opencv 3.0 findContours function not working in window - c++

Question

I am using visual studio 15 and working in opencv 3.0 ,i am getting access violation error in my code and even this function is not working with sample code given in opencv.
#include"stdafx.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <math.h>
#include <iostream>
using namespace cv;
using namespace std;
static void help()
{
cout
<< "\nThis program illustrates the use of findContours and drawContours\n"
<< "The original image is put up along with the image of drawn contours\n"
<< "Usage:\n"
<< "./contours2\n"
<< "\nA trackbar is put up which controls the contour level from -3 to 3\n"
<< endl;
}
const int w = 500;
int levels = 3;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
static void on_trackbar(int, void*)
{
Mat cnt_img = Mat::zeros(w, w, CV_8UC3);
int _levels = levels - 3;
drawContours(cnt_img, contours, _levels <= 0 ? 3 : -1, Scalar(128, 255, 255),
3, LINE_AA, hierarchy, std::abs(_levels));
imshow("contours", cnt_img);
}
int main(int argc, char**)
{
Mat img = Mat::zeros(w, w, CV_8UC1);
if (argc > 1)
{
help();
return -1;
}
//Draw 6 faces
for (int i = 0; i < 6; i++)
{
int dx = (i % 2) * 250 - 30;
int dy = (i / 2) * 150;
const Scalar white = Scalar(255);
const Scalar black = Scalar(0);
if (i == 0)
{
for (int j = 0; j <= 10; j++)
{
double angle = (j + 5)*CV_PI / 21;
line(img, Point(cvRound(dx + 100 + j * 10 - 80 * cos(angle)),
cvRound(dy + 100 - 90 * sin(angle))),
Point(cvRound(dx + 100 + j * 10 - 30 * cos(angle)),
cvRound(dy + 100 - 30 * sin(angle))), white, 1, 8, 0);
}
}
ellipse(img, Point(dx + 150, dy + 100), Size(100, 70), 0, 0, 360, white, -1, 8, 0);
ellipse(img, Point(dx + 115, dy + 70), Size(30, 20), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 185, dy + 70), Size(30, 20), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 115, dy + 70), Size(15, 15), 0, 0, 360, white, -1, 8, 0);
ellipse(img, Point(dx + 185, dy + 70), Size(15, 15), 0, 0, 360, white, -1, 8, 0);
ellipse(img, Point(dx + 115, dy + 70), Size(5, 5), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 185, dy + 70), Size(5, 5), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 150, dy + 100), Size(10, 5), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 150, dy + 150), Size(40, 10), 0, 0, 360, black, -1, 8, 0);
ellipse(img, Point(dx + 27, dy + 100), Size(20, 35), 0, 0, 360, white, -1, 8, 0);
ellipse(img, Point(dx + 273, dy + 100), Size(20, 35), 0, 0, 360, white, -1, 8, 0);
}
//show the faces
namedWindow("image", 1);
imshow("image", img);
//Extract the contours so that
//vector<vector<Point> > contours0;
vector<cv::Mat> coutours;
findContours(img, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE);
contours.resize(contours.size());
for (size_t k = 0; k < contours.size(); k++)
approxPolyDP(Mat(contours[k]), contours[k], 3, true);
namedWindow("contours", 1);
createTrackbar("levels+3", "contours", &levels, 7, on_trackbar);
on_trackbar(0, 0);
waitKey();
return 0;
}
I am using x64 architecture and linked all the library .lib along with d.lib(debug library).

Answer 1

I think the problem comes from your "contours" variable. You're declaring it as a vector<cv::Mat>, but the contours are not represented as a matrix, but rather as a series of points.
Look at this example : http://docs.opencv.org/2.4/doc/tutorials/imgproc/shapedescriptors/find_contours/find_contours.html
They declare the contours as vector<vector<Point> > contours;
Look also at the declaration of the function (http://docs.opencv.org/2.4/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=findcontours#findcontours), the paramater contour is defined as : contours – Detected contours. Each contour is stored as a vector of points.