Opencv polylines function in python throws exception
The problem in my case was that numpy.array created int64-bit numbers by default. So I had to explicitly convert it to int32:
points = np.array([[910, 641], [206, 632], [696, 488], [458, 485]])# points.dtype => 'int64'cv2.polylines(img, np.int32([points]), 1, (255,255,255))(Looks like a bug in cv2 python binding, it should've verified dtype)
This function is not enough well documented and the error are also not very useful. In any case, cv2.polylines expects a list of points, just change your line to this:
import cv2import numpy as npimg = np.zeros((768, 1024, 3), dtype='uint8')points = np.array([[910, 641], [206, 632], [696, 488], [458, 485]])cv2.polylines(img, [points], 1, (255,255,255))winname = 'example'cv2.namedWindow(winname)cv2.imshow(winname, img)cv2.waitKey()cv2.destroyWindow(winname)The example above will print the following image (rescaled):
