Examples/Filtering/SpatialObjectToImage2.cxx

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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 : BeginLatex
//
//  This example illustrates the use of the
//  \doxygen{GaussianSpatialObjects} for composing complex smoothed shapes by
//  aggregating them in a group. This process is equivalent to what is called
//  ''MetaBalls'' in Computer Graphics.
//
//  See http://en.wikipedia.org/wiki/Metaballs
//
//
//  \index{itk::SpatialObjectToImageFilter|textbf}
//
//  Software Guide : EndLatex

//  Software Guide : BeginLatex
//
//  We include the header file of the SpatialObjectToImageFilter since we will
//  use it to rasterize the group of spatial objects into an image.
//
//  \index{itk::SpatialObjectToImageFilter!header}
//
//  Software Guide : EndLatex


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


//  Software Guide : BeginLatex
//
//  Then we include the header of the GaussianSpatialObject that we will use as
//  elementary shape.
//
//  \index{itk::GaussianSpatialObject!header}
//
//  Software Guide : EndLatex


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


//  Software Guide : BeginLatex
//
//  Then we include the header of the \doxygen{GroupSpatialObject} that will
//  group together these instances of SpatialObjects.
//
//  \index{itk::GroupSpatialObject!header}
//
//  Software Guide : EndLatex

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


#include "itkImageFileWriter.h"


int main( int argc, char *argv[] )
{
  if( argc != 2 )
    {
    std::cerr << "Usage: " << argv[0] << " outputimagefile " << std::endl;
    return EXIT_FAILURE;
    }


  //  Software Guide : BeginLatex
  //
  //  We declare the pixel type and dimension of the image to be produced as
  //  output.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using PixelType = signed short;
  constexpr unsigned int Dimension = 3;

  using ImageType = itk::Image< PixelType, Dimension >;
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Using the same dimension, we instantiate the types of the elementary
  //  SpatialObjects that we plan to group, and we instantiate as well the type
  //  of the SpatialObject that will hold the group together.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using MetaBallType = itk::GaussianSpatialObject< Dimension >;
  using GroupType = itk::GroupSpatialObject< Dimension >;
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  We instantiate the SpatialObjectToImageFilter type by using as template
  //  arguments the input SpatialObject and the output image types.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using SpatialObjectToImageFilterType = itk::SpatialObjectToImageFilter<
    GroupType, ImageType >;

  SpatialObjectToImageFilterType::Pointer imageFilter =
    SpatialObjectToImageFilterType::New();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The SpatialObjectToImageFilter requires that the user defines the grid
  //  parameters of the output image. This includes the number of pixels along
  //  each dimension, the pixel spacing, image direction and
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  ImageType::SizeType size;
  size[ 0 ] =  50;
  size[ 1 ] =  50;
  size[ 2 ] = 200;

  imageFilter->SetSize( size );
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginCodeSnippet
  ImageType::SpacingType spacing;
  spacing[0] =  100.0 / size[0];
  spacing[1] =  100.0 / size[1];
  spacing[2] =  400.0 / size[2];

  imageFilter->SetSpacing( spacing );
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  We create the elementary shapes that are going to be composed into the
  //  group spatial objects.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  MetaBallType::Pointer metaBall1 = MetaBallType::New();
  MetaBallType::Pointer metaBall2 = MetaBallType::New();
  MetaBallType::Pointer metaBall3 = MetaBallType::New();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The Elementary shapes have internal parameters of their own. These
  //  parameters define the geometrical characteristics of the basic shapes.
  //  For example, a cylinder is defined by its radius and height.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  metaBall1->SetRadiusInObjectSpace(  size[0] * spacing[0] * 0.2 );
  metaBall2->SetRadiusInObjectSpace(  size[0] * spacing[0] * 0.2 );
  metaBall3->SetRadiusInObjectSpace(  size[0] * spacing[0] * 0.2 );
  // Software Guide : EndCodeSnippet

  metaBall1->SetMaximum( 1000.0 );
  metaBall2->SetMaximum( 1000.0 );
  metaBall3->SetMaximum( 1000.0 );

  //  Software Guide : BeginLatex
  //
  //  Each one of these components will be placed in a different position and
  //  orientation. We define transforms in order to specify those relative
  //  positions and orientations.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using TransformType = GroupType::TransformType;

  TransformType::Pointer transform1 = TransformType::New();
  TransformType::Pointer transform2 = TransformType::New();
  TransformType::Pointer transform3 = TransformType::New();

  transform1->SetIdentity();
  transform2->SetIdentity();
  transform3->SetIdentity();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Then we set the specific values of the transform parameters, and we
  //  assign the transforms to the elementary shapes.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  TransformType::OutputVectorType  translation;

  translation[ 0 ] =  size[0] * spacing[0] / 2.0;
  translation[ 1 ] =  size[1] * spacing[1] / 4.0;
  translation[ 2 ] =  size[2] * spacing[2] / 2.0;
  transform1->Translate( translation, false );

  translation[ 1 ] =  size[1] * spacing[1] / 2.0;
  translation[ 2 ] =  size[2] * spacing[2] * 0.22;
  transform2->Rotate( 1, 2, itk::Math::pi / 2.0 );
  transform2->Translate( translation, false );

  translation[ 2 ] = size[2] * spacing[2] * 0.78;
  transform3->Rotate( 1, 2, itk::Math::pi / 2.0 );
  transform3->Translate( translation, false );

  metaBall1->SetObjectToParentTransform( transform1 );
  metaBall2->SetObjectToParentTransform( transform2 );
  metaBall3->SetObjectToParentTransform( transform3 );
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The elementary shapes are aggregated in a parent group, that in turn is
  //  passed as input to the filter.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  GroupType::Pointer group = GroupType::New();
  group->AddChild( metaBall1 );
  group->AddChild( metaBall2 );
  group->AddChild( metaBall3 );

  metaBall1->Update();
  metaBall2->Update();
  metaBall3->Update();

  imageFilter->SetInput(  group  );
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  By default, the filter will rasterize the aggregation of elementary
  //  shapes and will assign a pixel value to locations that fall inside of any
  //  of the elementary shapes, and a different pixel value to locations that
  //  fall outside of all of the elementary shapes. In this case, we actually
  //  want the values of the Gaussians (MetaBalls) to be used in order produce
  //  the equivalent of a smooth fusion effect among the shapes.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  const PixelType airHounsfieldUnits  = -1000;

  imageFilter->SetUseObjectValue( true );
  imageFilter->SetOutsideValue( airHounsfieldUnits );
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  Finally we are ready to run the filter. We use the typical invocation of
  //  the \code{Update} method, and we instantiate an \code{ImageFileWriter} in
  //  order to save the generated image into a file.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using WriterType = itk::ImageFileWriter< ImageType >;
  WriterType::Pointer writer = WriterType::New();

  writer->SetFileName( argv[1] );
  writer->SetInput( imageFilter->GetOutput() );

  try
    {
    imageFilter->Update();
    writer->Update();
    }
  catch( itk::ExceptionObject & excp )
    {
    std::cerr << excp << std::endl;
    return EXIT_FAILURE;
    }
  // Software Guide : EndCodeSnippet


  return EXIT_SUCCESS;
}