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A bug causes crash when class inherit from cv2.KeyPoint

asked 2019-07-15 02:39:12 -0500

Look this code:

import numpy as np
import cv2
class T(cv2.KeyPoint):
    def __init__(self, pt):
        super().__init__() = pt
def calculate_corners(A):
    A_gray = cv2.cvtColor(A, cv2.COLOR_BGR2GRAY)
    pa = cv2.goodFeaturesToTrack(A_gray, maxCorners=100, qualityLevel=0.01, minDistance=15)
    pa = np.squeeze(pa)
    kpa = []
    for coor in pa:
    return kpa

cap = cv2.VideoCapture("E:\\video\\test.mp4")
while True:
    frame =[1]
    if frame is None:
    kpa = calculate_corners(frame)
    frame_corner = cv2.drawKeypoints(frame, kpa, outImage=None, color=(255, 0, 125))
    cv2.imshow('frame_corner', frame_corner)

This code will crash in my system(Windows10, python3.7.3, opencv4.1.0)

After test, I'm sure this is caused by class T. I guess that class T dose not inherit release moudle of cv2.KeyPoint, so it cause memory leak. It's just my conjecture. And I didn't know how to fix it. Could anyone give me some advice? Thanks a lot!

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error msg is missing, please add that.

please also try to explain, WHY you wanted to do it like this, and why you think you need OOP / inheritance here (which is mostly a terrible design idea)

please also remember, that opencv is mainly a c++ library, not a pure python one.

berak gravatar imageberak ( 2019-07-15 03:48:36 -0500 )edit

@berak Yes, I recognize it's a terrible design idea. I would like to post the error message if I got it. But the program crash without any error message. Finally I replaced T(tuple(coor)) with cv2.KeyPoint(x=coor[0], y=coor[1], _size=0). At first, I just want to use the drawKeypoints function, but I don't how to transform points from matrix into KeyPoints, so I thought out this terrible idea. I'm sorry about that.

0811张庆昊 gravatar image0811张庆昊 ( 2019-07-15 21:26:15 -0500 )edit

I replaced T(tuple(coor)) with cv2.KeyPoint(x=coor[0],...

yea, you found the solution already, good ! ;)

so, you only need keypoints, to use the drawKeyPoints() function ?

berak gravatar imageberak ( 2019-07-16 00:23:30 -0500 )edit

@berak Yes! Do you have any better or more elegant solution?

0811张庆昊 gravatar image0811张庆昊 ( 2019-07-16 02:10:35 -0500 )edit

gftt returns a list of points, you could just iterate it and draw a circle() per point on your own (homework, hehe ;)

then, again donn't worry too much about it now. gfft points are usually more used for (LK-) tracking, not so much for keypoint/decscriptor/matching, you'll probably use ORB, AKAZE, SURF or similar for this purpose instead later..

berak gravatar imageberak ( 2019-07-16 02:17:39 -0500 )edit

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answered 2019-07-16 05:50:28 -0500

@berak Yes, of course I can implement it in this way. In fact, I have implemented it in other project. But I think that use it in different projects is a little cumbersome. So I want use the API in cv2 straightly. Exactly, I use gftt for LK-tracking to implement a video stablization algorithm, so gftt is fit for me. Anyway, thanks for your reply! ^_^

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Asked: 2019-07-15 02:39:12 -0500

Seen: 265 times

Last updated: Jul 15 '19