text: /*=========================================================================
   *
   *  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
   *
   *         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 itkParametricPath_hxx
  #define itkParametricPath_hxx
  
  #include "itkParametricPath.h"
  #include "itkMath.h"
  
  namespace itk
  {
  /**
   * Constructor
   */
  template <unsigned int VDimension>
  ParametricPath<VDimension>::ParametricPath()
  {
    m_DefaultInputStepSize = 0.3;
  }
  
  template <unsigned int VDimension>
  auto
  ParametricPath<VDimension>::EvaluateToIndex(const InputType & input) const -> IndexType
  {
    ContinuousIndexType continuousIndex;
    IndexType           index;
  
    continuousIndex = this->Evaluate(input);
  
    // Round each coordinate to the nearest integer value
    for (unsigned int i = 0; i < VDimension; ++i)
    {
      index[i] = static_cast<IndexValueType>(continuousIndex[i] + 0.5);
    }
  
    return index;
  }
  
  template <unsigned int VDimension>
  auto
  ParametricPath<VDimension>::IncrementInput(InputType & input) const -> OffsetType
  {
    int        iterationCount;
    bool       tooSmall;
    bool       tooBig;
    InputType  inputStepSize;
    InputType  finalInputValue;
    OffsetType offset;
    IndexType  currentImageIndex;
    IndexType  nextImageIndex;
    IndexType  finalImageIndex;
  
    iterationCount = 0;
    inputStepSize = m_DefaultInputStepSize;
  
    // Are we already at (or past) the end of the input?
    finalInputValue = this->EndOfInput();
    currentImageIndex = this->EvaluateToIndex(input);
    finalImageIndex = this->EvaluateToIndex(finalInputValue);
    offset = finalImageIndex - currentImageIndex;
    if ((offset == this->GetZeroOffset() && Math::NotExactlyEquals(input, this->StartOfInput())) ||
        (input >= finalInputValue))
    {
      return this->GetZeroOffset();
    }
  
    do
    {
      if (iterationCount++ > 10000)
      {
        itkExceptionMacro(<< "Too many iterations");
      }
  
      nextImageIndex = this->EvaluateToIndex(input + inputStepSize);
      offset = nextImageIndex - currentImageIndex;
  
      tooBig = false;
      tooSmall = (offset == this->GetZeroOffset());
      if (tooSmall)
      {
        // double the input step size, but don't go past the end of the input
        inputStepSize *= 2;
        if ((input + inputStepSize) >= finalInputValue)
        {
          inputStepSize = finalInputValue - input;
        }
      }
      else
      {
        // Search for an offset dimension that is too big
        for (unsigned int i = 0; i < VDimension && !tooBig; ++i)
        {
          tooBig = (offset[i] >= 2 || offset[i] <= -2);
        }
  
        if (tooBig)
        {
          inputStepSize /= 1.5;
        }
      }
    } while (tooSmall || tooBig);
  
    input += inputStepSize;
    return offset;
  }
  
  template <unsigned int VDimension>
  auto
  ParametricPath<VDimension>::EvaluateDerivative(const InputType & input) const -> VectorType
  {
    InputType inputStepSize;
  
    inputStepSize = m_DefaultInputStepSize;
    if ((input + inputStepSize) >= this->EndOfInput())
    {
      inputStepSize = this->EndOfInput() - input;
    }
  
    return (this->Evaluate(input + inputStepSize) - this->Evaluate(input)) / inputStepSize;
  }
  
  template <unsigned int VDimension>
  void
  ParametricPath<VDimension>::PrintSelf(std::ostream & os, Indent indent) const
  {
    Superclass::PrintSelf(os, indent);
    os << indent << "DefaultInputSize: " << m_DefaultInputStepSize << std::endl;
  }
  } // namespace itk
  
  #endif
  