modified farneback sample to use T-API

samples/cpp/fback.cpp

@@ -37,7 +37,8 @@ int main(int, char**)
     if( !cap.isOpened() )
         return -1;
 
-    Mat prevgray, gray, flow, cflow, frame;
+    Mat flow, cflow, frame;
+    UMat gray, prevgray, uflow;
     namedWindow("flow", 1);
 
     for(;;)
@@ -45,10 +46,11 @@ int main(int, char**)
         cap >> frame;
         cvtColor(frame, gray, COLOR_BGR2GRAY);
 
-        if( prevgray.data )
+        if( !prevgray.empty() )
         {
-            calcOpticalFlowFarneback(prevgray, gray, flow, 0.5, 3, 15, 3, 5, 1.2, 0);
+            calcOpticalFlowFarneback(prevgray, gray, uflow, 0.5, 3, 15, 3, 5, 1.2, 0);
             cvtColor(prevgray, cflow, COLOR_GRAY2BGR);
+            uflow.copyTo(flow);
             drawOptFlowMap(flow, cflow, 16, 1.5, Scalar(0, 255, 0));
             imshow("flow", cflow);
         }