OpenCV: contourArea assertion failed - c++

Question

when I try to start my application it crashes unexpectedly while executing contourArea.
Here is the error:
OpenCV Error: Assertion Failed (contour.checkVector(2) >= 0 && (contour.depth() ==CV_32F || contour.depth() == CV_32S)) in unknown function, file ..\..\..\src\opencv\modules\imgproc\src\contours.cpp, line 1904
My program is simple:
1.catch frame from camera,
2. gaussian and median filtering,
3. morphological opening,
4. threshold,
5. findContours,
6. draw the contourn with bigger area
Here is my code:
#include <opencv2/opencv.hpp>
#include <stdio.h>
using namespace cv;
using namespace std;
Mat mask(480,640, CV_8UC1);
vector<Vec4i> hierarchy;
vector<vector<Point> > contours;
vector<Point> my_contourn;
int main(){
VideoCapture camera(0);
if(!camera.isOpened()){
return -1;
}
while(1){
Mat cameraframe,filtered_img,mask2;
camera >> cameraframe;
GaussianBlur(cameraframe,filtered_img,Size(11,11),0,0);
medianBlur(filtered_img,filtered_img,11);
cvtColor(filtered_img,filtered_img,CV_BGR2HSV);
inRange(filtered_img, Scalar(0, 76, 97), Scalar(20, 143, 205), mask);
morphologyEx(mask,mask,MORPH_OPEN,getStructuringElement(MORPH_RECT,Size(9,9),Point(4,4)));
GaussianBlur(mask,mask,Size(3,3),0,0);
dilate(mask,mask,getStructuringElement(MORPH_ELLIPSE,Size(7, 7),Point(0, 0) ));
mask.copyTo(mask2);
findContours(mask2,contours,hierarchy,CV_RETR_EXTERNAL,CV_CHAIN_APPROX_SIMPLE,Point(0, 0));
double area,max_area=0.0;
for(int i=0;i<contours.size();i++){
area = fabs(contourArea(contours[i]));
if (area>max_area)
{
max_area=area;
my_contourn=contours[i];
}
}
drawContours( mask, my_contourn, 10, Scalar(255,0,0), 2, 8);
imshow("my cont",mask);
if(waitKey(30)>=0)
break;
}
return 0;
}
How I can fix it??

Answer 1

I confirm that is a VS2012 problem. On VS2010 everythings is fine.

Answer 2

This wierd bug also occurs on VS2013.
Try converting the type of contours[i] from vector to CV::Mat before pass it to contourArea.
Mat conMat(contours[i].size(), 2, CV_32FC1);
for(int i = 0; i < contours[i].size(); i ++)
{
conMat.at<float>(i, 0) = contours[i].x;
conMat.at<float>(i, 1) = contours[i].y;
}
area = fabs(contourArea(conMat));
That works for me.