Contours, hierarchy cv2 findcontours thresh cv2 retr_tree cv2 chain_approx_simple

1. What is hierarchy in cv2 contours?
2. What is cv2 findContours?
3. What does findContours return?
4. What is the output of cv2 findContours?

What is hierarchy in cv2 contours?

This way, contours in an image has some relationship to each other. And we can specify how one contour is connected to each other, like, is it child of some other contour, or is it a parent etc. Representation of this relationship is called the Hierarchy.

What is cv2 findContours?

OpenCV has findContour() function that helps in extracting the contours from the image. It works best on binary images, so we should first apply thresholding techniques, Sobel edges, etc. Below is the code for finding contours – import cv2. import numpy as np.

What does findContours return?

Since OpenCV 3.2, findContours() no longer modifies the source image but returns a modified image as the first of three return parameters. In OpenCV, finding contours is like finding white object from black background. So remember, object to be found should be white and background should be black.

What is the output of cv2 findContours?

cv2. drawContours(image,contours,-1,(255,0,0),2) # Drawing the detected contours on the image. It takes 5 values. Its first argument is source image, the second argument is the contours which should be passed as a Python list, the third argument is the index of contours (useful when drawing the individual contour.