OpenCV 3.1 drawContours '(-215) npoints > 0'

Question

I\'m trying to create a mask from a contour, but am getting a C++ error.

Using OS X Yosemite, Python 2.7.10, OpenCV 3.1.0.

def create_mask(img, cnt):
            


        

Answer 1

You might have commited mistake while finding the contours. Contour is the second value returned by findContours() function as the docs say

im2, contours, hierarchy = cv.findContours(thresh, cv.RETR_TREE, cv.CHAIN_APPROX_SIMPLE)

So the following code will not work

cnt = cv2.findContours(thresh, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)

This might solve your problem.