Merge branch 4.x

modules/optflow/include/opencv2/optflow/rlofflow.hpp

@@ -227,6 +227,7 @@ public:
  * @note If the grid size is set to (1,1) and the forward backward threshold <= 0 than pixelwise dense optical flow field is
  * computed by RLOF without using interpolation.
  *
+ * @note Note that in output, if no correspondences are found between \a I0 and \a I1, the \a flow is set to 0.
  * @see optflow::calcOpticalFlowDenseRLOF(), optflow::RLOFOpticalFlowParameter
 */
 class CV_EXPORTS_W DenseRLOFOpticalFlow : public DenseOpticalFlow
@@ -493,6 +494,7 @@ public:
  * computed with the RLOF.
  *
  * @note SIMD parallelization is only available when compiling with SSE4.1.
+ * @note Note that in output, if no correspondences are found between \a I0 and \a I1, the \a flow is set to 0.
  *
  * @sa optflow::DenseRLOFOpticalFlow, optflow::RLOFOpticalFlowParameter
 */

modules/optflow/src/rlofflow.cpp

@@ -203,7 +203,11 @@ public:
             filtered_prevPoints = prevPoints;
             filtered_currPoints = currPoints;
         }
-
+        // Interpolators below expect non empty matches
+        if (filtered_prevPoints.empty()) {
+            flow.setTo(0);
+            return;
+        }
         if (interp_type == InterpolationType::INTERP_EPIC)
         {
             Ptr<ximgproc::EdgeAwareInterpolator> gd = ximgproc::createEdgeAwareInterpolator();

modules/optflow/src/tvl1flow.cpp

@@ -99,6 +99,8 @@ public:
     }
     OpticalFlowDual_TVL1();
 
+    virtual String getDefaultName() const CV_OVERRIDE { return "DenseOpticalFlow.DualTVL1OpticalFlow"; }
+
     void calc(InputArray I0, InputArray I1, InputOutputArray flow) CV_OVERRIDE;
     void collectGarbage() CV_OVERRIDE;