Calculate the area of an object with OpenCV

Question

I need to calculate the area of a blob/an object in a grayscale picture (loading it as Mat, not as IplImage) using OpenCV. I thought it would be a good idea to get

Answer 1

contours is actually defined as

vector<vector<Point> > contours;

And now I think it's clear how to access its points.

The contour area is calculated by a function nicely called contourArea():

for (unsigned int i = 0;  i < contours.size();  i++)
{
     std::cout << "# of contour points: " << contours[i].size() << std::endl;

     for (unsigned int j=0;  j<contours[i].size();  j++)
     {
         std::cout << "Point(x,y)=" << contours[i][j] << std::endl;
     }

     std::cout << " Area: " << contourArea(contours[i]) << std::endl;
}