rankFilter.hpp

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#pragma once
 
#include <string>
 
#include "NumCpp/Core/Internal/Error.hpp"
#include "NumCpp/Core/Shape.hpp"
#include "NumCpp/Core/Slice.hpp"
#include "NumCpp/Core/Types.hpp"
#include "NumCpp/Filter/Boundaries/Boundaries2d/addBoundary2d.hpp"
#include "NumCpp/Functions/sort.hpp"
#include "NumCpp/NdArray.hpp"
 
namespace nc::filter
{
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<dtype> rankFilter(const NdArray<dtype>& inImageArray,
                              uint32                inSize,
                              uint32                inRank,
                              Boundary              inBoundaryType  = Boundary::REFLECT,
                              dtype                 inConstantValue = 0)
    {
        if (inRank >= utils::sqr(inSize))
        {
            THROW_INVALID_ARGUMENT_ERROR("rank not within filter footprint size.");
        }
 
        NdArray<dtype> arrayWithBoundary =
            boundary::addBoundary2d(inImageArray, inBoundaryType, inSize, inConstantValue);
        NdArray<dtype> output(inImageArray.shape());
 
        const Shape  inShape      = inImageArray.shape();
        const uint32 boundarySize = inSize / 2; // integer division
        const uint32 endPointRow  = boundarySize + inShape.rows;
        const uint32 endPointCol  = boundarySize + inShape.cols;
 
        for (uint32 row = boundarySize; row < endPointRow; ++row)
        {
            for (uint32 col = boundarySize; col < endPointCol; ++col)
            {
                NdArray<dtype> window = arrayWithBoundary(Slice(row - boundarySize, row + boundarySize + 1),
                                                          Slice(col - boundarySize, col + boundarySize + 1));
 
                output(row - boundarySize, col - boundarySize) = sort(window)[inRank];
            }
        }
 
        return output;
    }
} // namespace nc::filter