In this article, we are going to see how to draw the minimum enclosing circle covering the object using OpenCV Python. For that, we will be using the concepts of Contours.
Let’s start with the code :
Import-Module and read images
In this step, we will import the OpenCV library and then read the image with its help.
Python3
import cv2 # To read image img = cv2.imread("cloud.png", cv2.IMREAD_COLOR) cv2.imshow("Image", img) cv2.waitKey(0) cv2.destroyAllWindows() |
Output:
Convert image to grayscale
To get a clear image we need to convert it into grayscale.
Python3
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) ret, thresh = cv2.threshold(gray, 127, 255, 0) |
Find the contours in the image
Contours can be extracted by using cv2.findContours() function. We can select a contour cnt or loop over the all contour
Python3
# finding the contours contours, _ = cv2.findContours(thresh, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) # take the first contour count = contours[0] |
Printing moments
Let’s print the moments for the contours we get.
Python3
M = cv2.moments(count) print(M) |
Output:
{'m00': 4781.5, 'm10': 554065.5, 'm01': 684678.6666666666, 'm20': 66858944.916666664,
'm11': 78978179.04166666, 'm02': 99446416.41666666, 'm30': 8363188151.05, 'm21': 9486949067.266666,
'm12': 11421819195.433332, 'm03': 14643992682.300001, 'mu20': 2655540.4849506766, 'mu11': -360277.0465901643,
'mu02': 1405032.6273862273, 'mu30': 347729.0371904373, 'mu21': -3306939.5028494596, 'mu12': 1453113.8002238572,
'mu03': 1551705.8647060394, 'nu20': 0.11615144219852615, 'nu11': -0.015758260433092374,
'nu02': 0.061455122575518134, 'nu30': 0.00021995333829451466, 'nu21': -0.002091779245894235,
'nu12': 0.0009191560010733997, 'nu03': 0.0009815196560831125}
Drawing and Displaying Circle Boundary
In this step, we will see how the circle will cover the cloud in the image using cv2.minEnclosingCircle().
Syntax : (x,y),radius = cv2.minEnclosingCircle(cnt)
where “cnt” are the contour points.
Python3
(x_axis,y_axis),radius = cv2.minEnclosingCircle(count) center = (int(x_axis),int(y_axis)) radius = int(radius) cv2.circle(img,center,radius,(0,255,0),2) cv2.imshow("Image",img) cv2.waitKey(0) cv2.destroyAllWindows() |
Output:
