text: /*=========================================================================
   *
   *  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.
   *
   *=========================================================================*/
  /*=========================================================================
   *
   *  Portions of this file are subject to the VTK Toolkit Version 3 copyright.
   *
   *  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
   *
   *  For complete copyright, license and disclaimer of warranty information
   *  please refer to the NOTICE file at the top of the ITK source tree.
   *
   *=========================================================================*/
  #ifndef itkBSplineDownsampleImageFilter_h
  #define itkBSplineDownsampleImageFilter_h
  
  // include .h for each ResamplerType
  #include "itkBSplineL2ResampleImageFilterBase.h"
  #include "itkBSplineCenteredL2ResampleImageFilterBase.h"
  
  namespace itk
  {
  /** \class BSplineDownsampleImageFilter
   * \brief Down-samples an image by a factor of 2 using B-Spline filter interpolation.
   *
   * This class is the public interface for spline down-sampling as defined by the
   *   ResamplerType.
   * Requires the use of a resampler type.  If in doubt, the basic itkBSplineResampleImageFilterBase
   *   should work fine for most applications.
   *
   *  This class may also be used to create a smoother by combining it with the upSampler
   *  as in the following example:
   *      using ResamplerType = itk::BSplineResampleImageFilterBase<ImageType2D, ImageType2D>;
   *      using DownsamplerType2D = itk::BSplineDownsampleImageFilter<ImageType2D,ImageType2D,ResamplerType>;
   *      using UpsamplerType2D = itk::BSplineUpsampleImageFilter<ImageType2D,ImageType2D,ResamplerType>;
   *
   *      DownsamplerType2D::Pointer downSampler = DownsamplerType2D::New();
   *      UpsamplerType2D::Pointer   upSampler =   UpsamplerType2D::New();
   *      int splineOrder = 3;
   *      downSampler->SetSplineOrder(splineOrder);
   *      upSampler->SetSplineOrder(splineOrder);
   *
   *      downSampler->SetInput(image);
   *      downSampler->Update();
   *
   *      upSampler->SetInput( downSampler->GetOutput() );   // output of downSampler is input to upSampler
   *      upSampler->Update();
   *
   *      ImageTypePtr2D outImage2 = upSampler->GetOutput();  // outImage2 is the smoothed imaged
   *
   * Limitations:  This class requires specification of a resampler type which may
   *                      be one of:
   *                        itkBSplineResampleImageFilterBase,
   *                        itkBSplineL2ResampleImageFilterBase
   *                        itkBSplineSplineCenteredResampleImageFilterBase,
   *                        itkBSplineCenteredL2ResampleImageFilterBase
   *               The limitations of these resampler types will apply to this filter.
   *               Downsamples only by a factor of 2.
   *
   * \sa itkBSplineDownsampleImageFilter
   * \sa itkBSplineL2ResampleImageFilter
   * \sa itkBSplineResampleImageFilterBase
   * \sa itkBSplineCenteredResampleImageFilterBase
   * \sa itkBSplineCenteredL2ResampleImageFilterBase
   *
   * \ingroup GeometricTransformationFilters
   * \ingroup SingleThreaded
   * \ingroup CannotBeStreamed
   * \ingroup ITKImageGrid
   */
  
  //= typename BSplineResampleImageFilterBase<TInputImage, TOutputImage>
  template< typename TInputImage, typename TOutputImage,
            typename ResamplerType = BSplineResampleImageFilterBase< TInputImage, TOutputImage > >
  class ITK_TEMPLATE_EXPORT BSplineDownsampleImageFilter:
    public ResamplerType
  {
  public:
    ITK_DISALLOW_COPY_AND_ASSIGN(BSplineDownsampleImageFilter);
  
    /** Standard class type aliases. */
    using Self = BSplineDownsampleImageFilter;
    using Superclass = ResamplerType;
    using Pointer = SmartPointer< Self >;
    using ConstPointer = SmartPointer< const Self >;
  
    /** Run-time type information (and related methods). */
    itkTypeMacro(BSplineDownsampleImageFilter, ResamplerType);
  
    /** New macro for creation of through a Smart Pointer */
    itkNewMacro(Self);
  
    /** InputImageType type alias support */
    using InputImageType = typename Superclass::InputImageType;
  
    /** InputImagePointer type alias support */
    using InputImagePointer = typename Superclass::InputImagePointer;
  
    /** OutputImagePointer type alias support */
    using OutputImagePointer = typename Superclass::OutputImagePointer;
  
    /** OutputImageIterator type alias support */
    using OutputImageIterator = typename Superclass::OutputImageIterator;
  
    /** Creates an image half the size of the input image with spacing twice the
      * input image. */
    void GenerateOutputInformation() override;
  
    /** This filter requires all of the input image */
    void GenerateInputRequestedRegion() override;
  
  #ifdef ITK_USE_CONCEPT_CHECKING
    // Begin concept checking
    itkConceptMacro( DoubleConvertibleToOutputCheck,
                     ( Concept::Convertible< double, typename TOutputImage::PixelType > ) );
    // End concept checking
  #endif
  
  protected:
  
    void GenerateData() override;
  
    void EnlargeOutputRequestedRegion(DataObject *output) override;
  
    BSplineDownsampleImageFilter();
    ~BSplineDownsampleImageFilter() override {}
  };
  } // namespace itk
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #include "itkBSplineDownsampleImageFilter.hxx"
  #endif
  
  #endif
  