How would I integrate the contourArea() function in my OpenCV program? - c++

Question

My code is for the purposes of detecting various shapes based off the number of vertices they have. I've finally accomplished that and it works perfectly for simple images like shown here: http://i.imgur.com/f9qvBwF.png However for this thresh image: http://i.imgur.com/jhl0NUQ.png it creates hundreds of shapes because of all the little pixels. Now I know enough of OpenCV to know there's eroding and dilating, but it seems like the best approach would be to exclude contours whose area is below a certain pixel count, however I don't know how to integrate the contourArea() function into my code such that it would work.
Here is my current code:
#include "opencv2/core/core.hpp"
#include "opencv2/flann/miniflann.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/photo/photo.hpp"
#include "opencv2/video/video.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/ml/ml.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/contrib/contrib.hpp"
#include "opencv2/core/core_c.h"
#include "opencv2/highgui/highgui_c.h"
#include "opencv2/imgproc/imgproc_c.h"
using namespace cv;
using namespace std;
Mat img;
Mat img_gray;
void contour_finder(int, void*);
int main(int argc, char *argv[])
{
img = imread("C:/Users/wyndr_000/Documents/VisualStudio2013/Projects/OpenCV_Template/OpenCV_Template/testpic.png", CV_LOAD_IMAGE_UNCHANGED);
cvtColor(img, img_gray, CV_RGB2GRAY);
contour_finder(0, 0);
waitKey();
}
void contour_finder(int, void*)
{
Mat img_thresh;
Mat drawn_contours;
threshold(img_gray, img_thresh, 183, 255, 2);
imshow("Thresh Image", img_thresh);
vector<vector<Point> > contours;
vector<Point> result;
findContours(img_thresh, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
// Find a way to filter it out based on Area
for (size_t i = 0; i < contours.size(); i++){
approxPolyDP(Mat(contours[i]), result, arcLength(Mat(contours[i]), true)*0.02, true);
// if (contourArea(result) < 49)
//{
if (result.size() == 3)
{
cout << "TRIANGLE\n";
}
else if (result.size() == 4)
{
cout << "QUADRILATERAL\n";
}
else if (result.size() == 5)
{
cout << "PENTAGON\n";
}
else if (result.size() == 6)
{
cout << "HEXAGON\n";
}
else if (result.size() == 10)
{
cout << "STAR\n";
}
else if (result.size() == 12)
{
cout << "PLUS-SIGN\n";
}
// }
}
/* drawn_contours = Mat::zeros(img_thresh.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(drawn_contours, contours, i, color, 2, 8, hierarchy, 0, Point());
}
namedWindow("Contours", CV_WINDOW_AUTOSIZE);
imshow("Contours", drawn_contours); */
}
You'll notice where I declare what different amounts of vertices indicate, I have a commented contourArea function, because that's where I imagined it would go.