Compute Derivative#

Synopsis#

This filter computes a n-th Derivative of a scalar-valued image in a specified direction.

Results#

Code#

C++#

//  Software Guide : BeginCommandLineArgs
//    INPUTS:  {BrainProtonDensitySlice.png}
//    ARGUMENTS: {DerivativeImageFilterFloatOutput.mhd}
//    OUTPUTS: {DerivativeImageFilterOutput.png}
//    ARGUMENTS:    1 0
//  Software Guide : EndCommandLineArgs

//  Software Guide : BeginLatex
//
//  The \doxygen{DerivativeImageFilter} is used for computing the partial
//  derivative of an image, the derivative of an image along a particular
//  axial direction.
//
//  \index{itk::DerivativeImageFilter}
//
//  Software Guide : EndLatex


#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkRescaleIntensityImageFilter.h"

//  Software Guide : BeginLatex
//
//  The header file corresponding to this filter should be included first.
//
//  \index{itk::DerivativeImageFilter!header}
//
//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet
#include "itkDerivativeImageFilter.h"
// Software Guide : EndCodeSnippet


int
main(int argc, char * argv[])
{
  if (argc < 6)
  {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << "  inputImageFile   outputImageFile  normalizedOutputImageFile ";
    std::cerr << " derivativeOrder direction" << std::endl;
    return EXIT_FAILURE;
  }


  //  Software Guide : BeginLatex
  //
  //  Next, the pixel types for the input and output images must be defined
  //  and, with them, the image types can be instantiated. Note that it is
  //  important to select a signed type for the image, since the values of the
  //  derivatives will be positive as well as negative.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using InputPixelType = float;
  using OutputPixelType = float;

  constexpr unsigned int Dimension = 2;

  using InputImageType = itk::Image<InputPixelType, Dimension>;
  using OutputImageType = itk::Image<OutputPixelType, Dimension>;
  // Software Guide : EndCodeSnippet


  using ReaderType = itk::ImageFileReader<InputImageType>;
  using WriterType = itk::ImageFileWriter<OutputImageType>;

  auto reader = ReaderType::New();
  auto writer = WriterType::New();

  reader->SetFileName(argv[1]);
  writer->SetFileName(argv[2]);

  //  Software Guide : BeginLatex
  //
  //  Using the image types, it is now possible to define the filter type
  //  and create the filter object.
  //
  //  \index{itk::DerivativeImageFilter!instantiation}
  //  \index{itk::DerivativeImageFilter!New()}
  //  \index{itk::DerivativeImageFilter!Pointer}
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using FilterType = itk::DerivativeImageFilter<InputImageType, OutputImageType>;

  auto filter = FilterType::New();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The order of the derivative is selected with the \code{SetOrder()}
  //  method.  The direction along which the derivative will be computed is
  //  selected with the \code{SetDirection()} method.
  //
  //  \index{itk::DerivativeImageFilter!SetOrder()}
  //  \index{itk::DerivativeImageFilter!SetDirection()}
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  filter->SetOrder(std::stoi(argv[4]));
  filter->SetDirection(std::stoi(argv[5]));
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The input to the filter can be taken from any other filter, for example
  //  a reader. The output can be passed down the pipeline to other filters,
  //  for example, a writer. An \code{Update()} call on any downstream filter
  //  will trigger the execution of the derivative filter.
  //
  //  \index{itk::DerivativeImageFilter!SetInput()}
  //  \index{itk::DerivativeImageFilter!GetOutput()}
  //
  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet
  filter->SetInput(reader->GetOutput());
  writer->SetInput(filter->GetOutput());
  writer->Update();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  // \begin{figure}
  // \center
  // \includegraphics[width=0.44\textwidth]{BrainProtonDensitySlice}
  // \includegraphics[width=0.44\textwidth]{DerivativeImageFilterOutput}
  // \itkcaption[Effect of the Derivative filter.]{Effect of the Derivative
  // filter on a slice from a MRI proton density brain image.}
  // \label{fig:DerivativeImageFilterOutput}
  // \end{figure}
  //
  //  Figure \ref{fig:DerivativeImageFilterOutput} illustrates the effect of
  //  the DerivativeImageFilter on a slice of MRI brain image. The derivative
  //  is taken along the $x$ direction.  The sensitivity to noise in the image
  //  is evident from this result.
  //
  //  Software Guide : EndLatex


  using WriteImageType = itk::Image<unsigned char, Dimension>;

  using NormalizeFilterType = itk::RescaleIntensityImageFilter<OutputImageType, WriteImageType>;

  using NormalizedWriterType = itk::ImageFileWriter<WriteImageType>;

  auto normalizer = NormalizeFilterType::New();
  auto normalizedWriter = NormalizedWriterType::New();

  normalizer->SetInput(filter->GetOutput());
  normalizedWriter->SetInput(normalizer->GetOutput());

  normalizer->SetOutputMinimum(0);
  normalizer->SetOutputMaximum(255);

  normalizedWriter->SetFileName(argv[3]);
  normalizedWriter->Update();

  return EXIT_SUCCESS;
}

Classes demonstrated#

template<typename TInputImage, typename TOutputImage> class DerivativeImageFilter : public itk::ImageToImageFilter<TInputImage, TOutputImage>

Computes the directional derivative of an image. The directional derivative at each pixel location is computed by convolution with a derivative operator of user-specified order.

SetOrder specifies the order of the derivative.

SetDirection specifies the direction of the derivative with respect to the coordinate axes of the image.

See

Image

See

Neighborhood

See

NeighborhoodOperator

See

NeighborhoodIterator

ITK Sphinx Examples: