Examples/Filtering/ThresholdImageFilter.cxx

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 *  Copyright NumFOCUS
 *
 *  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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 *         https://www.apache.org/licenses/LICENSE-2.0.txt
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//  Software Guide : BeginCommandLineArgs
//    INPUTS: {BrainProtonDensitySlice.png}
//    OUTPUTS: {ThresholdImageFilterOutputBelow.png}
//    OUTPUTS: {ThresholdImageFilterOutputAbove.png}
//    OUTPUTS: {ThresholdImageFilterOutputOutside.png}
//  Software Guide : EndCommandLineArgs
 
// Software Guide : BeginLatex
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionBelow}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputBelow}
// \itkcaption[ThresholdImageFilter using the threshold-below
// mode.]{ThresholdImageFilter using the threshold-below mode.}
// \label{fig:ThresholdTransferFunctionBelow}
// \end{figure}
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionAbove}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputAbove}
// \itkcaption[ThresholdImageFilter using the threshold-above
// mode]{ThresholdImageFilter using the threshold-above mode.}
// \label{fig:ThresholdTransferFunctionAbove}
// \end{figure}
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionOutside}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputOutside}
// \itkcaption[ThresholdImageFilter using the threshold-outside
// mode]{ThresholdImageFilter using the threshold-outside mode.}
// \label{fig:ThresholdTransferFunctionOutside}
// \end{figure}
//
// This example illustrates the use of the \doxygen{ThresholdImageFilter}.
// This filter can be used to transform the intensity levels of an image in
// three different ways.
//
// \begin{itemize}
//
// \item First, the user can define a single threshold.  Any pixels with
// values below this threshold will be replaced by a user defined value,
// called here the \code{OutsideValue}.  Pixels with values above the
// threshold remain unchanged. This type of thresholding is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionBelow}.
//
// \item Second, the user can define a particular threshold such that all the
// pixels with values above the threshold will be replaced by the
// \code{OutsideValue}.  Pixels with values below the threshold remain
// unchanged. This is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionAbove}.
//
// \item Third, the user can provide two thresholds. All the pixels with
// intensity values inside the range defined by the two thresholds will remain
// unchanged. Pixels with values outside this range will be assigned to the
// \code{OutsideValue}. This is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionOutside}.
//
// \end{itemize}
//
// The following methods choose among the three operating modes of the filter.
//
// \begin{itemize}
// \item \texttt{ThresholdBelow()}
// \item \texttt{ThresholdAbove()}
// \item \texttt{ThresholdOutside()}
// \end{itemize}
//
// \index{itk::ThresholdImageFilter!Instantiation}
// \index{itk::ThresholdImageFilter!Header}
// \index{itk::ThresholdImageFilter!ThresholdAbove()}
// \index{itk::ThresholdImageFilter!ThresholdBelow()}
// \index{itk::ThresholdImageFilter!ThresholdOutside()}
//
// The first step required to use this filter is to include its header file.
//
// Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkThresholdImageFilter.h"
// Software Guide : EndCodeSnippet
 
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
 
int
main(int argc, char * argv[])
{
 
  if (argc < 5)
  {
    std::cerr << "Usage: " << argv[0] << " inputImageFile ";
    std::cerr << " outputImageFile1 outputImageFile2 outputImageFile3"
              << std::endl;
    return EXIT_FAILURE;
  }
 
  //  Software Guide : BeginLatex
  //
  //  Then we must decide what pixel type to use for the image. This filter is
  //  templated over a single image type because the algorithm only modifies
  //  pixel values outside the specified range, passing the rest through
  //  unchanged.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using PixelType = unsigned char;
  // Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //  The image is defined using the pixel type and the dimension.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using ImageType = itk::Image<PixelType, 2>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The filter can be instantiated using the image type defined above.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using FilterType = itk::ThresholdImageFilter<ImageType>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  An \doxygen{ImageFileReader} class is also instantiated in order to read
  //  image data from a file.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using ReaderType = itk::ImageFileReader<ImageType>;
  // Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  // An \doxygen{ImageFileWriter} is instantiated in order to write the
  // output image to a file.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using WriterType = itk::ImageFileWriter<ImageType>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  Both the filter and the reader are created by invoking their
  //  \code{New()} methods and assigning the result to SmartPointers.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  auto reader = ReaderType::New();
  auto filter = FilterType::New();
  // Software Guide : EndCodeSnippet
 
  auto writer = WriterType::New();
  writer->SetInput(filter->GetOutput());
  reader->SetFileName(argv[1]);
 
 
  //  Software Guide : BeginLatex
  //
  //  The image obtained with the reader is passed as input to the
  //  \doxygen{ThresholdImageFilter}.
  //
  //  \index{itk::ThresholdImageFilter!SetInput()}
  //  \index{itk::FileImageReader!GetOutput()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetInput(reader->GetOutput());
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The method \code{SetOutsideValue()} defines the intensity value to be
  //  assigned to those pixels whose intensities are outside the range defined
  //  by the lower and upper thresholds.
  //
  //  \index{itk::ThresholdImageFilter!SetOutsideValue()}
  //  \index{SetOutsideValue()!itk::ThresholdImageFilter}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetOutsideValue(0);
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The method \code{ThresholdBelow()} defines the intensity value below
  //  which pixels of the input image will be changed to the
  //  \code{OutsideValue}.
  //
  //  \index{itk::ThresholdImageFilter!ThresholdBelow()}
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->ThresholdBelow(180);
  // Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //  The filter is executed by invoking the \code{Update()} method. If the
  //  filter is part of a larger image processing pipeline, calling
  //  \code{Update()} on a downstream filter will also trigger update of this
  //  filter.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->Update();
  // Software Guide : EndCodeSnippet
 
 
  writer->SetFileName(argv[2]);
  writer->Update();
 
 
  //  Software Guide : BeginLatex
  //
  //  The output of this example is shown in
  //  Figure~\ref{fig:ThresholdTransferFunctionBelow}.  The second operating
  //  mode of the filter is now enabled by calling the method
  //  \code{ThresholdAbove()}.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->ThresholdAbove(180);
  filter->Update();
  // Software Guide : EndCodeSnippet
 
 
  writer->SetFileName(argv[3]);
  writer->Update();
 
  //  Software Guide : BeginLatex
  //
  //  Updating the filter with this new setting produces the output shown in
  //  Figure~\ref{fig:ThresholdTransferFunctionAbove}.  The third operating
  //  mode of the filter is enabled by calling \code{ThresholdOutside()}.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->ThresholdOutside(170, 190);
  filter->Update();
  // Software Guide : EndCodeSnippet
 
 
  writer->SetFileName(argv[4]);
  writer->Update();
 
 
  //  Software Guide : BeginLatex
  //
  //  The output of this third, ``band-pass'' thresholding mode is shown in
  //  Figure~\ref{fig:ThresholdTransferFunctionOutside}.
  //
  //  The examples in this
  //  section also illustrate the limitations of the thresholding filter for
  //  performing segmentation by itself. These limitations are particularly
  //  noticeable in noisy images and in images lacking spatial uniformity, as
  //  is the case with MRI due to field bias.
  //
  //  \relatedClasses
  //  \begin{itemize}
  //  \item \doxygen{BinaryThresholdImageFilter}
  //  \end{itemize}
  //
  //  Software Guide : EndLatex
 
 
  return EXIT_SUCCESS;
}