ITK  5.2.0
Insight Toolkit
Examples/DataRepresentation/Image/ImageAdaptor3.cxx
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* Licensed under the Apache License, Version 2.0 (the "License");
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// Software Guide : BeginLatex
//
// This example illustrates the use of \doxygen{ImageAdaptor}
// to obtain access to the components of a vector image.
// Specifically, it shows how to manage pixel accessors containing
// internal parameters. In this example we create an image of vectors by using
// a gradient filter. Then, we use an image adaptor to extract one of the
// components of the vector image. The vector type used by the gradient filter
// is the \doxygen{CovariantVector} class.
//
// We start by including the relevant headers.
//
// \index{itk::ImageAdaptor!Instantiation}
// \index{itk::ImageAdaptor!Header}
// \index{itk::PixelAccessor!with parameters}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// A pixel accessors class may have internal parameters that affect the
// operations performed on input pixel data. Image adaptors support
// parameters in their internal pixel accessor by using
// the assignment operator. Any pixel accessor which has internal
// parameters must therefore implement the assignment operator.
// The following defines a pixel accessor for extracting
// components from a vector pixel. The
// \code{m\_Index} member variable is used to select the vector component
// to be returned.
//
// Software Guide : EndLatex
namespace itk
{
// Software Guide : BeginCodeSnippet
class VectorPixelAccessor
{
public:
using InternalType = itk::CovariantVector<float, 2>;
using ExternalType = float;
VectorPixelAccessor() = default;
VectorPixelAccessor &
operator=(const VectorPixelAccessor & vpa) = default;
ExternalType
Get(const InternalType & input) const
{
return static_cast<ExternalType>(input[m_Index]);
}
void
SetIndex(unsigned int index)
{
m_Index = index;
}
private:
unsigned int m_Index{ 0 };
};
// Software Guide : EndCodeSnippet
} // namespace itk
// Software Guide : BeginLatex
//
// The \code{Get()} method simply returns the \emph{i}-th component of
// the vector as indicated by the index. The assignment operator transfers
// the value of the index member variable from one instance of the pixel
// accessor to another.
//
// Software Guide : EndLatex
//-------------------------
//
// Main code
//
//-------------------------
int
main(int argc, char * argv[])
{
if (argc < 4)
{
std::cerr << "Usage: " << std::endl;
std::cerr << "ImageAdaptor3 inputFileName outputComponentFileName ";
std::cerr << " indexOfComponentToExtract" << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// In order to test the pixel accessor, we generate an image of vectors
// using the \doxygen{GradientRecursiveGaussianImageFilter}. This filter
// produces an output image of \doxygen{CovariantVector} pixel type.
// Covariant vectors are the natural representation for gradients since
// they are the equivalent of normals to iso-values manifolds.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using InputPixelType = unsigned char;
constexpr unsigned int Dimension = 2;
using InputImageType = itk::Image<InputPixelType, Dimension>;
using VectorPixelType = itk::CovariantVector<float, Dimension>;
using VectorImageType = itk::Image<VectorPixelType, Dimension>;
using GradientFilterType =
VectorImageType>;
GradientFilterType::Pointer gradient = GradientFilterType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We instantiate the ImageAdaptor using the vector image type as
// the first template parameter and the pixel accessor as the second
// template parameter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using ImageAdaptorType =
ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The index of the component to be extracted is specified
// from the command line. In the following, we create the accessor,
// set the index and connect the accessor to the image adaptor using
// the \code{SetPixelAccessor()} method.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
itk::VectorPixelAccessor accessor;
accessor.SetIndex(std::stoi(argv[3]));
adaptor->SetPixelAccessor(accessor);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We create a reader to load the image specified from the
// command line and pass its output as the input to the gradient filter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ReaderType::Pointer reader = ReaderType::New();
gradient->SetInput(reader->GetOutput());
reader->SetFileName(argv[1]);
gradient->Update();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We now connect the output of the gradient filter as input to the
// image adaptor. The adaptor emulates a scalar image whose pixel values
// are taken from the selected component of the vector image.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
adaptor->SetImage(gradient->GetOutput());
// Software Guide : EndCodeSnippet
using OutputImageType = itk::Image<unsigned char, Dimension>;
using RescalerType =
RescalerType::Pointer rescaler = RescalerType::New();
WriterType::Pointer writer = WriterType::New();
writer->SetFileName(argv[2]);
rescaler->SetOutputMinimum(0);
rescaler->SetOutputMaximum(255);
rescaler->SetInput(adaptor);
writer->SetInput(rescaler->GetOutput());
writer->Update();
// Software Guide : BeginLatex
//
// \begin{figure} \center
// \includegraphics[width=0.32\textwidth]{BrainProtonDensitySlice}
// \includegraphics[width=0.32\textwidth]{ImageAdaptorToVectorImageComponentX}
// \includegraphics[width=0.32\textwidth]{ImageAdaptorToVectorImageComponentY}
// \itkcaption[Image Adaptor to Vector Image]{Using
// ImageAdaptor to access components of a vector
// image. The input image on the left was passed through a gradient image
// filter and the two components of the resulting vector image were
// extracted using an image adaptor.} \label{fig:ImageAdaptorToVectorImage}
// \end{figure}
//
// As in the previous example, we rescale the scalar image before writing
// the image out to file. Figure~\ref{fig:ImageAdaptorToVectorImage}
// shows the result of applying the example code for extracting both
// components of a two dimensional gradient.
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}
itkImageFileReader.h
itkImageAdaptor.h
itkImageRegionIteratorWithIndex.h
itk::ImageAdaptor
Give access to partial aspects of voxels from an Image.
Definition: itkImageAdaptor.h:56
itk::ImageFileReader
Data source that reads image data from a single file.
Definition: itkImageFileReader.h:75
itkGradientRecursiveGaussianImageFilter.h
itk::ImageFileWriter
Writes image data to a single file.
Definition: itkImageFileWriter.h:87
itk::GradientRecursiveGaussianImageFilter
Computes the gradient of an image by convolution with the first derivative of a Gaussian.
Definition: itkGradientRecursiveGaussianImageFilter.h:59
itkRescaleIntensityImageFilter.h
itkImageFileWriter.h
itk::CovariantVector
A templated class holding a n-Dimensional covariant vector.
Definition: itkCovariantVector.h:70
itk
The "itk" namespace contains all Insight Segmentation and Registration Toolkit (ITK) classes....
Definition: itkAnnulusOperator.h:24
itk::RescaleIntensityImageFilter
Applies a linear transformation to the intensity levels of the input Image.
Definition: itkRescaleIntensityImageFilter.h:154
itk::Image
Templated n-dimensional image class.
Definition: itkImage.h:86
itk::GTest::TypedefsAndConstructors::Dimension2::Dimension
constexpr unsigned int Dimension
Definition: itkGTestTypedefsAndConstructors.h:44