/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/
#ifndef itkBSplineInterpolationWeightFunction_h
#define itkBSplineInterpolationWeightFunction_h

#include "itkFunctionBase.h"
#include "itkContinuousIndex.h"
#include "itkBSplineKernelFunction.h"
#include "itkArray.h"
#include "itkArray2D.h"

namespace itk
{
/** \class BSplineInterpolationWeightFunction
 * \brief Returns the weights over the support region used for B-spline
 * interpolation/reconstruction.
 *
 * Computes/evaluate the B-spline interpolation weights over the
 * support region of the B-spline.
 *
 * This class is templated over the coordinate representation type,
 * the space dimension and the spline order.
 *
 * \sa Point
 * \sa Index
 * \sa ContinuousIndex
 *
 * \ingroup Functions ImageInterpolators
 * \ingroup ITKCommon
 */
template<
  typename TCoordRep = float,
  unsigned int VSpaceDimension = 2,
  unsigned int VSplineOrder = 3
  >
class BSplineInterpolationWeightFunction:
  public FunctionBase< ContinuousIndex< TCoordRep, VSpaceDimension >,
                       Array< double > >
{
public:
  /** Standard class typedefs. */
  typedef BSplineInterpolationWeightFunction Self;
  typedef FunctionBase< ContinuousIndex< TCoordRep, VSpaceDimension >,
                        Array< double > >                  Superclass;

  typedef SmartPointer< Self >       Pointer;
  typedef SmartPointer< const Self > ConstPointer;

  /** New macro for creation of through the object factory. */
  itkNewMacro(Self);

  /** Run-time type information (and related methods). */
  itkTypeMacro(BSplineInterpolationWeightFunction, FunctionBase);

  /** Space dimension. */
  itkStaticConstMacro(SpaceDimension, unsigned int, VSpaceDimension);

  /** Spline order. */
  itkStaticConstMacro(SplineOrder, unsigned int, VSplineOrder);

  /** OutputType typedef support. */
  typedef Array< double > WeightsType;

  /** Index and size typedef support. */
  typedef Index< VSpaceDimension > IndexType;
  typedef Size< VSpaceDimension >  SizeType;

  /** ContinuousIndex typedef support. */
  typedef ContinuousIndex< TCoordRep, VSpaceDimension > ContinuousIndexType;

  /** Evaluate the weights at specified ContinuousIndex position.
   * Subclasses must provide this method. */
  virtual WeightsType Evaluate(const ContinuousIndexType & index) const ITK_OVERRIDE;

  /** Evaluate the weights at specified ContinuousIndex position.
   * The weights are returned in the user specified container.
   * This function assume that weights can hold
   * (SplineOrder + 1)^(SpaceDimension) elements. For efficiency,
   * no size checking is done.
   * On return, startIndex contains the start index of the
   * support region over which the weights are defined.
   */
  virtual void Evaluate(const ContinuousIndexType & index,
                        WeightsType & weights, IndexType & startIndex) const;

  /** Get support region size. */
  itkGetConstMacro(SupportSize, SizeType);

  /** Get number of weights. */
  itkGetConstMacro(NumberOfWeights, unsigned int);

protected:
  BSplineInterpolationWeightFunction();
  ~BSplineInterpolationWeightFunction() {}
  void PrintSelf(std::ostream & os, Indent indent) const ITK_OVERRIDE;

private:
  BSplineInterpolationWeightFunction(const Self &) ITK_DELETE_FUNCTION;
  void operator=(const Self &) ITK_DELETE_FUNCTION;

  /** Number of weights. */
  unsigned int m_NumberOfWeights;

  /** Size of support region. */
  SizeType m_SupportSize;

  /** Lookup table type. */
  typedef Array2D< unsigned int > TableType;

  /** Table mapping linear offset to indices. */
  TableType m_OffsetToIndexTable;

  /** Interpolation kernel type. */
  typedef BSplineKernelFunction< itkGetStaticConstMacro(SplineOrder) > KernelType;

  /** Interpolation kernel. */
  typename KernelType::Pointer m_Kernel;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkBSplineInterpolationWeightFunction.hxx"
#endif

#endif
