python - How does cv2.findContours() edit the image?

Question

I have two questions.

1. I am working with openCv and python and I am trying to have an image's contours. I am succesfull at that but when I try to se what is the difference between when I use cv2.drawContorus() functions and directly edit image with cv2.findContours() without sending a copy of original image as the source parameter. I have tried on some images but I couldnt see anything even happenning.

2. I am trying to get the contours of a square I created with paint square tool. But when I try with cv2.CHAIN_APPROX_SIMPLE method, it gives me coordinates of 6 points which none of the combinations from them is suitable for my square. Why does it do like that?

Can someone explain?

Here is my code for both problems:

import cv2
import numpy as np

image = cv2.imread(r"C:UsersfazilDesktop12.png")
gray = cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
gray = cv2.Canny(gray,75,200)
gray = cv2.threshold(gray,127,255,cv2.THRESH_BINARY_INV)[1]
cv2.imshow("s",gray)
contours, hiearchy = cv2.findContours(gray,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
print(contours[1])
cv2.drawContours(image,contours,1,(45,67,89),5)
cv2.imshow("k",gray)
cv2.imshow("j",image)
cv2.waitKey(0)
cv2.destroyAllWindows()

question from:https://stackoverflow.com/questions/65907961/how-does-cv2-findcontours-edit-the-image

Answer 1

Waitting for answers