fixed crashes in camshiftdemo (ticket #875)

modules/video/src/camshift.cpp

@@ -90,6 +90,13 @@ cvMeanShift( const void* imgProb, CvRect windowIn,
         int dx, dy, nx, ny;
         double inv_m00;
         cur_rect = cv::Rect(cur_rect) & cv::Rect(0, 0, mat->cols, mat->rows);
+        if( cv::Rect(cur_rect) == cv::Rect() )
+        {
+            cur_rect.x = mat->cols/2;
+            cur_rect.y = mat->rows/2;
+        }
+        cur_rect.width = MAX(cur_rect.width, 1);
+        cur_rect.height = MAX(cur_rect.height, 1);
         
         cvGetSubRect( mat, &cur_win, cur_rect ); 
         cvMoments( &cur_win, &moments );

samples/cpp/camshiftdemo.cpp

@@ -22,6 +22,7 @@ void help()
         "\tc - stop the tracking\n"
         "\tb - switch to/from backprojection view\n"
         "\th - show/hide object histogram\n"
+        "\tp - pause video\n"
         "To initialize tracking, select the object with mouse\n" << endl;
 }
 
@@ -87,23 +88,29 @@ int main( int argc, char** argv )
 
     help();
 
-    namedWindow( "Histogram", 1 );
-    namedWindow( "CamShift Demo", 1 );
+    namedWindow( "Histogram", 0 );
+    namedWindow( "CamShift Demo", 0 );
     setMouseCallback( "CamShift Demo", onMouse, 0 );
     createTrackbar( "Vmin", "CamShift Demo", &vmin, 256, 0 );
     createTrackbar( "Vmax", "CamShift Demo", &vmax, 256, 0 );
     createTrackbar( "Smin", "CamShift Demo", &smin, 256, 0 );
 
-    Mat hsv, hue, mask, hist, histimg = Mat::zeros(200, 320, CV_8UC3), backproj;
+    Mat frame, hsv, hue, mask, hist, histimg = Mat::zeros(200, 320, CV_8UC3), backproj;
+    bool paused = false;
     
     for(;;)
     {
-        Mat frame;
+        if( !paused )
+        {
             cap >> frame;
             if( frame.empty() )
                 break;
+        }
 
         frame.copyTo(image);
+        
+        if( !paused )
+        {
             cvtColor(image, hsv, CV_BGR2HSV);
 
             if( trackObject )
@@ -145,11 +152,21 @@ int main( int argc, char** argv )
                 backproj &= mask;
                 RotatedRect trackBox = CamShift(backproj, trackWindow,
                                     TermCriteria( CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1 ));
+                if( trackWindow.area() <= 1 )
+                {
+                    int cols = backproj.cols, rows = backproj.rows, r = (MIN(cols, rows) + 5)/6;
+                    trackWindow = Rect(trackWindow.x - r, trackWindow.y - r,
+                                       trackWindow.x + r, trackWindow.y + r) &
+                                  Rect(0, 0, cols, rows);
+                }
 
                 if( backprojMode )
                     cvtColor( backproj, image, CV_GRAY2BGR );
                 ellipse( image, trackBox, Scalar(0,0,255), 3, CV_AA );
             }
+        }
+        else if( trackObject < 0 )
+            paused = false;
 
         if( selectObject && selection.width > 0 && selection.height > 0 )
         {
@@ -179,6 +196,9 @@ int main( int argc, char** argv )
             else
                 namedWindow( "Histogram", 1 );
             break;
+        case 'p':
+            paused = !paused;
+            break;
         default:
             ;
         }