ImageType> ConnectorType;
+  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
   ConnectorType::Pointer connector = ConnectorType::New();
   connector->SetInput(image);
 
@@ -74,8 +74,7 @@ int main(int argc, char *argv[])
 void ApplyThresholding(ImageType::Pointer image)
 {
 
-  typedef itk::BinaryThresholdImageFilter <ImageType, ImageType>
-          BinaryThresholdImageFilterType;
+  using BinaryThresholdImageFilterType = itk::BinaryThresholdImageFilter <ImageType, ImageType>;
 
   BinaryThresholdImageFilterType::Pointer thresholdFilter
           = BinaryThresholdImageFilterType::New();

Broken/Images/NormalizedCorrelationImageFilterMasked.cxx

@@ -12,9 +12,9 @@
 #include <iostream>
 #include <string>
 
-typedef itk::Image<unsigned char, 2> ImageType;
-typedef itk::Image<unsigned char, 2> MaskType;
-typedef itk::Image<float, 2> FloatImageType;
+using ImageType = itk::Image<unsigned char, 2>;
+using MaskType = itk::Image<unsigned char, 2>;
+using FloatImageType = itk::Image<float, 2>;
 
 void CreateMask(MaskType* const mask);
 void CreateImage(ImageType* const image);
@@ -71,7 +71,7 @@ int main(int argc, char *argv[])
 
   // Perform normalized correlation
   // <input type, mask type, output type>
-  typedef itk::NormalizedCorrelationImageFilter<ImageType, MaskType, FloatImageType, unsigned char> CorrelationFilterType;
+  using CorrelationFilterType = itk::NormalizedCorrelationImageFilter<ImageType, MaskType, FloatImageType, unsigned char>;
   CorrelationFilterType::Pointer correlationFilter = CorrelationFilterType::New();
   correlationFilter->SetInput(image2);
   correlationFilter->SetMaskImage(mask);
@@ -80,15 +80,15 @@ int main(int argc, char *argv[])
 
   WriteImage(correlationFilter->GetOutput(), "correlation.mha");
 
-  typedef itk::RescaleIntensityImageFilter<FloatImageType, ImageType> RescaleFilterType;
+  using RescaleFilterType = itk::RescaleIntensityImageFilter<FloatImageType, ImageType>;
   RescaleFilterType::Pointer rescaleFilter = RescaleFilterType::New();
   rescaleFilter->SetInput(correlationFilter->GetOutput());
   rescaleFilter->SetOutputMinimum(0);
   rescaleFilter->SetOutputMaximum(255);
   rescaleFilter->Update();
   WriteImage(rescaleFilter->GetOutput(), "correlation.png");
 
-  typedef itk::MinimumMaximumImageCalculator<FloatImageType> MinimumMaximumImageCalculatorType;
+  using MinimumMaximumImageCalculatorType = itk::MinimumMaximumImageCalculator<FloatImageType>;
   MinimumMaximumImageCalculatorType::Pointer minimumMaximumImageCalculatorFilter = MinimumMaximumImageCalculatorType::New ();
   minimumMaximumImageCalculatorFilter->SetImage(correlationFilter->GetOutput());
   minimumMaximumImageCalculatorFilter->Compute();
@@ -190,7 +190,7 @@ void CreateImageOfSquare(ImageType* const image, const itk::Index<2>& cornerOfSq
 template <typename TImage>
 void WriteImage(const TImage* const image, const std::string& filename)
 {
-  typedef  itk::ImageFileWriter<TImage> WriterType;
+  using WriterType = itk::ImageFileWriter<TImage>;
   typename WriterType::Pointer writer = WriterType::New();
   writer->SetFileName(filename);
   writer->SetInput(image);

Broken/Images/RegionGrowImageFilter.cxx

@@ -12,7 +12,7 @@
 #include "vtkInteractorStyleImage.h"
 #include "vtkRenderer.h"
 
-typedef itk::Image< PixelType, Dimension >  ImageType;
+using ImageType = itk::Image< PixelType, Dimension >;
 
 static void CreateImage(ImageType::Pointer image);
 
@@ -21,7 +21,7 @@ int main( int argc, char *argv[])
   ImageType::Pointer image = ImageType::New();
   CreateImage(image);
 
-  typedef itk::RegionGrowImageFilter<ImageType, ImageType> RegionGrowImageFilterType;
+  using RegionGrowImageFilterType = itk::RegionGrowImageFilter<ImageType, ImageType>;
   RegionGrowImageFilterType::Pointer regionGrow = RegionGrowImageFilterType::New();
   float lower = 95.0;
   float upper = 105.0;
@@ -47,7 +47,7 @@ int main( int argc, char *argv[])
   regionGrow->SetInput(image);
 
   // Visualize
-  typedef itk::ImageToVTKImageFilter<ImageType> ConnectorType;
+  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
   ConnectorType::Pointer connector2 = ConnectorType::New();
   connector2->SetInput(image2);
 

Broken/Images/VTKImageToImageFilter.cxx

@@ -29,9 +29,9 @@ int main(int argc, char*argv[])
   luminanceFilter->SetInputConnection(reader->GetOutputPort());
   luminanceFilter->Update();
 
-  typedef itk::Image<unsigned char, 2> ImageType;
+  using ImageType = itk::Image<unsigned char, 2>;
 
-  typedef itk::VTKImageToImageFilter<ImageType> VTKImageToImageType;
+  using VTKImageToImageType = itk::VTKImageToImageFilter<ImageType>;
 
   VTKImageToImageType::Pointer vtkImageToImageFilter = VTKImageToImageType::New();
   vtkImageToImageFilter->SetInput(luminanceFilter->GetOutput());

Broken/SimpleOperations/MetaDataDictionary.cxx

@@ -5,7 +5,7 @@
 #include <itkImageFileWriter.h>
 #include <itkImageFileReader.h>
 
-typedef itk::Image<unsigned char, 2> ImageType;
+using ImageType = itk::Image<unsigned char, 2>;
 
 static void CreateImage(ImageType::Pointer image);
 
@@ -36,14 +36,14 @@ int main(int, char*[])
     }
 
   // Write the image (and the data) to a file
-  typedef  itk::ImageFileWriter< ImageType  > WriterType;
+  using WriterType = itk::ImageFileWriter< ImageType  >;
   WriterType::Pointer writer = WriterType::New();
   writer->SetFileName("test.mhd");
   writer->SetInput(image);
   writer->Update();
 
   // Read the image (and data) from the file
-  typedef itk::ImageFileReader<ImageType> ReaderType;
+  using ReaderType = itk::ImageFileReader<ImageType>;
   ReaderType::Pointer reader = ReaderType::New();
   reader->SetFileName("test.mhd");
 

Broken/Statistics/ExpectationMaximizationMixtureModelEstimator_1D.cxx

@@ -7,11 +7,11 @@
 int main(int, char*[])
 {
   unsigned int numberOfClasses = 2;
-  typedef itk::Vector< double, 1 > MeasurementVectorType;
-  typedef itk::Statistics::ListSample< MeasurementVectorType > SampleType;
+  using MeasurementVectorType = itk::Vector< double, 1 >;
+  using SampleType = itk::Statistics::ListSample< MeasurementVectorType >;
   SampleType::Pointer sample = SampleType::New();
 
-  typedef itk::Statistics::NormalVariateGenerator NormalGeneratorType;
+  using NormalGeneratorType = itk::Statistics::NormalVariateGenerator;
   NormalGeneratorType::Pointer normalGenerator = NormalGeneratorType::New();
 
   normalGenerator->Initialize(101);
@@ -36,7 +36,7 @@ int main(int, char*[])
     sample->PushBack( mv );
     }
 
-  typedef itk::Array< double > ParametersType;
+  using ParametersType = itk::Array< double >;
   ParametersType params1( 2 );
 
   std::vector< ParametersType > initialParameters( numberOfClasses );
@@ -49,18 +49,18 @@ int main(int, char*[])
   params2[1] = 50.0;
   initialParameters[1] = params2;
 
-  typedef itk::Statistics::GaussianMixtureModelComponent< SampleType > ComponentType;
+  using ComponentType = itk::Statistics::GaussianMixtureModelComponent< SampleType >;
 
   std::vector< ComponentType::Pointer > components;
-  for ( unsigned int i = 0 ; i < numberOfClasses ; i++ )
+  for ( unsigned int i = 0; i < numberOfClasses; i++ )
     {
     components.push_back( ComponentType::New() );
     components[i]->SetSample( sample );
     components[i]->SetParameters( initialParameters[i] );
     }
 
-  typedef itk::Statistics::ExpectationMaximizationMixtureModelEstimator<
-                           SampleType > EstimatorType;
+  using EstimatorType = itk::Statistics::ExpectationMaximizationMixtureModelEstimator<
+                           SampleType >;
   EstimatorType::Pointer estimator = EstimatorType::New();
 
   estimator->SetSample(sample);