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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
QM DSP Library
Centre for Digital Music, Queen Mary, University of London.
This file Copyright 2010 Chris Cannam.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*/
#ifndef MEDIAN_FILTER_H
#define MEDIAN_FILTER_H
#include <algorithm>
#include <cassert>
#include <cmath>
#include <iostream>
#include <vector>
template <typename T>
class MedianFilter
{
public:
MedianFilter(int size, float percentile = 50.f) :
m_size(size),
m_frame(new T[size]),
m_sorted(new T[size]),
m_sortend(m_sorted + size - 1) {
setPercentile(percentile);
reset();
}
~MedianFilter() {
delete[] m_frame;
delete[] m_sorted;
}
void setPercentile(float p) {
m_index = int((m_size * p) / 100.f);
if (m_index >= m_size) m_index = m_size-1;
if (m_index < 0) m_index = 0;
}
void push(T value) {
if (value != value) {
std::cerr << "WARNING: MedianFilter::push: attempt to push NaN, pushing zero instead" << std::endl;
// we do need to push something, to maintain the filter length
value = T();
}
drop(m_frame[0]);
const int sz1 = m_size-1;
for (int i = 0; i < sz1; ++i) m_frame[i] = m_frame[i+1];
m_frame[m_size-1] = value;
put(value);
}
T get() const {
return m_sorted[m_index];
}
int getSize() const {
return m_size;
}
T getAt(float percentile) {
int ix = int((m_size * percentile) / 100.f);
if (ix >= m_size) ix = m_size-1;
if (ix < 0) ix = 0;
return m_sorted[ix];
}
void reset() {
for (int i = 0; i < m_size; ++i) m_frame[i] = 0;
for (int i = 0; i < m_size; ++i) m_sorted[i] = 0;
}
static std::vector<T> filter(int size, const std::vector<T> &in) {
std::vector<T> out;
MedianFilter<T> f(size);
for (int i = 0; i < int(in.size()); ++i) {
f.push(in[i]);
T median = f.get();
if (i >= size/2) out.push_back(median);
}
while (out.size() < in.size()) {
f.push(T());
out.push_back(f.get());
}
return out;
}
private:
const int m_size;
T *const m_frame;
T *const m_sorted;
T *const m_sortend;
int m_index;
void put(T value) {
// precondition: m_sorted contains m_size-1 values, packed at start
// postcondition: m_sorted contains m_size values, one of which is value
T *point = std::lower_bound(m_sorted, m_sortend, value);
const int n = m_sortend - point;
for (int i = n; i > 0; --i) point[i] = point[i-1];
*point = value;
}
void drop(T value) {
// precondition: m_sorted contains m_size values, one of which is value
// postcondition: m_sorted contains m_size-1 values, packed at start
T *point = std::lower_bound(m_sorted, m_sortend + 1, value);
if (*point != value) {
std::cerr << "WARNING: MedianFilter::drop: *point is " << *point
<< ", expected " << value << std::endl;
}
const int n = m_sortend - point;
for (int i = 0; i < n; ++i) point[i] = point[i+1];
*m_sortend = T(0);
}
MedianFilter(const MedianFilter &); // not provided
MedianFilter &operator=(const MedianFilter &); // not provided
};
#endif
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