/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://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 itkApproximateSignedDistanceMapImageFilter_hxx
#define itkApproximateSignedDistanceMapImageFilter_hxx


#include "itkNumericTraits.h"
#include "itkImageScanlineIterator.h"
#include "itkProgressAccumulator.h"

namespace itk
{

template <typename TInputImage, typename TOutputImage>
ApproximateSignedDistanceMapImageFilter<TInputImage, TOutputImage>::ApproximateSignedDistanceMapImageFilter()
  : m_IsoContourFilter(IsoContourType::New())
  , m_ChamferFilter(ChamferType::New())
  , m_InsideValue(NumericTraits<InputPixelType>::min())
  , m_OutsideValue(NumericTraits<InputPixelType>::max())
{}

template <typename TInputImage, typename TOutputImage>
void
ApproximateSignedDistanceMapImageFilter<TInputImage, TOutputImage>::GenerateData()
{
  ThreadIdType numberOfWorkUnits = this->GetNumberOfWorkUnits();

  OutputImagePointer output = this->GetOutput();

  using OutputRegionType = typename OutputImageType::RegionType;
  OutputRegionType oRegion = output->GetRequestedRegion();

  // Calculate the largest possible distance in the output image.
  // this maximum is the distance from one corner of the image to the other.
  OutputSizeType      outputSize = oRegion.GetSize();
  OutputSizeValueType maximumDistance = 0;

  for (unsigned int i = 0; i < InputImageDimension; ++i)
  {
    maximumDistance += outputSize[i] * outputSize[i];
  }

  // Cast to double and back because there's no sqrt defined for unsigned long,
  // which is the general SizeValueType.
  maximumDistance = static_cast<OutputSizeValueType>(std::sqrt(static_cast<double>(maximumDistance)));

  // Allocate the output
  this->AllocateOutputs();

  // Create a process accumulator for tracking the progress of this minipipeline
  auto progress = ProgressAccumulator::New();
  progress->SetMiniPipelineFilter(this);
  progress->RegisterInternalFilter(m_IsoContourFilter, 0.5f);
  progress->RegisterInternalFilter(m_ChamferFilter, 0.5f);

  // Set up the isocontour filter
  m_IsoContourFilter->SetInput(this->GetInput());
  m_IsoContourFilter->SetFarValue(maximumDistance + 1);
  m_IsoContourFilter->SetNumberOfWorkUnits(numberOfWorkUnits);
  typename IsoContourType::PixelRealType levelSetValue =
    (static_cast<typename IsoContourType::PixelRealType>(m_InsideValue) +
     static_cast<typename IsoContourType::PixelRealType>(m_OutsideValue)) /
    2.0;
  m_IsoContourFilter->SetLevelSetValue(levelSetValue);

  // Set up the chamfer filter
  m_ChamferFilter->SetInput(m_IsoContourFilter->GetOutput());
  m_ChamferFilter->SetMaximumDistance(maximumDistance);
  m_ChamferFilter->SetNumberOfWorkUnits(numberOfWorkUnits);

  // Graft our output to the chamfer filter to force the proper regions
  // to be generated
  m_ChamferFilter->GraftOutput(output);

  // Create the distance map
  m_ChamferFilter->Update();

  // Graft the output of the chamfer filter back onto this filter's
  // output. this is needed to get the appropriate regions passed
  // back.
  this->GraftOutput(m_ChamferFilter->GetOutput());

  // Recall that we set the isocontour value to halfway between the inside and
  // outside value. The above filters assume that regions "inside" objects are
  // those with values *less* than the isocontour. This assumption is violated
  // if the "inside" intensity value is greater than the "outside" value.
  // (E.g. in the case that we're computing the distance from a mask where the
  // background is zero and the objects are colored 255.)
  // In this case, the distance will be calculated negative, so we need to
  // flip the sign of the output image.
  if (m_InsideValue > m_OutsideValue)
  {
    for (ImageScanlineIterator ot(output, oRegion); !ot.IsAtEnd(); ot.NextLine())
    {
      while (!ot.IsAtEndOfLine())
      {
        ot.Set(ot.Get() * -1);
        ++ot;
      }
    }
  }
}

template <typename TInputImage, typename TOutputImage>
void
ApproximateSignedDistanceMapImageFilter<TInputImage, TOutputImage>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);

  os << indent << "Inside intensity value: " << m_InsideValue << std::endl;
  os << indent << "Outside intensity value: " << m_OutsideValue << std::endl;
  os << indent << "IsoContourDistanceImageFilter (used internally): " << m_IsoContourFilter << std::endl;
  os << indent << "FastChamferDistanceImageFilter (used internally): " << m_ChamferFilter << std::endl;
}
} // end of namespace itk

#endif
