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.
   *
   *=========================================================================*/
  #ifndef __itkBackwardDifferenceOperator_h
  #define __itkBackwardDifferenceOperator_h
  
  #include "itkNeighborhoodOperator.h"
  
  namespace itk
  {
  /**
   * \class BackwardDifferenceOperator
   * \brief Operator whose inner product with a neighborhood returns
   * a "half" derivative at the center of the neighborhood.
   *
   * BackwardDifferenceOperator uses backward differences
   * i.e. F(x) - F(x-1) to calculate a "half" derivative useful, among
   * other things, in solving differential equations. It is a directional
   * NeighborhoodOperator that should be applied to a Neighborhood using the
   * inner product.
   *
   * \ingroup Operators
   *
   * \ingroup ITKCommon
   *
   * \wiki
   * \wikiexample{Operators/BackwardDifferenceOperator,Create a backward difference kernel}
   * \endwiki
   */
  template< class TPixel, unsigned int TDimension = 2,
            class TAllocator = NeighborhoodAllocator< TPixel > >
  class BackwardDifferenceOperator:
    public NeighborhoodOperator< TPixel, TDimension, TAllocator >
  {
  public:
    /** Standard class typedefs. */
    typedef BackwardDifferenceOperator                             Self;
    typedef NeighborhoodOperator< TPixel, TDimension, TAllocator > Superclass;
  
    /** From Superclass */
    typedef typename Superclass::PixelType PixelType;
  
    /** Constructor. */
    BackwardDifferenceOperator() {}
  
  protected:
    /** Necessary to work around a compiler bug in VC++. */
    typedef typename Superclass::CoefficientVector CoefficientVector;
  
    /** Calculates operator coefficients. */
    CoefficientVector GenerateCoefficients();
  
    /** Arranges coefficients spatially in the memory buffer. */
    void Fill(const CoefficientVector & coeff)
    { this->FillCenteredDirectional(coeff); }
  
  private:
    BackwardDifferenceOperator(const Self & other); //purposely not implemented
    Self & operator=(const Self & other);           //purposely not implemented
  };
  } // namespace itk
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #include "itkBackwardDifferenceOperator.hxx"
  #endif
  
  #endif
  