Examples/Filtering/OtsuMultipleThresholdImageFilter.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.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
 
//  Software Guide : BeginCommandLineArgs
//    INPUTS: {BrainProtonDensitySlice.png}
//    ARGUMENTS:   OtsuMultipleThresholdsOutput png 4
//  Software Guide : EndCommandLineArgs
 
// Software Guide : BeginLatex
//
// This example illustrates how to use the
// \doxygen{OtsuMultipleThresholdsCalculator}.
//
// Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkOtsuMultipleThresholdsCalculator.h"
// Software Guide : EndCodeSnippet
 
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkScalarImageToHistogramGenerator.h"
#include "itkBinaryThresholdImageFilter.h"
#include "itkNumericTraits.h"
 
#include <iomanip>
#include <cstdio>
 
int
main(int argc, char * argv[])
{
  if (argc < 5)
  {
    std::cerr << "Usage: " << argv[0];
    std::cerr << " inputImageFile outputImageFileBase ";
    std::cerr << "  outputImageFileExtension numberOfThresholdsToCalculate "
              << std::endl;
    return EXIT_FAILURE;
  }
 
  // Convenience type alias
  using InputPixelType = unsigned short;
  using OutputPixelType = unsigned char;
 
  using InputImageType = itk::Image<InputPixelType, 2>;
  using OutputImageType = itk::Image<OutputPixelType, 2>;
 
  // Software Guide : BeginLatex
  //
  // \code{OtsuMultipleThresholdsCalculator} calculates thresholds for a given
  // histogram so as to maximize the between-class variance. We use
  // \code{ScalarImageToHistogramGenerator} to generate histograms. The
  // histogram type defined by the generator is then used to instantiate the
  // type of the Otsu threshold calculator.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using ScalarImageToHistogramGeneratorType =
    itk::Statistics::ScalarImageToHistogramGenerator<InputImageType>;
 
  using HistogramType = ScalarImageToHistogramGeneratorType::HistogramType;
 
  using CalculatorType = itk::OtsuMultipleThresholdsCalculator<HistogramType>;
  // Software Guide : EndCodeSnippet
 
  using ReaderType = itk::ImageFileReader<InputImageType>;
  using WriterType = itk::ImageFileWriter<OutputImageType>;
 
  // Software Guide : BeginLatex
  //
  // Once thresholds are computed we will use
  // \code{BinaryThresholdImageFilter} to segment the input image.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using FilterType =
    itk::BinaryThresholdImageFilter<InputImageType, OutputImageType>;
  // Software Guide : EndCodeSnippet
 
  // Software Guide : BeginLatex
  //
  // Create a histogram generator and calculator using the standard
  // \code{New()} method.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  ScalarImageToHistogramGeneratorType::Pointer
    scalarImageToHistogramGenerator =
      ScalarImageToHistogramGeneratorType::New();
 
  auto calculator = CalculatorType::New();
  auto filter = FilterType::New();
  // Software Guide : EndCodeSnippet
 
  auto reader = ReaderType::New();
  auto writer = WriterType::New();
 
  // Software Guide : BeginLatex
  //
  // Set the following properties for the histogram generator and the
  // calculators, in this case grabbing the number of thresholds from
  // the command line.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  scalarImageToHistogramGenerator->SetNumberOfBins(128);
  calculator->SetNumberOfThresholds(std::stoi(argv[4]));
  // Software Guide : EndCodeSnippet
 
  calculator->SetReturnBinMidpoint(true); // regression test requires this
 
  constexpr OutputPixelType outsideValue = 0;
  constexpr OutputPixelType insideValue = 255;
 
  filter->SetOutsideValue(outsideValue);
  filter->SetInsideValue(insideValue);
 
  // Connect Pipeline
  reader->SetFileName(argv[1]);
 
  // Software Guide : BeginLatex
  //
  // The pipeline will look as follows:
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  scalarImageToHistogramGenerator->SetInput(reader->GetOutput());
  calculator->SetInputHistogram(scalarImageToHistogramGenerator->GetOutput());
  filter->SetInput(reader->GetOutput());
  writer->SetInput(filter->GetOutput());
  // Software Guide : EndCodeSnippet
 
 
  // Invoke pipeline
  try
  {
    reader->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown while reading image" << excp << std::endl;
  }
  scalarImageToHistogramGenerator->Compute();
 
  try
  {
    calculator->Compute();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << excp << std::endl;
  }
 
  // Software Guide : BeginLatex
  //
  // Here we obtain a \code{const} reference to the thresholds by calling
  // the \code{GetOutput()} method.
  // \index{itk::OtsuMultipleThresholdsCalculator!GetOutput()}
  //
  // Software Guide : EndLatex
 
  // Get Thresholds
 
  // Software Guide : BeginCodeSnippet
  const CalculatorType::OutputType & thresholdVector =
    calculator->GetOutput();
  // Software Guide : EndCodeSnippet
 
  // Software Guide : BeginLatex
  //
  // We now iterate through \code{thresholdVector}, printing each value to the
  // console and writing an image thresholded with adjacent values from the
  // container.  (In the edge cases, the minimum and maximum values of the
  // \code{InternalPixelType} are used).
  //
  // Software Guide : EndLatex
 
  std::string outputFileBase = argv[2];
 
  InputPixelType lowerThreshold = itk::NumericTraits<InputPixelType>::min();
  InputPixelType upperThreshold;
 
  // Software Guide : BeginCodeSnippet
  for (auto itNum = thresholdVector.begin(); itNum != thresholdVector.end();
       ++itNum)
  {
    std::cout
      << "OtsuThreshold[" << static_cast<int>(itNum - thresholdVector.begin())
      << "] = "
      << static_cast<
           itk::NumericTraits<CalculatorType::MeasurementType>::PrintType>(
           *itNum)
      << std::endl;
    // Software Guide : EndCodeSnippet
 
    upperThreshold = static_cast<InputPixelType>(*itNum);
 
    filter->SetLowerThreshold(lowerThreshold);
    filter->SetUpperThreshold(upperThreshold);
 
    lowerThreshold = upperThreshold;
 
    std::ostringstream outputFilename;
    outputFilename << outputFileBase << std::setfill('0') << std::setw(3)
                   << (itNum - thresholdVector.begin()) << "." << argv[3];
    writer->SetFileName(outputFilename.str());
 
    try
    {
      writer->Update();
    }
    catch (const itk::ExceptionObject & excp)
    {
      std::cerr << "Exception thrown " << excp << std::endl;
    }
  }
 
  // Software Guide : BeginLatex
  //
  // Also write out the image thresholded between the upper threshold and
  // the max intensity.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  upperThreshold = itk::NumericTraits<InputPixelType>::max();
  filter->SetLowerThreshold(lowerThreshold);
  filter->SetUpperThreshold(upperThreshold);
  // Software Guide : EndCodeSnippet
 
  std::ostringstream outputFilename2;
  outputFilename2 << outputFileBase << std::setfill('0') << std::setw(3)
                  << thresholdVector.size() << "." << argv[3];
  writer->SetFileName(outputFilename2.str());
 
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << excp << std::endl;
  }
 
  return EXIT_SUCCESS;
}