Python OpenCV - cv2.polylines() method

Python OpenCV – cv2.polylines() method

Last Updated : 21 Apr, 2020

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

# 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:

# 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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