ITK  5.0.0
Insight Segmentation and Registration Toolkit
Examples/DataRepresentation/Image/ImageAdaptor3.cxx
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*
* Copyright Insight Software Consortium
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* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
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* http://www.apache.org/licenses/LICENSE-2.0.txt
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
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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() {}
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
}
// 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 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 = itk::ImageAdaptor< VectorImageType,
itk::VectorPixelAccessor >;
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 = itk::RescaleIntensityImageFilter< ImageAdaptorType,
OutputImageType>;
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;
}