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Python OpenCV | cv2.circle() method

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  • Difficulty Level : Easy
  • Last Updated : 07 Jun, 2022
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OpenCV-Python is a library of Python bindings designed to solve computer vision problems. cv2.circle() method is used to draw a circle on any image. The syntax of cv2.circle() method is:

Syntax: 

cv2.circle(image, center_coordinates, radius, color, thickness)

Parameters: 

  • image: It is the image on which the circle is to be drawn. 
  • center_coordinates: It is the center coordinates of the circle. The coordinates are represented as tuples of two values i.e. (X coordinate value, Y coordinate value). 
  • radius: It is the radius of the circle. 
  • color: It is the color of the borderline of a circle to be drawn. For BGR, we pass a tuple. eg: (255, 0, 0) for blue color. 
  • thickness: It is the thickness of the circle border line in px. Thickness of -1 px will fill the circle shape by the specified color.

Return Value: It returns an image. 

The steps to create a circle on an image are:

  1. Read the image using imread() function.
  2. Pass this image to the cv2.circle() method along with other parameters such as center_coordinates, radius, color and thickness.
  3. Display the image using cv2.imshow() method.

Implementation:

Image used for all the below examples:  

Example #1:

Python3




# Python program to explain cv2.circle() method
   
# importing cv2
import cv2
   
# path
path = r'C:\Users\Rajnish\Desktop\geeksforgeeks\geeks.png'
   
# Reading an image in default mode
image = cv2.imread(path)
   
# Window name in which image is displayed
window_name = 'Image'
  
# Center coordinates
center_coordinates = (120, 50)
 
# Radius of circle
radius = 20
  
# Blue color in BGR
color = (255, 0, 0)
  
# Line thickness of 2 px
thickness = 2
  
# Using cv2.circle() method
# Draw a circle with blue line borders of thickness of 2 px
image = cv2.circle(image, center_coordinates, radius, color, thickness)
  
# Displaying the image
cv2.imshow(window_name, image)


Output: 

 Example #2: Using thickness of -1 px to fill the circle with red color. 

Python3




# Python program to explain cv2.circle() method
   
# importing cv2
import cv2
   
# path
path = r'C:\Users\Rajnish\Desktop\geeksforgeeks\geeks.png'
   
# Reading an image in default mode
image = cv2.imread(path)
   
# Window name in which image is displayed
window_name = 'Image'
  
# Center coordinates
center_coordinates = (120, 100)
 
# Radius of circle
radius = 30
  
# Red color in BGR
color = (0, 0, 255)
  
# Line thickness of -1 px
thickness = -1
  
# Using cv2.circle() method
# Draw a circle of red color of thickness -1 px
image = cv2.circle(image, center_coordinates, radius, color, thickness)
  
# Displaying the image
cv2.imshow(window_name, image)


Output: 

 Example # 3: To display a circle on a black screen created using NumPy library.

Python3




import cv2
import numpy as np
    
 
# Reading an image in default mode
Img = np.zeros((512, 512, 3), np.uint8)
    
# Window name in which image is displayed
window_name = 'Image'
   
# Center coordinates
center_coordinates = (220, 150)
  
# Radius of circle
radius = 100
   
# Red color in BGR
color = (255, 133, 233)
   
# Line thickness of -1 px
thickness = -1
   
# Using cv2.circle() method
# Draw a circle of red color of thickness -1 px
image = cv2.circle(Img, center_coordinates, radius, color, thickness)
   
# Displaying the image
cv2.imshow(window_name, image)
cv2.waitKey(0)
cv2.destroyAllWindows()


Output:

Circle on Black background 


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