How to obtain a contour from points with OpenCV - opencv

Question

I'm trying to obtain a ROI from an image using VC++ and OpenCV.
I managed to display an image, get the coordinates of a point when I click on it, store these coordinates in a vector and draw lines between these points on my image.
Here is my code:
//Includes
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <stdio.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace std;
using namespace cv;
static int app;
static vector<Point2f> cont(6);
static Mat img = imread("C:/img.jpg",0);
void on_mouse(int, int, int, int, void* );
int main()
{
app = 0;
namedWindow("myWindow", CV_WINDOW_AUTOSIZE);
cvSetMouseCallback("myWindow", on_mouse, 0);
imshow("myWindow", img);
waitKey(0);
}
void on_mouse(int evt, int x, int y, int flags, void* param)
{
if(evt == CV_EVENT_LBUTTONDOWN)
{
Point pt(x,y);
if(app<6)
{
cont[app]=pt;
app++;
}
cout<<"Coordonnees du point pt : "<<x<<","<<y<<endl;
for (int i=0; i<6;i++)
{cout<<cont[i]<<endl;}
}
if(evt == CV_EVENT_RBUTTONDOWN)
{
for (int j=0;j<5;j++)
{
line(img,cont[(j)],cont[(j+1)],CV_RGB(255,0,0),2);
}
line(img,cont[(5)],cont[(0)],CV_RGB(255,0,0),2);
imshow("myWindow", img);
}
}
What I would like to obtain is a vector that contains the coordinates of all the points of the contour and ultimately a bianary matrix the size of my image that contains 0 if the pixel is not in the contour, else 1.
Thanks for your help.

Answer 1

Make single element vector< vector< Point> > and then use drawContours with CV_FILLED. Then you will have binary matrix you wanted.
I currently don't have IDE but code will be like following
vector< vector< Point> > contours;
contours.push_back(cont);//your cont
Mat output(img.rows,img.cols,CV_8UC1);//your img
drawContours(output, contours, 0, Scalar(1), CV_FILLED);//now you have binary image