Life2Coding
Loading Image in Python using OpenCV

This post will be helpful in learning OpenCV using Python programming. Here I will show how to implement OpenCV functions and apply it in various aspects using some examples. Then the output will be shown with some comparisons as well.

Requirements:

First, you need to setup your Python Environment with OpenCV. You can easily do it by following Life2Coding’s tutorial on YouTube: Linking OpenCV 3 with Python 3

Goals:

In this tutorial, I will show you how to load an image in python and display it in a window using OpenCV library.

Documentation:

Python: cv2.imread(filename[, flags]) → retval

Loads an image from a file.

Parameters:

  • filename– Name of file to be loaded.
  • flags – Flags specifying the color type of a loaded image:
    1. cv2.IMREAD_COLOR : Loads a color image. Any transparency of image will be neglected. It is the default flag.
    2. cv2.IMREAD_GRAYSCALE : Loads image in grayscale mode
    3. cv2.IMREAD_UNCHANGED : Loads image as such including alpha channel

Note: Instead of these three flags, you can simply pass integers 1, 0 or -1 respectively

Python: cv2.imshow(winname, mat) → None

Displays an image in the specified window.

Parameters:

  • winname – Name of the window.
  • image – Image to be shown.

The function imshow displays an image in the specified window. If the window was created with the CV_WINDOW_AUTOSIZE flag, the image is shown with its original size. Otherwise, the image is scaled to fit the window.

Steps:

  • Load Image using cv2.imread()
  • Create window using cv2.namedWindow()
  • Display Image using cv2.imshow()
  • Wait for keyboard button press using cv2.waitKey()
  • Exit window and destroy all windows using cv2.destroyAllWindows()

Example Code:

import cv2
import numpy as np
import sys

def main():
    imgpath = "Hanif.jpg"

    img = cv2.imread(imgpath,cv2.IMREAD_COLOR) # load image from file
    cv2.namedWindow('Hanif',cv2.WINDOW_AUTOSIZE) # for resizing use 'cv2.WINDOW_NORMAL'

    cv2.imshow('Hanif', img) # display the image
    cv2.waitKey(0) # wait for keyboard interrupt
    cv2.destroyAllWindows() # destroy all the windows

if __name__ == "__main__":
    main()

Output:

Load-Image Loading Image in Python using OpenCV

life2coding_icon [] Loading Image in Python using OpenCV

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