WikiExamples/ImageProcessing/ResampleSegmentedImage.cxx

#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkIdentityTransform.h"
#include "itkLabelImageGaussianInterpolateImageFunction.h"
#include "itkNearestNeighborInterpolateImageFunction.h"
#include "itkResampleImageFilter.h"

#include "itkCustomColormapFunction.h"
#include "itkScalarToRGBColormapImageFilter.h"
#include "itkRGBPixel.h"
#include "itkMersenneTwisterRandomVariateGenerator.h"

#include "QuickView.h"

#include <iostream>
 
using InputPixelType = unsigned short;
using ImageType = itk::Image<InputPixelType, 2>;
using RGBPixelType = itk::RGBPixel<unsigned char>;
using RGBImageType = itk::Image<RGBPixelType, 2>;

using ColormapType = itk::Function::CustomColormapFunction<
  ImageType::PixelType, RGBImageType::PixelType>;

static void CreateRandomColormap(unsigned int size, ColormapType::Pointer colormap);

int main( int argc, char * argv[] )
{
  if( argc != 3 )
    { 
    std::cerr << "Usage: " << argv[0]
              << " inputImageFile pixelSize"
              << std::endl;
    
    return EXIT_FAILURE;
    }
  double spacing = atof(argv[2]);
 
  using ReaderType = itk::ImageFileReader<ImageType>;
 
  // Identity transform.
  // We don't want any transform on our image except rescaling which is not
  // specified by a transform but by the input/output spacing as we will see
  // later.
  // So no transform will be specified.
  using TransformType = itk::IdentityTransform<double, 2>;
 
  using GaussianInterpolatorType = itk::LabelImageGaussianInterpolateImageFunction<ImageType, double>;
  using NearestNeighborInterpolatorType = itk::NearestNeighborInterpolateImageFunction<ImageType, double>;
 
  using ResampleFilterType = itk::ResampleImageFilter<ImageType, ImageType>;

  // Prepare the reader and update it right away to know the sizes beforehand.
  ReaderType::Pointer reader =
    ReaderType::New();
  reader->SetFileName( argv[1] );
  reader->Update();
 
  // Instantiate the transform and specify it should be the identity transform.
  TransformType::Pointer transform =
    TransformType::New();
  transform->SetIdentity();
 
  // Instantiate the interpolators
  GaussianInterpolatorType::Pointer gaussianInterpolator =
    GaussianInterpolatorType::New();
  gaussianInterpolator->SetSigma(1.0);
  gaussianInterpolator->SetAlpha(3.0);

  NearestNeighborInterpolatorType::Pointer nearestNeighborInterpolator =
    NearestNeighborInterpolatorType::New();
  
  // Instantiate the resamplers. Wire in the transforms and the interpolators.
  ResampleFilterType::Pointer resizeFilter1 =
    ResampleFilterType::New();
  resizeFilter1->SetTransform(transform);
  resizeFilter1->SetInterpolator(gaussianInterpolator);

  ResampleFilterType::Pointer resizeFilter2 =
    ResampleFilterType::New();
  resizeFilter2->SetTransform(transform);
  resizeFilter2->SetInterpolator(nearestNeighborInterpolator);
 
  //     Compute and set the output size
  //     
  //     The computation must be so that the following holds:
  //     
  //     new width         old x spacing
  //     ----------   =   ---------------
  //     old width         new x spacing
  //    
  //    
  //     new height         old y spacing
  //    ------------  =   ---------------
  //     old height         new y spacing
  //
  //     So either we specify new height and width and compute new spacings
  //     or we specify new spacing and compute new height and width
  //     and computations that follows need to be modified a little (as it is
  //     done at step 2 there:
  //       http://itk.org/Wiki/ITK/Examples/DICOM/ResampleDICOM)
  //

  // Fetch original image spacing.
  const ImageType::SpacingType& inputSpacing = 
    reader->GetOutput()->GetSpacing();
 
  double outputSpacing[2];
  outputSpacing[0] = spacing;
  outputSpacing[1] = spacing;
 
  // Fetch original image size
  const ImageType::RegionType& inputRegion = 
    reader->GetOutput()->GetLargestPossibleRegion();
  const ImageType::SizeType& inputSize = inputRegion.GetSize();
  unsigned int oldWidth = inputSize[0];
  unsigned int oldHeight = inputSize[1];

  unsigned int newWidth = (double) oldWidth * inputSpacing[0] / spacing;
  unsigned int newHeight = (double) oldHeight * inputSpacing[1] / spacing;

  // Set the output spacing as specified on the command line
  resizeFilter1->SetOutputSpacing(outputSpacing);
  resizeFilter2->SetOutputSpacing(outputSpacing);

  // Set the computed size
  itk::Size<2> outputSize = { {newWidth, newHeight} };
  resizeFilter1->SetSize(outputSize);
  resizeFilter2->SetSize(outputSize);
 
  // Specify the input for the resamplers
  resizeFilter1->SetInput(reader->GetOutput());
  resizeFilter2->SetInput(reader->GetOutput());
 
  // Display the images
  using ColormapFilterType = itk::ScalarToRGBColormapImageFilter<ImageType, RGBImageType>;
  ColormapFilterType::Pointer colormapFilter1 =
    ColormapFilterType::New();

  ColormapType::Pointer colormap
    = ColormapType::New();
  CreateRandomColormap(4096, colormap);

  colormapFilter1->SetInput (reader->GetOutput());
  colormapFilter1->SetColormap(colormap);

  ColormapFilterType::Pointer colormapFilter2 =
   ColormapFilterType::New();
  colormapFilter2->SetInput (resizeFilter1->GetOutput());
  colormapFilter2->SetColormap(colormap);

  ColormapFilterType::Pointer colormapFilter3 =
   ColormapFilterType::New();
  colormapFilter3->SetInput (resizeFilter2->GetOutput());
  colormapFilter3->SetColormap(colormap);

  QuickView viewer;
  std::stringstream desc;
  desc << itksys::SystemTools::GetFilenameName(argv[1]) << ": " << oldWidth << ", " << oldHeight;
  viewer.AddRGBImage(
    colormapFilter1->GetOutput(),
    true,
    desc.str());  

  std::stringstream desc2;
  desc2 << "Gaussian Interpolation: " << newWidth << ", " << newHeight;
  viewer.AddRGBImage(
    colormapFilter2->GetOutput(),
    true,
    desc2.str());

  std::stringstream desc3;
  desc3 << "Nearest Neighbor Interpolation: " << newWidth << ", " << newHeight;
  viewer.AddRGBImage(
    colormapFilter3->GetOutput(),
    true,
    desc3.str());

  viewer.Visualize();

  return EXIT_SUCCESS;
}

void CreateRandomColormap(unsigned int size, ColormapType::Pointer colormap)
{
#define LOW .3
  ColormapType::ChannelType redChannel;
  ColormapType::ChannelType greenChannel;
  ColormapType::ChannelType blueChannel;
  itk::Statistics::MersenneTwisterRandomVariateGenerator::Pointer random =
    itk::Statistics::MersenneTwisterRandomVariateGenerator::New();

  random->SetSeed ( 8775070 );
  redChannel.push_back(LOW);
  greenChannel.push_back(LOW);
  blueChannel.push_back(LOW);
  for (unsigned int i = 1; i < size; ++i)
    {
    redChannel.push_back(static_cast<ColormapType::RealType>
                         (random->GetUniformVariate(LOW, 1.0)));
    greenChannel.push_back(static_cast<ColormapType::RealType>
                           (random->GetUniformVariate(LOW, 1.0)));
    blueChannel.push_back(static_cast<ColormapType::RealType>
                          (random->GetUniformVariate(LOW, 1.0)));
    }
  colormap->SetRedChannel(redChannel);
  colormap->SetGreenChannel(greenChannel);
  colormap->SetBlueChannel(blueChannel);
}