# HG changeset patch
# User Chris Cannam
# Date 1396875879 -3600
# Node ID a82362d501442e10c5b7583a64c57bc08e6e27da
# Parent  36bcde3c13d8112fa7a51b19e37d638b8440ea76
Median filter standalone method, and tests

diff -r 36bcde3c13d8 -r a82362d50144 maths/MedianFilter.h
--- a/maths/MedianFilter.h	Mon Apr 07 13:43:48 2014 +0100
+++ b/maths/MedianFilter.h	Mon Apr 07 14:04:39 2014 +0100
@@ -20,6 +20,7 @@
 #include <cassert>
 #include <cmath>
 #include <iostream>
+#include <vector>
 
 template <typename T>
 class MedianFilter
@@ -70,6 +71,21 @@
 	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;
diff -r 36bcde3c13d8 -r a82362d50144 tests/TestMedianFilter.cpp
--- a/tests/TestMedianFilter.cpp	Mon Apr 07 13:43:48 2014 +0100
+++ b/tests/TestMedianFilter.cpp	Mon Apr 07 14:04:39 2014 +0100
@@ -92,6 +92,85 @@
     BOOST_CHECK_EQUAL(f.get(), 7);
 }
 
+BOOST_AUTO_TEST_CASE(oddStandalone)
+{
+    // The standalone (static filter() method) function is intended to
+    // match e.g. MATLAB median filter, filtering a row at once
+    // assuming the values beyond its edges are zeroes. This basically
+    // just means it needs to compensate for the latency in the raw
+    // filter:
+    //
+    // Raw filter
+    //    1 3 5 7   ->   0 1 3 5    (N=3)
+    // (because at each step only the values up to that step are
+    // available)
+    //
+    // Standalone function:
+    //    1 3 5 7   ->   1 3 5 5    (N=3)
+    
+    std::vector<double> in;
+    in.push_back(1);
+    in.push_back(3);
+    in.push_back(5);
+    in.push_back(7);
+
+    std::vector<double> out = MedianFilter<double>::filter(3, in);
+    BOOST_CHECK_EQUAL(out[0], 1);
+    BOOST_CHECK_EQUAL(out[1], 3);
+    BOOST_CHECK_EQUAL(out[2], 5);
+    BOOST_CHECK_EQUAL(out[3], 5);
+}
+
+BOOST_AUTO_TEST_CASE(evenStandalone)
+{
+    // See above. But note that the even length does not match the
+    // MATLAB because it doesn't halve the middle, as MATLAB does
+
+    std::vector<double> in;
+    in.push_back(1);
+    in.push_back(3);
+    in.push_back(5);
+    in.push_back(7);
+
+    std::vector<double> out = MedianFilter<double>::filter(4, in);
+    BOOST_CHECK_EQUAL(out[0], 3);
+    BOOST_CHECK_EQUAL(out[1], 5);
+    BOOST_CHECK_EQUAL(out[2], 5);
+    BOOST_CHECK_EQUAL(out[3], 5);
+}
+
+BOOST_AUTO_TEST_CASE(standaloneEmpty)
+{
+    std::vector<double> in;
+    std::vector<double> out1 = MedianFilter<double>::filter(3, in);
+    BOOST_CHECK_EQUAL(out1.size(), 0);
+    std::vector<double> out2 = MedianFilter<double>::filter(4, in);
+    BOOST_CHECK_EQUAL(out2.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(types)
+{
+    MedianFilter<double> dfilt(3);
+    dfilt.push(1.2);
+    BOOST_CHECK_EQUAL(dfilt.get(), 0.0);
+    dfilt.push(2.4);
+    BOOST_CHECK_EQUAL(dfilt.get(), 1.2);
+    dfilt.push(1e-6);
+    BOOST_CHECK_EQUAL(dfilt.get(), 1.2);
+    dfilt.push(1e6);
+    BOOST_CHECK_EQUAL(dfilt.get(), 2.4);
+
+    MedianFilter<int> ifilt(3);
+    ifilt.push(1);
+    BOOST_CHECK_EQUAL(ifilt.get(), 0);
+    ifilt.push(2);
+    BOOST_CHECK_EQUAL(ifilt.get(), 1);
+    ifilt.push(0);
+    BOOST_CHECK_EQUAL(ifilt.get(), 1);
+    ifilt.push(1000);
+    BOOST_CHECK_EQUAL(ifilt.get(), 2);
+}
+
 BOOST_AUTO_TEST_SUITE_END()