vector<vector<Point> > contours 'Unable to read memory error'

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Hi,

i'm developing on win 64bit, windows 7. OpenCV Version: opencv 2.4.3 C:\fakepath\contour.png

My contour points after running findContours function, the some vector points in the contours have a 'unable to read memory error'.

The code below is a sample code obtained from opencv samples.

Please help?

Mat src; Mat src_gray;
 int thresh = 100;
 int max_thresh = 255;
 RNG rng(12345);

 /// Function header
 void thresh_callback(int, void* );

int _tmain(int argc, _TCHAR* argv[])
{

    /// Load source image and convert it to gray
   src = imread( "D://Download - Software//1//1.2.840.113619.2.135.2025.1616282.5237.1221046207.476.jpg", 1 );

   /// Convert image to gray and blur it
   cvtColor( src, src_gray, CV_BGR2GRAY );
   blur( src_gray, src_gray, Size(3,3) );

   /// Create Window
   char* source_window = "Source";
   namedWindow( source_window, CV_WINDOW_AUTOSIZE );
   imshow( source_window, src );

   createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback );
   thresh_callback( 0, 0 );

   waitKey(0);
   return(0);
}

/** @function thresh_callback */
 void thresh_callback(int, void* )
 {
   Mat src_copy = src.clone();
   Mat threshold_output;
   vector<vector<Point> > contours;
   vector<Vec4i> hierarchy;

   /// Detect edges using Threshold
   threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );

   /// Find contours
   findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

   /// Find the convex hull object for each contour
   vector<vector<Point> >hull(contours.size() );
   for( int i = 0; i < contours.size(); i++ )
      {  convexHull( Mat(contours[i]), hull[i], false ); }

   /// Draw contours + hull results
   Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
   for( int i = 0; i< contours.size(); i++ )
      {
        Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
        drawContours( drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
        drawContours( drawing, hull, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
      }

   /// Show in a window
   namedWindow( "Hull demo", CV_WINDOW_AUTOSIZE );
   imshow( "Hull demo", drawing );
 }