From b3bbe7704d160ca9678b57dc17c4a9074122fdfd Mon Sep 17 00:00:00 2001
From: Pavel Rojtberg <pavel.rojtberg@igd.fraunhofer.de>
Date: Wed, 23 Dec 2015 13:06:56 +0100
Subject: [PATCH] add jaccardDistance measure for rectangle overlap

computes the complement of the Jaccard Index as described in
https://en.wikipedia.org/wiki/Jaccard_index. For rectangles this reduces
to computing the intersection over the union.
---
 modules/core/include/opencv2/core/types.hpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/modules/core/include/opencv2/core/types.hpp b/modules/core/include/opencv2/core/types.hpp
index e166556af7..6909676dc3 100644
--- a/modules/core/include/opencv2/core/types.hpp
+++ b/modules/core/include/opencv2/core/types.hpp
@@ -51,6 +51,7 @@
 #include <climits>
 #include <cfloat>
 #include <vector>
+#include <limits>
 
 #include "opencv2/core/cvdef.h"
 #include "opencv2/core/cvstd.hpp"
@@ -1832,7 +1833,26 @@ Rect_<_Tp> operator | (const Rect_<_Tp>& a, const Rect_<_Tp>& b)
     return c |= b;
 }
 
+/**
+ * @brief measure dissimilarity between two sample sets
+ *
+ * computes the complement of the Jaccard Index as described in <https://en.wikipedia.org/wiki/Jaccard_index>.
+ * For rectangles this reduces to computing the intersection over the union.
+ */
+template<typename _Tp> static inline
+double jaccardDistance(const Rect_<_Tp>& a, const Rect_<_Tp>& b) {
+    _Tp Aa = a.area();
+    _Tp Ab = b.area();
 
+    if ((Aa + Ab) <= std::numeric_limits<_Tp>::epsilon()) {
+        // jaccard_index = 1 -> distance = 0
+        return 0.0;
+    }
+
+    double Aab = (a & b).area();
+    // distance = 1 - jaccard_index
+    return 1.0 - Aab / (Aa + Ab - Aab);
+}
 
 ////////////////////////////// RotatedRect //////////////////////////////