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 itkImageRandomConstIteratorWithIndex_hxx
  #define itkImageRandomConstIteratorWithIndex_hxx
  
  #include "itkImageRandomConstIteratorWithIndex.h"
  
  namespace itk
  {
  /** Default constructor. Needed since we provide a cast constructor. */
  template< typename TImage >
  ImageRandomConstIteratorWithIndex< TImage >
  ::ImageRandomConstIteratorWithIndex():ImageConstIteratorWithIndex< TImage >()
  {
    m_NumberOfPixelsInRegion    = 0L;
    m_NumberOfSamplesRequested  = 0L;
    m_NumberOfSamplesDone       = 0L;
    m_Generator = Statistics::MersenneTwisterRandomVariateGenerator::GetInstance();
  }
  
  /** Constructor establishes an iterator to walk a particular image and a
   * particular region of that image. */
  template< typename TImage >
  ImageRandomConstIteratorWithIndex< TImage >
  ::ImageRandomConstIteratorWithIndex(const ImageType *ptr, const RegionType & region):
    ImageConstIteratorWithIndex< TImage >(ptr, region)
  {
    m_NumberOfPixelsInRegion   = region.GetNumberOfPixels();
    m_NumberOfSamplesRequested = 0L;
    m_NumberOfSamplesDone      = 0L;
    m_Generator = Statistics::MersenneTwisterRandomVariateGenerator::GetInstance();
  }
  
  /**  Set the number of samples to extract from the region */
  template< typename TImage >
  void
  ImageRandomConstIteratorWithIndex< TImage >
  ::SetNumberOfSamples(SizeValueType number)
  {
    m_NumberOfSamplesRequested = number;
  }
  
  /**  Set the number of samples to extract from the region */
  template< typename TImage >
  typename ImageRandomConstIteratorWithIndex< TImage >::SizeValueType
  ImageRandomConstIteratorWithIndex< TImage >
  ::GetNumberOfSamples(void) const
  {
    return m_NumberOfSamplesRequested;
  }
  
  /** Reinitialize the seed of the random number generator */
  template< typename TImage >
  void
  ImageRandomConstIteratorWithIndex< TImage >
  ::ReinitializeSeed()
  {
    m_Generator->SetSeed();
  }
  
  template< typename TImage >
  void
  ImageRandomConstIteratorWithIndex< TImage >
  ::ReinitializeSeed(int seed)
  {
    m_Generator->SetSeed (seed);
    // vnl_sample_reseed(seed);
  }
  
  /** Execute an acrobatic random jump */
  template< typename TImage >
  void
  ImageRandomConstIteratorWithIndex< TImage >
  ::RandomJump()
  {
    typedef IndexValueType PositionValueType;
  
    const PositionValueType randomPosition =
      static_cast< PositionValueType >( m_Generator->GetVariateWithOpenRange (static_cast< double >( m_NumberOfPixelsInRegion )
                                                                          - 0.5) );
    /*
        vnl_sample_uniform(0.0f,
        static_cast<double>(m_NumberOfPixelsInRegion)-0.5) );
    */
  
    PositionValueType position = randomPosition;
    PositionValueType residual;
  
    for ( unsigned int dim = 0; dim < TImage::ImageDimension; dim++ )
      {
      const SizeValueType sizeInThisDimension = this->m_Region.GetSize()[dim];
      residual = position % sizeInThisDimension;
      this->m_PositionIndex[dim] =  residual + this->m_BeginIndex[dim];
      position -= residual;
      position /= sizeInThisDimension;
      }
  
    this->m_Position = this->m_Image->GetBufferPointer() + this->m_Image->ComputeOffset(this->m_PositionIndex);
  }
  } // end namespace itk
  
  #endif
  