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/*
* Copyright (c) 2020-2021 Vasile Vilvoiu <vasi@vilvoiu.ro>
*
* specgram is free software; you can redistribute it and/or modify
* it under the terms of the MIT license. See LICENSE for details.
*/
#ifndef _WINDOW_FUNCTION_HPP_
#define _WINDOW_FUNCTION_HPP_
#include "input-parser.hpp"
#include <vector>
#include <complex>
#include <memory>
/**
* Types of supported window functions
*/
enum class WindowFunctionType {
kNone,
kHann,
kHamming,
kBlackman,
kNuttall
};
/**
* Base window function class.
*/
class WindowFunction {
protected:
const std::size_t window_size_; /* size of window */
std::vector<double> cached_factors_; /* precomputed factors for each element in window */
/**
* @param window_size Window size.
*/
explicit WindowFunction(std::size_t window_size);
public:
WindowFunction() = delete;
/**
* Apply function to a window.
* @param window Array of complex numbers.
* @return Element-wise multiplication between window and precomputed factors.
*/
ComplexWindow Apply(const ComplexWindow& window) const;
/**
* Build a fitting window function.
* @param type One of WindowFunctionType
* @param window_size Size of window.
* @return New WindowFunction instance.
*/
static std::unique_ptr<WindowFunction> Build(WindowFunctionType type, std::size_t window_size);
};
/**
* Specialization for generalized cosine window functions.
*/
class GeneralizedCosineWindowFunction : public WindowFunction {
protected:
public:
/**
* @param window_size Window size.
* @param a List of coefficients.
*/
GeneralizedCosineWindowFunction(std::size_t window_size, const std::vector<double>& a);
};
/**
* Specialization for Hann windows.
*/
class HannWindowFunction : public GeneralizedCosineWindowFunction {
public:
explicit HannWindowFunction(std::size_t window_size);
};
/**
* Specialization for Hamming windows.
*/
class HammingWindowFunction : public GeneralizedCosineWindowFunction {
public:
explicit HammingWindowFunction(std::size_t window_size);
};
/**
* Specialization for Blackman windows.
*/
class BlackmanWindowFunction : public GeneralizedCosineWindowFunction {
public:
explicit BlackmanWindowFunction(std::size_t window_size);
};
/**
* Specialization for Nuttall windows.
*/
class NuttallWindowFunction : public GeneralizedCosineWindowFunction {
public:
explicit NuttallWindowFunction(std::size_t window_size);
};
#endif
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