New feature to tracking sample

Now initial bounding frame can be given in command-line, as an alternative
to manual selection via mouse. Bounding frame is given as optional last
argument in the format "x1,y1,x2,y2" where x's and y's are integers,
symbolizing bounding box with opposite vertices (x1,y1) and (x2,y2).

modules/tracking/samples/tracker.cpp

@@ -15,7 +15,8 @@ static bool startSelection = false;
 static const char* keys =
 { "{@tracker_algorithm | | Tracker algorithm }"
     "{@video_name      | | video name        }"
-    "{@start_frame     |1| Start frame       }" };
+    "{@start_frame     |1| Start frame       }" 
+    "{@bounding_frame  |0,0,0,0| Initial bounding frame}"};
 
 static void help()
 {
@@ -23,7 +24,7 @@ static void help()
        "-- pause video [p] and draw a bounding box around the target to start the tracker\n"
        "Example of <video_name> is in opencv_extra/testdata/cv/tracking/\n"
        "Call:\n"
-       "./tracker <tracker_algorithm> <video_name> <start_frame>\n"
+       "./tracker <tracker_algorithm> <video_name> <start_frame> [<bounding_frame>]\n"
        << endl;
 
   cout << "\n\nHot keys: \n"
@@ -79,6 +80,33 @@ int main( int argc, char** argv )
     return -1;
   }
 
+  int coords[4]={0,0,0,0};
+  bool initFrameWasGivenInCommandLine=false;
+  do{
+      String initBoundingBox=parser.get<String>(3);
+      for(size_t pos=0,ctr=0;ctr<4;ctr++){
+        size_t npos=initBoundingBox.find_first_of(',',pos);
+        if(npos==string::npos && ctr<3){
+           printf("bounding box should be given in format \"x1,y1,x2,y2\",where x's and y's are integer cordinates of opposed corners of bdd box\n");
+           printf("got: %s\n",initBoundingBox.substr(pos,string::npos).c_str());
+           printf("manual selection of bounding box will be employed\n");
+           break;
+        }
+        int num=atoi(initBoundingBox.substr(pos,(ctr==3)?(string::npos):(npos-pos)).c_str());
+        if(num<=0){
+           printf("bounding box should be given in format \"x1,y1,x2,y2\",where x's and y's are integer cordinates of opposed corners of bdd box\n");
+           printf("got: %s\n",initBoundingBox.substr(pos,npos-pos).c_str());
+           printf("manual selection of bounding box will be employed\n");
+           break;
+        }
+        coords[ctr]=num;
+        pos=npos+1;
+      }
+      if(coords[0]>0 && coords[1]>0 && coords[2]>0 && coords[3]>0){
+          initFrameWasGivenInCommandLine=true;
+      }
+  }while(0);
+
   //open the capture
   VideoCapture cap;
   cap.open( video_name );
@@ -109,6 +137,16 @@ int main( int argc, char** argv )
   //get the first frame
   cap >> frame;
   frame.copyTo( image );
+  if(initFrameWasGivenInCommandLine){
+      selectObject=true;
+      paused=false;
+      boundingBox.x = coords[0];
+      boundingBox.y = coords[1];
+      boundingBox.width = std::abs( coords[2] - coords[0] );
+      boundingBox.height = std::abs( coords[3]-coords[1]);
+      printf("bounding box with vertices (%d,%d) and (%d,%d) was given in command line\n",coords[0],coords[1],coords[2],coords[3]);
+      rectangle( image, boundingBox, Scalar( 255, 0, 0 ), 2, 1 );
+  }
   imshow( "Tracking API", image );
 
   bool initialized = false;