When using findContours to identify blobs, is there a way to ignore any contours present within another contour. I only need to count the number of contours that are the outermost using contours.size();
I looked into this and found the RETR_EXTERNAL parameter instead of the RETR_LIST, is this enough? Or do I have to do anything with the hierarchy Mat object (third parameter)?
I think that you and sammy have already found the answer. This is what the documentation says:
RETR_EXTERNAL retrieves only the extreme outer contours.
For hierarchy it states that:
Optional output vector, containing information about the image topology. It has as many elements as the number of contours. For each i-th contour contours[i] , the elements hierarchy[i] [0] , hiearchy[i][1] ,hiearchy[i][2] , and hiearchy[i][3] are set to 0-based indices in contours of the next and previous contours at the same hierarchical level, the first child contour and the parent contour, respectively.
So in case of RETR_EXTERNAL you can use hierarchy[i][0] and hierarchy[i][1] for "neighbouring" contours at the top level but hierarchy[i][2] and hierarchy[i][3] will always be -1.
You can see this link for better understanding the flags of the function
Asked: 2012-08-02 10:06:33 -0600
Seen: 7,157 times
Last updated: Jan 05 '16
Using RETR_EXTERNAL gave you bad results? What have you tried so far?
Gave somewhat of a better answer (RETR_EXTERNAL). Was wondering whether it could be more refined...