From 12383a124be9bd9a5d8d7b8a14fa99ecf2c7a0f0 Mon Sep 17 00:00:00 2001
From: Vladislav Sovrasov <sovrasov.vlad@gmail.com>
Date: Mon, 5 Dec 2016 14:26:15 +0300
Subject: [PATCH] Disable error throwing in convexityDefects when hull is a
 line or point

---
 modules/imgproc/src/convhull.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/modules/imgproc/src/convhull.cpp b/modules/imgproc/src/convhull.cpp
index f7e7c2291d..1f8ef7b44b 100644
--- a/modules/imgproc/src/convhull.cpp
+++ b/modules/imgproc/src/convhull.cpp
@@ -280,11 +280,16 @@ void convexityDefects( InputArray _points, InputArray _hull, OutputArray _defect
 
     Mat hull = _hull.getMat();
     int hpoints = hull.checkVector(1, CV_32S);
-    CV_Assert( hpoints > 2 );
+    CV_Assert( hpoints > 0 );
 
     const Point* ptr = points.ptr<Point>();
     const int* hptr = hull.ptr<int>();
     std::vector<Vec4i> defects;
+    if ( hpoints < 3 ) //if hull consists of one or two points, contour is always convex
+    {
+        _defects.release();
+        return;
+    }
 
     // 1. recognize co-orientation of the contour and its hull
     bool rev_orientation = ((hptr[1] > hptr[0]) + (hptr[2] > hptr[1]) + (hptr[0] > hptr[2])) != 2;