Chris@153: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@153: 
Chris@153: /*
Chris@153:     QM DSP Library
Chris@153: 
Chris@153:     Centre for Digital Music, Queen Mary, University of London.
Chris@153:     This file Copyright 2010 Chris Cannam.
Chris@153: 
Chris@153:     This program is free software; you can redistribute it and/or
Chris@153:     modify it under the terms of the GNU General Public License as
Chris@153:     published by the Free Software Foundation; either version 2 of the
Chris@153:     License, or (at your option) any later version.  See the file
Chris@153:     COPYING included with this distribution for more information.
Chris@153: */
Chris@153: 
Chris@153: #ifndef MEDIAN_FILTER_H
Chris@153: #define MEDIAN_FILTER_H
Chris@153: 
Chris@153: #include <algorithm>
Chris@153: #include <cassert>
Chris@153: #include <cmath>
Chris@153: #include <iostream>
Chris@153: #include <vector>
Chris@153: 
Chris@153: template <typename T>
Chris@153: class MedianFilter
Chris@153: {
Chris@153: public:
Chris@153:     MedianFilter(int size, float percentile = 50.f) :
Chris@153: 	m_size(size),
Chris@153: 	m_frame(new T[size]),
Chris@153: 	m_sorted(new T[size]),
Chris@153: 	m_sortend(m_sorted + size - 1) {
Chris@153:         setPercentile(percentile);
Chris@153: 	reset();
Chris@153:     }
Chris@153: 
Chris@153:     ~MedianFilter() { 
Chris@153: 	delete[] m_frame;
Chris@153: 	delete[] m_sorted;
Chris@153:     }
Chris@153: 
Chris@153:     void setPercentile(float p) {
Chris@153:         m_index = int((m_size * p) / 100.f);
Chris@153:         if (m_index >= m_size) m_index = m_size-1;
Chris@153:         if (m_index < 0) m_index = 0;
Chris@153:     }
Chris@153: 
Chris@153:     void push(T value) {
Chris@371:         if (value != value) { // nan
Chris@371:             static bool warned = false;
Chris@371:             if (!warned) {
Chris@371:                 std::cerr << "WARNING: MedianFilter::push: attempt to push NaN" << std::endl;
Chris@371:                 std::cerr << "WARNING: MedianFilter::push: (only one warning will be printed)" << std::endl;
Chris@371:                 warned = true;
Chris@371:             }
Chris@371:             return;
Chris@153:         }
Chris@153: 	drop(m_frame[0]);
Chris@153: 	const int sz1 = m_size-1;
Chris@153: 	for (int i = 0; i < sz1; ++i) m_frame[i] = m_frame[i+1];
Chris@153: 	m_frame[m_size-1] = value;
Chris@153: 	put(value);
Chris@153:     }
Chris@153: 
Chris@153:     T get() const {
Chris@153: 	return m_sorted[m_index];
Chris@153:     }
Chris@153: 
Chris@153:     int getSize() const {
Chris@153:         return m_size; 
Chris@153:     }
Chris@153: 
Chris@153:     T getAt(float percentile) {
Chris@153: 	int ix = int((m_size * percentile) / 100.f);
Chris@153:         if (ix >= m_size) ix = m_size-1;
Chris@153:         if (ix < 0) ix = 0;
Chris@153: 	return m_sorted[ix];
Chris@153:     }
Chris@153: 
Chris@153:     void reset() {
Chris@153: 	for (int i = 0; i < m_size; ++i) m_frame[i] = 0;
Chris@153: 	for (int i = 0; i < m_size; ++i) m_sorted[i] = 0;
Chris@153:     }
Chris@153: 
Chris@153:     static std::vector<T> filter(int size, const std::vector<T> &in) {
Chris@153:         std::vector<T> out;
Chris@153:         MedianFilter<T> f(size);
Chris@153:         for (int i = 0; i < int(in.size()); ++i) {
Chris@153:             f.push(in[i]);
Chris@153:             T median = f.get();
Chris@153:             if (i >= size/2) out.push_back(median);
Chris@153:         }
Chris@153:         while (out.size() < in.size()) {
Chris@153:             f.push(T());
Chris@153:             out.push_back(f.get());
Chris@153:         }
Chris@153:         return out;
Chris@153:     }
Chris@153: 
Chris@153: private:
Chris@153:     const int m_size;
Chris@153:     T *const m_frame;
Chris@153:     T *const m_sorted;
Chris@153:     T *const m_sortend;
Chris@153:     int m_index;
Chris@153: 
Chris@153:     void put(T value) {
Chris@153: 	// precondition: m_sorted contains m_size-1 values, packed at start
Chris@153: 	// postcondition: m_sorted contains m_size values, one of which is value
Chris@153: 	T *point = std::lower_bound(m_sorted, m_sortend, value);
Chris@153: 	const int n = m_sortend - point;
Chris@153: 	for (int i = n; i > 0; --i) point[i] = point[i-1];
Chris@153: 	*point = value;
Chris@153:     }
Chris@153: 
Chris@153:     void drop(T value) {
Chris@153: 	// precondition: m_sorted contains m_size values, one of which is value
Chris@153: 	// postcondition: m_sorted contains m_size-1 values, packed at start
Chris@153: 	T *point = std::lower_bound(m_sorted, m_sortend + 1, value);
Chris@153: 	if (*point != value) {
Chris@153: 	    std::cerr << "WARNING: MedianFilter::drop: *point is " << *point
Chris@153: 		      << ", expected " << value << std::endl;
Chris@153: 	}
Chris@153: 	const int n = m_sortend - point;
Chris@153: 	for (int i = 0; i < n; ++i) point[i] = point[i+1];
Chris@153: 	*m_sortend = T(0);
Chris@153:     }
Chris@153: 
Chris@153:     MedianFilter(const MedianFilter &); // not provided
Chris@153:     MedianFilter &operator=(const MedianFilter &); // not provided
Chris@153: };
Chris@153: 
Chris@153: #endif
Chris@153: