Python OpenCV - cv2.polylines() method

Last Updated : 28 Apr, 2025

OpenCV is the huge open-source library for computer vision, machine learning, and image processing and it now plays a major role in real-time operations which are very important in today’s systems. By using OpenCV one can process images and videos to identify objects, faces, or even the handwriting of a human. When it is combined with various libraries such as Numpy, Python is capable of processing the OpenCV array structure for analysis.

Note: For more information, refer to OpenCV Python Tutorial

cv2.polylines()

cv2.polylines() method is used to draw a polygon on any image.

Syntax: cv2.polylines(image, [pts], isClosed, color, thickness)

Parameters: image: It is the image on which circle is to be drawn.

pts: Array of polygonal curves.

npts: Array of polygon vertex counters.

contours: Number of curves.

isClosed: Flag indicating whether the drawn polylines are closed or not. If they are closed, the function draws a line from the last vertex of each curve to its first vertex.

color: It is the color of polyline to be drawn. For BGR, we pass a tuple.

thickness: It is thickness of the polyline edges.

Return Value: It returns an image.

Image used for all the below examples:

Example #1:

Python3

# Python program to explain 
# cv2.polylines() method 

import cv2
import numpy as np

# path
path = gfg.jpeg'

# Reading an image in default
# mode
image = cv2.imread(path)

# Window name in which image is
# displayed
window_name = 'Image'

# Polygon corner points coordinates
pts = np.array([[25, 70], [25, 160], 
                [110, 200], [200, 160], 
                [200, 70], [110, 20]],
               np.int32)

pts = pts.reshape((-1, 1, 2))

isClosed = True

# Blue color in BGR
color = (255, 0, 0)

# Line thickness of 2 px
thickness = 2

# Using cv2.polylines() method
# Draw a Blue polygon with 
# thickness of 1 px
image = cv2.polylines(image, [pts], 
                      isClosed, color, thickness)

# Displaying the image
while(1):
    
    cv2.imshow('image', image)
    if cv2.waitKey(20) & 0xFF == 27:
        break
        
cv2.destroyAllWindows()

Output:

cv2.polylines()

Example #2:

Python3

# Python program to explain 
# cv2.polylines() method

import cv2
import numpy as np

# path
path = r'gfg.jpeg'

# Reading an image in default 
# mode
image = cv2.imread(path)

# Window name in which image is 
# displayed
window_name = 'Image'

# Polygon corner points coordinates
pts = np.array([[25, 70], [25, 145],
                [75, 190], [150, 190],
                [200, 145], [200, 70], 
                [150, 25], [75, 25]],
               np.int32)

pts = pts.reshape((-1, 1, 2))

isClosed = True

# Green color in BGR
color = (0, 255, 0)

# Line thickness of 8 px
thickness = 8

# Using cv2.polylines() method
# Draw a Green polygon with 
# thickness of 1 px
image = cv2.polylines(image, [pts], 
                      isClosed, color, 
                      thickness)

# Displaying the image
while(1):
    
    cv2.imshow('image', image)
    if cv2.waitKey(20) & 0xFF == 27:
        
        break
cv2.destroyAllWindows()