changeset 164:4a70fff27b8f

Add median filter (originally from devuvuzelator code)

--- a/build/general/Makefile.inc	Thu Jan 30 09:51:06 2014 +0000
+++ b/build/general/Makefile.inc	Fri Apr 04 12:40:40 2014 +0100
@@ -46,6 +46,7 @@
            maths/KLDivergence.h \
            maths/MathAliases.h \
            maths/MathUtilities.h \
+	   maths/MedianFilter.h \
            maths/Polyfit.h \
            maths/pca/pca.h \
            thread/AsynchronousTask.h \

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/maths/MedianFilter.h	Fri Apr 04 12:40:40 2014 +0100
@@ -0,0 +1,91 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+#ifndef MEDIAN_FILTER_H
+#define MEDIAN_FILTER_H
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <iostream>
+
+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) return; // nan
+	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];
+    }
+
+    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;
+    }
+
+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);
+    }
+};
+
+#endif
+