OpenCV c++ assertion failed <i < 0> in cv::_InputArray::getMat - c++

Question

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/video/background_segm.hpp>
#include <iostream>
#include <windows.h>
using namespace cv;
using namespace std;
//initial min and max HSV filter values.
//these will be changed using trackbars
Mat src; Mat HSV; Mat roi; Mat range; Mat eroded; Mat gray;
int thresh = 100;
int max_thresh = 255;
/** #function main */
int main(int argc, char** argv)
{
createTrackbars();
VideoCapture cap(0); // open the default camera
if (!cap.isOpened()) // check if we succeeded
return -1;
namedWindow("background", 1);
int waitTime = 50;
int counter = 101;
int roiLeft = 20;
int roiTop = 50;
int roiRight = 200;
int roiBottom = 200;
Rect rRoi = Rect(roiLeft, roiTop, roiRight, roiBottom);
Mat background;
cap >> background;
background = background(rRoi);
//cvtColor(background, background, CV_BGR2HSV);
//imshow("background", background);
vector<vector<Point> > contours;
vector<vector < cv::Point >> hull(1);
vector<Vec4i> hierarchy;
vector<CvConvexityDefect> defects;
while (true)
{
cap >> src;
//Create the region of interest.
Mat iRoi = src.clone()(rRoi);
Mat iRoiSRC = src(rRoi);
//Draw a rectangle there.
rectangle(src, rRoi, Scalar(255, 128, 0), 1, 8, 0);
//imshow("roi", iRoi);
//Subtract the static background.
absdiff(iRoi, background, iRoi);
//imshow("diff", iRoi);
//Convert it to a GrayScale and threshold it.
cvtColor(iRoi, iRoi, CV_BGR2GRAY);
threshold(iRoi, gray, 15, 255, CV_THRESH_BINARY);
//Perform a closing.
Mat erodeElement = getStructuringElement(MORPH_ELLIPSE, Size(erodeSize, erodeSize));
Mat dilateElement = getStructuringElement(MORPH_ELLIPSE, Size(dilateSize, dilateSize));
for (int index = 0; index < loopAmount; index++)
{
erode(gray, gray, erodeElement);
dilate(gray, gray, dilateElement);
}
//imshow("range", gray);
//Find the contours.
findContours(gray, contours, hierarchy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
//Pick the biggest contour.
int biggestContourIndex = 0;
int largestArea = 0;
for (int i = 0; i < contours.size(); i++)
{
if (contours[i].size() > largestArea)
{
largestArea = contours[i].size();
biggestContourIndex = i;
}
}
vector<int> hullsI;
vector<Point> hullsP;
vector<Vec4i> defects;
//Find the convex hull.
if (contours.size() > 0)
{
convexHull(contours[biggestContourIndex], hullsI, true, true);
convexHull(contours[biggestContourIndex], hullsP, true, true);
}
//Find the convexity defects.
if (contours.size() > 0)
{
if (contours[biggestContourIndex].size() > 3)
{
convexityDefects(contours[biggestContourIndex], hullsI, defects);
}
}
//Draw the biggest contour and its convex hull.
Scalar colorOne = Scalar(255, 128, 0);
Scalar colorTwo = Scalar(0, 0, 255);
if (contours.size() > 0)
{
drawContours(iRoiSRC, contours, biggestContourIndex, colorOne, 2, 8, hierarchy, 0, Point());
drawContours(iRoiSRC, hullsP, 0, colorTwo, 1, 8, vector<Vec4i>(), 0, Point());
rectangle(iRoiSRC, boundingRect(contours[biggestContourIndex]), Scalar(0, 255, 0), 1, 8, 0);
}
imshow("src", src);
if (waitKey(waitTime) >= 0) break;
}
return(0);
}
There is a rectangle in the upper left of the screen, where my hand will be recognized once I hold it there.
The error that i get appears at the first drawContours. The full error which is given to me by the console is: OpenCV Error: Assertion failed <i <0> in cv::_InputArray::getMat, file C:\buildslave64\win64_amdoc1\2_4_PackSlave-win64-vc11-shared\opencv\modules\core\src\matrix.cpp, line 963
I've been extensively searching for a solution on multiple sites, including stackoverflow but none of the solution seem to be working.
Any help would be appreciated.
I use Visual studio 2013 with OpenCV-2.4.10

Answer 1

converting vector<CvConvexityDefect> defects; to a point seemed to do the trick