lowpassFilter.hpp

/*
 * Copyright (c) 2006-2016, Visualization and Multimedia Lab,
 *                          University of Zurich <http://vmml.ifi.uzh.ch>,
 *                          Eyescale Software GmbH,
 *                          Blue Brain Project, EPFL
 *
 * This file is part of VMMLib <https://github.com/VMML/vmmlib/>
 *
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 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.  Redistributions in binary
 * form must reproduce the above copyright notice, this list of conditions and
 * the following disclaimer in the documentation and/or other materials provided
 * with the distribution.  Neither the name of the Visualization and Multimedia
 * Lab, University of Zurich nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 */

/* @author Jafet Villafranca
 *
 * Implements low pass filtering on a templated data type, which needs to
 * implement multiplication by a scalar float for smoothing
 */

#ifndef __VMML__LOWPASS_FILTER__HPP__
#define __VMML__LOWPASS_FILTER__HPP__

#include <deque>

namespace vmml
{
template <size_t M, typename T>
class LowpassFilter
{
public:
    LowpassFilter(const float F)
        : _smoothFactor(F)
    {
    }
    ~LowpassFilter() {}
    const T& get() const { return _value; }
    const T* operator->() const { return &_value; }
    const T& operator*() const { return _value; }
    const T& add(const T& value);

private:
    std::deque<T> _data;
    float _smoothFactor;
    T _value;
};

template <size_t M, typename T>
const T& LowpassFilter<M, T>::add(const T& value)
{
    _data.push_front(value);

    while (_data.size() > M)
        _data.pop_back();

    // update
    typename std::deque<T>::const_iterator i = _data.begin();
    _value = *i;
    double weight = _smoothFactor;

    for (++i; i != _data.end(); ++i)
    {
        _value = _value * (1 - weight) + (*i) * weight;
        weight *= _smoothFactor;
    }

    return _value;
}

} // namespace vmml

#endif