NumCpp  2.11.0
A Templatized Header Only C++ Implementation of the Python NumPy Library
gaussianFilter1d.hpp
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1 #pragma once
29 
30 #include <cmath>
31 #include <string>
32 
34 #include "NumCpp/Core/Types.hpp"
37 #include "NumCpp/NdArray.hpp"
39 
40 namespace nc::filter
41 {
42  //============================================================================
43  // Method Description:
55  template<typename dtype>
57  double inSigma,
58  Boundary inBoundaryType = Boundary::REFLECT,
59  dtype inConstantValue = 0)
60  {
61  if (inSigma <= 0)
62  {
63  THROW_INVALID_ARGUMENT_ERROR("input sigma value must be greater than zero.");
64  }
65 
66  // calculate the kernel size based off of the input sigma value
67  constexpr uint32 MIN_KERNEL_SIZE = 5;
68  uint32 kernelSize =
69  std::max(static_cast<uint32>(std::ceil(inSigma * 2. * 4.)), MIN_KERNEL_SIZE); // 4 standard deviations
70  if (kernelSize % 2 == 0)
71  {
72  ++kernelSize; // make sure the kernel is an odd size
73  }
74 
75  const auto kernalHalfSize = static_cast<double>(kernelSize / 2); // integer division
76 
77  // calculate the gaussian kernel
78  NdArray<double> kernel(1, kernelSize);
79  for (double i = 0; i < kernelSize; ++i)
80  {
81  kernel[static_cast<uint32>(i)] = utils::gaussian1d(i - kernalHalfSize, 0., inSigma);
82  }
83 
84  // normalize the kernel
85  kernel /= kernel.sum().item();
86 
87  // perform the convolution
88  NdArray<dtype> output =
89  convolve1d(inImageArray.template astype<double>(), kernel, inBoundaryType, inConstantValue)
90  .template astype<dtype>();
91 
92  return output;
93  }
94 } // namespace nc::filter
#define THROW_INVALID_ARGUMENT_ERROR(msg)
Definition: Error.hpp:37
Holds 1D and 2D arrays, the main work horse of the NumCpp library.
Definition: NdArrayCore.hpp:138
value_type item() const
Definition: NdArrayCore.hpp:2975
self_type sum(Axis inAxis=Axis::NONE) const
Definition: NdArrayCore.hpp:4571
Definition: addBoundary1d.hpp:44
NdArray< dtype > convolve1d(const NdArray< dtype > &inImageArray, const NdArray< dtype > &inWeights, Boundary inBoundaryType=Boundary::REFLECT, dtype inConstantValue=0)
Definition: convolve1d.hpp:54
NdArray< dtype > gaussianFilter1d(const NdArray< dtype > &inImageArray, double inSigma, Boundary inBoundaryType=Boundary::REFLECT, dtype inConstantValue=0)
Definition: gaussianFilter1d.hpp:56
Boundary
Boundary condition to apply to the image filter.
Definition: Boundary.hpp:36
double gaussian1d(double inX, double inMu, double inSigma) noexcept
Definition: gaussian1d.hpp:46
dtype ceil(dtype inValue) noexcept
Definition: ceil.hpp:48
NdArray< dtype > max(const NdArray< dtype > &inArray, Axis inAxis=Axis::NONE)
Definition: max.hpp:44
std::uint32_t uint32
Definition: Types.hpp:40