From af2af3af9bf7735b8f4a08bf29e74c56d8623284 Mon Sep 17 00:00:00 2001
From: Vadim Pisarevsky <no@email>
Date: Tue, 31 May 2011 14:24:45 +0000
Subject: [PATCH] added KeyPoint::hash() (ticket #1100)

---
 .../include/opencv2/features2d/features2d.hpp     |  5 ++++-
 modules/features2d/src/keypoint.cpp               | 15 ++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/modules/features2d/include/opencv2/features2d/features2d.hpp b/modules/features2d/include/opencv2/features2d/features2d.hpp
index 3f339f135..98beda2b0 100644
--- a/modules/features2d/include/opencv2/features2d/features2d.hpp
+++ b/modules/features2d/include/opencv2/features2d/features2d.hpp
@@ -236,6 +236,9 @@ public:
             float _response=0, int _octave=0, int _class_id=-1)
             : pt(x, y), size(_size), angle(_angle),
             response(_response), octave(_octave), class_id(_class_id) {}
+    
+    size_t hash() const;
+    
     //! converts vector of keypoints to vector of points
     static void convert(const std::vector<KeyPoint>& keypoints,
                         CV_OUT std::vector<Point2f>& points2f,
@@ -257,7 +260,7 @@ public:
     CV_PROP_RW int octave; //!< octave (pyramid layer) from which the keypoint has been extracted
     CV_PROP_RW int class_id; //!< object class (if the keypoints need to be clustered by an object they belong to) 
 };
-
+    
 //! writes vector of keypoints to the file storage
 CV_EXPORTS void write(FileStorage& fs, const string& name, const vector<KeyPoint>& keypoints);
 //! reads vector of keypoints from the specified file storage node
diff --git a/modules/features2d/src/keypoint.cpp b/modules/features2d/src/keypoint.cpp
index 6f76026a5..21ebce277 100644
--- a/modules/features2d/src/keypoint.cpp
+++ b/modules/features2d/src/keypoint.cpp
@@ -43,7 +43,20 @@
 
 namespace cv
 {
-	
+
+size_t KeyPoint::hash() const
+{
+    size_t _Val = 2166136261U, scale = 16777619U;
+    Cv32suf u;
+    u.f = pt.x; _Val = (scale * _Val) ^ u.u;
+    u.f = pt.y; _Val = (scale * _Val) ^ u.u;
+    u.f = size; _Val = (scale * _Val) ^ u.u;
+    u.f = angle; _Val = (scale * _Val) ^ u.u;
+    u.f = response; _Val = (scale * _Val) ^ u.u;
+    _Val = (scale * _Val) ^ ((size_t) octave);
+    _Val = (scale * _Val) ^ ((size_t) class_id);
+    return _Val;
+}    
 
 void write(FileStorage& fs, const string& objname, const vector<KeyPoint>& keypoints)
 {