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Python OpenCV – namedWindow() Function

  • Last Updated : 17 Oct, 2021

Python OpenCV namedWindow() method is used to create a window with a suitable name and size to display images and videos on the screen. The image by default is displayed in its original size, so we may need to resize the image for it to fit our screen.

Created windows are referred by their names and can also be used as a placeholder. The function does nothing If a window exists with the same name. 

Syntax: cv2.namedWindow(window_name, flag)

Parameters:

  • window_name: Name of the window that will display image/video
  • flag:  Represents if window size is automatically set or adjustable.

Some of the flag values are:

  • WINDOW_NORMAL – Allows to manually change window size
  • WINDOW_AUTOSIZE(Default) – Automatically sets the window size
  • WINDOW_FULLSCREEN – Changes the window size to fullscreen

Return Value: It doesn’t return anything

Image used for all the below examples:

Example 1: Working of namedWindow() method with automatically sets the window size

Python3




# Python program to explain cv2.namedWindow() method
  
# Importing OpenCV
import cv2
  
# Path to image in local directory
path = 'C:/Users/art/OneDrive/Desktop/geeks.png'
  
# Using cv2.imread() to read an image in default mode
image = cv2.imread(path)
  
# Using namedWindow()
# A window with 'Display' name is created
# with WINDOW_AUTOSIZE, window size is set automatically
cv2.namedWindow("Display", cv.WINDOW_AUTOSIZE)
  
# using cv2.imshow() to display the image
cv2.imshow('Display', image)
  
# Waiting 0ms for user to press any key
cv2.waitKey(0)
  
# Using cv2.destroyAllWindows() to destroy
# all created windows open on screen
cv2.destroyAllWindows()

Output:

Explanation

  • In this code, in order to use namedWindow function OpenCV python library is imported. 
  • Then by using cv2.imread, a file from a particular location(path) is loaded into ‘image’ variable in default mode. 
  • Now to create a window with ‘Display’ name and automatic size for image namedWindow is used. 
  • By using cv2.imshow, the custom window is displayed on the screen. After waiting for 0ms user can destroy all windows by pressing any key from the keyboard. 

Example 2: Manually change the window size 

Python3




# Python Program to explain namedWindow() method
  
# Importing OpenCV
import cv2
  
# Path to image in local directory
path = 'C:/Users/art/OneDrive/Desktop/geeks.png'
  
# Using cv2.imread() to read an image in grayscale mode
image = cv2.imread(path, 0)
  
# Using namedWindow()
# A window with 'Display_Image' name is created
# with WINDOW_NORMAL allowing us to have random size
cv2.namedWindow("Display_Image", cv.WINDOW_NORMAL)
  
# Using cv2.imshow() to display the image
cv2.imshow('Display_Image', image)
  
# Waiting 0ms for user to press any key
cv2.waitKey(0)
  
# Using cv2.destroyAllWindows() to destroy
# all created windows open on screen
cv2.destroyAllWindows()

Output:

Note: When a user randomly changes size, the window size is changed dimensions of the image remain unchanged.


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