mirror of
https://gitlab.kitware.com/vtk/vtk-m
synced 2024-09-08 13:23:51 +00:00
128 lines
3.3 KiB
C++
128 lines
3.3 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_filter_ImageMedian_hxx
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#define vtk_m_filter_ImageMedian_hxx
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#include <vtkm/Swap.h>
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#include <vtkm/worklet/WorkletPointNeighborhood.h>
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namespace vtkm
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{
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namespace worklet
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{
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// An implementation of the quickselect/Hoare's selection algorithm to find medians
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// inplace, generally fairly fast for reasonable sized data.
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//
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template <typename T>
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VTKM_EXEC inline T find_median(T* values, std::size_t mid, std::size_t size)
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{
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std::size_t begin = 0;
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std::size_t end = size - 1;
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while (begin < end)
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{
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T x = values[mid];
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std::size_t i = begin;
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std::size_t j = end;
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do
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{
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for (; values[i] < x; i++)
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{
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}
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for (; x < values[j]; j--)
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{
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}
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if (i <= j)
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{
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vtkm::Swap(values[i], values[j]);
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i++;
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j--;
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}
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} while (i <= j);
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begin = (j < mid) ? i : begin;
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end = (mid < i) ? j : end;
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}
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return values[mid];
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}
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struct ImageMedian : public vtkm::worklet::WorkletPointNeighborhood
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{
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int Neighborhood;
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ImageMedian(int neighborhoodSize)
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: Neighborhood(neighborhoodSize)
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{
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}
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using ControlSignature = void(CellSetIn, FieldInNeighborhood, FieldOut);
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using ExecutionSignature = void(_2, _3);
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template <typename InNeighborhoodT, typename T>
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VTKM_EXEC void operator()(const InNeighborhoodT& input, T& out) const
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{
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vtkm::Vec<T, 25> values;
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int index = 0;
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for (int x = -this->Neighborhood; x <= this->Neighborhood; ++x)
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{
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for (int y = -this->Neighborhood; y <= this->Neighborhood; ++y)
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{
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values[index++] = input.Get(x, y, 0);
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}
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}
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std::size_t len =
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static_cast<std::size_t>((this->Neighborhood * 2 + 1) * (this->Neighborhood * 2 + 1));
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std::size_t mid = len / 2;
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out = find_median(&values[0], mid, len);
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}
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};
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}
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namespace filter
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{
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template <typename T, typename StorageType, typename DerivedPolicy>
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inline VTKM_CONT vtkm::cont::DataSet ImageMedian::DoExecute(
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const vtkm::cont::DataSet& input,
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const vtkm::cont::ArrayHandle<T, StorageType>& field,
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const vtkm::filter::FieldMetadata& fieldMetadata,
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const vtkm::filter::PolicyBase<DerivedPolicy>& policy)
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{
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if (!fieldMetadata.IsPointField())
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{
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throw vtkm::cont::ErrorBadValue("Active field for ImageMedian must be a point field.");
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}
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const vtkm::cont::DynamicCellSet& cells = input.GetCellSet();
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vtkm::cont::ArrayHandle<T> result;
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if (this->Neighborhood == 1 || this->Neighborhood == 2)
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{
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this->Invoke(worklet::ImageMedian{ this->Neighborhood },
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vtkm::filter::ApplyPolicyCellSetStructured(cells, policy, *this),
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field,
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result);
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}
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else
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{
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throw vtkm::cont::ErrorBadValue("ImageMedian only support a 3x3 or 5x5 stencil.");
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}
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std::string name = this->GetOutputFieldName();
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if (name.empty())
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{
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name = fieldMetadata.GetName();
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}
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return CreateResult(input, fieldMetadata.AsField(name, result));
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}
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}
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}
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#endif
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