opencv find perimeter of a connected component

Question

I\'m using opencv 2.4.13

I\'m trying to find the perimeter of a connected component, I was thinking of using ConnectedComponentWithStats but it doesn\'t return the perim

Answer 1

Adding to @Miki's answer, This is a faster way to find the perimeter of the connected component

//getting the connected components with statistics
cv::Mat1i labels, stats;
cv::Mat centroids;

int lab = connectedComponentsWithStats(img, labels, stats, centroids);

for (int i = 1; i < lab; ++i)
{
    //Rectangle around the connected component
    cv::Rect rect(stats(i, 0), stats(i, 1), stats(i, 2), stats(i, 3));

    // Get the mask for the i-th contour
    Mat1b mask_i = labels(rect) == i;

    // Compute the contour
    vector> contours;     
    findContours(mask_i, contours, RETR_EXTERNAL, CHAIN_APPROX_NONE);

    if(contours.size() <= 0)
         continue;        

    //Finding the perimeter
    double perimeter = contours[0].size();
    //you can use this as well for measuring perimeter
    //double perimeter = arcLength(contours[0], true);

}