cv2.error: OpenCV(4.1.1) C:\projects\opencv-python\opencv\modules\imgproc\src\shapedescr.cpp:274: error: (-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S) in function 'cv::contourArea'

[saikumarvaddepally15]

[nguyenthanhluan98]

In opencv 4.1.1, cv2.findContours return 2 values
let try it
contours,hierarchy = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
https://stackoverflow.com/questions/54273763/assertion-error-215-npoints-0-and-error-while-extracting-letters-from-capt

[snehitvaddi]

@saikumarnani0304 Fasing same issue. After adding hierarchy it is giving error like :
Expected Ptr<cv::UMat> for argument '%s'.
My code looks like this!!

[zoldaten]

that is not an opencv issue it seems to be that problems with camera. no access to it. try different camera or try to change videoinput from 0 to 1.