/*=========================================================================
 *
 *  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 itkSpeckleNoiseImageFilter_h
#define itkSpeckleNoiseImageFilter_h

#include "itkNoiseBaseImageFilter.h"

namespace itk
{

/** \class SpeckleNoiseImageFilter
 *
 * \brief Alter an image with speckle (multiplicative) noise.
 *
 * The speckle noise follows a gamma distribution of mean 1 and standard deviation
 * provided by the user. The noise is proportional to the pixel intensity.
 *
 * It can be modeled as:
 *
 * \par
 * \f$ I = I_0 \ast G \f$
 *
 * \par
 * where \f$ G \f$ is a is a gamma distributed random variable of mean 1 and
 * variance proportional to the noise level:
 *
 * \par
 * \f$ G \sim \Gamma(\frac{1}{\sigma^2}, \sigma^2) \f$
 *
 * \author Gaetan Lehmann
 *
 * This code was contributed in the Insight Journal paper "Noise
 * Simulation". https://hdl.handle.net/10380/3158
 *
 * \ingroup ITKImageNoise
 */
template <class TInputImage, class TOutputImage=TInputImage>
class ITK_TEMPLATE_EXPORT SpeckleNoiseImageFilter :
  public NoiseBaseImageFilter<TInputImage,TOutputImage >
{
public:
  /** Standard class typedefs. */
  typedef SpeckleNoiseImageFilter                          Self;
  typedef NoiseBaseImageFilter< TInputImage,TOutputImage > Superclass;
  typedef SmartPointer<Self>                               Pointer;
  typedef SmartPointer<const Self>                         ConstPointer;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

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

  /** Superclass typedefs. */
  typedef typename Superclass::OutputImageType       OutputImageType;
  typedef typename Superclass::OutputImagePointer    OutputImagePointer;
  typedef typename Superclass::OutputImageRegionType OutputImageRegionType;
  typedef typename Superclass::OutputImagePixelType  OutputImagePixelType;

  /** Some convenient typedefs. */
  typedef TInputImage                           InputImageType;
  typedef typename InputImageType::Pointer      InputImagePointer;
  typedef typename InputImageType::ConstPointer InputImageConstPointer;
  typedef typename InputImageType::RegionType   InputImageRegionType;
  typedef typename InputImageType::PixelType    InputImagePixelType;

  /** Set/Get the standard deviation of the gamma distribution.
   * Defaults to 1.0. */
  itkGetConstMacro(StandardDeviation, double);
  itkSetMacro(StandardDeviation, double);

#ifdef ITK_USE_CONCEPT_CHECKING
  /** Begin concept checking */
  itkConceptMacro(InputConvertibleToOutputCheck,
                  (Concept::Convertible<typename TInputImage::PixelType,
                                        typename TOutputImage::PixelType>) );
  /** End concept checking */
#endif

protected:
  SpeckleNoiseImageFilter();
  virtual ~SpeckleNoiseImageFilter()  ITK_OVERRIDE {}

  void PrintSelf(std::ostream & os, Indent indent) const ITK_OVERRIDE;

  void ThreadedGenerateData(const OutputImageRegionType& outputRegionForThread, ThreadIdType threadId ) ITK_OVERRIDE;

private:
  ITK_DISALLOW_COPY_AND_ASSIGN(SpeckleNoiseImageFilter);

  double m_StandardDeviation;

};
} // end namespace itk

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

#endif
