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Python OpenCV – cv2.polylines() method

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  • Difficulty Level : Basic
  • Last Updated : 15 Jun, 2022

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. 

ncontours: 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:

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()


Output:

  cv2.polylines()


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