fixed drawKeypoints (keypoint orientation)

modules/features2d/src/draw.cpp

@@ -67,8 +67,9 @@ static inline void _drawKeypoint( Mat& img, const KeyPoint& p, const Scalar& col
         if( p.angle != -1 )
         {
             float srcAngleRad = p.angle*(float)CV_PI/180.f;
-            Point orient(cvRound(cos(srcAngleRad)*radius), 
-						 cvRound(sin(srcAngleRad)*radius));
+            Point orient( cvRound( cos(srcAngleRad)*radius ),
+                          cvRound(-sin(srcAngleRad)*radius ) // "-" to invert orientation of axis y
+                        );
             line( img, center, center+orient, color, 1, CV_AA, draw_shift_bits );
         }
 #if 0