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/*=========================================================================
*
* 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 itkPathFunctions_h
#define itkPathFunctions_h
#include "itkChainCodePath.h"
#include "itkFourierSeriesPath.h"
#include <cmath>
namespace itk
{
/** Make a chain code trace another path of same dimensionality.
* If restrictMovement is true, then individual steps are allowed to move
* through only one dimension at a time; for 2D paths this results in an
* 8-connected chain code. */
template <typename TChainCodePath, typename TPathInput>
void
MakeChainCodeTracePath(TChainCodePath & chainPath, const TPathInput & inPath, bool restrictMovement = false)
{
using OffsetType = typename TChainCodePath::OffsetType;
using ChainInputType = typename TChainCodePath::InputType;
using InPathInputType = typename TPathInput::InputType;
OffsetType offset, tempOffset, zeroOffset;
InPathInputType inPathInput;
int dimension = OffsetType::GetOffsetDimension();
zeroOffset.Fill(0);
chainPath.Clear();
inPathInput = inPath.StartOfInput();
chainPath.SetStart(inPath.EvaluateToIndex(inPathInput));
for (ChainInputType chainInput = 0;;)
{
offset = inPath.IncrementInput(inPathInput);
if (zeroOffset == offset)
{
break;
}
if (!restrictMovement)
{
chainPath.InsertStep(chainInput++, offset);
}
else
{
for (int d = 0; d < dimension; ++d)
{
tempOffset.Fill(0);
tempOffset[d] = offset[d];
chainPath.InsertStep(chainInput++, tempOffset);
}
}
}
}
/** Make a Fourier series path trace a chain code path of same dimensionality.
* numHarmonics is the number of harmonics (frequency coefficients, which
* include the "DC" term) to compute. If chainPath has too few steps to
* calculate numHarmonics (due to the Nyquist criterion), then as many harmonics
* as possible (chainPath->NumberOfSteps()/2) will be calculated. No fewer than
* 2 harmonics will be calculated. */
template <typename TFourierSeriesPath, typename TChainCodePath>
void
MakeFourierSeriesPathTraceChainCode(TFourierSeriesPath & FSPath,
const TChainCodePath & chainPath,
unsigned int numHarmonics = 8)
{
using IndexType = typename TFourierSeriesPath::IndexType;
using OffsetType = typename TFourierSeriesPath::OffsetType;
using VectorType = typename TFourierSeriesPath::VectorType;
using FSInputType = typename TFourierSeriesPath::InputType;
using ChainInputType = typename TChainCodePath::InputType;
IndexType index;
VectorType indexVector;
VectorType cosCoefficient;
VectorType sinCoefficient;
FSInputType theta;
int dimension = OffsetType::GetOffsetDimension();
size_t numSteps = chainPath.NumberOfSteps();
const double PI = 4.0 * std::atan(1.0);
FSPath.Clear();
// Adjust our private copy of numHarmonics if necessary
if (numHarmonics <= 1)
{
numHarmonics = 2;
}
else if (numHarmonics * 2 > numSteps)
{
numHarmonics = numSteps / 2;
}
for (unsigned int n = 0; n < numHarmonics; ++n)
{
index = chainPath.GetStart();
cosCoefficient.Fill(0.0);
sinCoefficient.Fill(0.0);
for (ChainInputType step = 0; step < numSteps; ++step)
{
index += chainPath.Evaluate(step);
theta = 2 * n * PI * (static_cast<double>(step + 1)) / numSteps;
// turn the current index into a vector
for (int d = 0; d < dimension; ++d)
{
indexVector[d] = index[d];
}
cosCoefficient += indexVector * (std::cos(theta) / numSteps);
sinCoefficient += indexVector * (std::sin(theta) / numSteps);
}
FSPath.AddHarmonic(cosCoefficient, sinCoefficient);
}
}
} // end namespace itk
#endif
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