Reading images in OpenCV

The following example, argparse_load_image.py, shows you how to load an image:

# Import the required packages
import argparse
import cv2

# We first create the ArgumentParser object 
# The created object 'parser' will have the necessary information
# to parse the command-line arguments into data types.
parser = argparse.ArgumentParser()

# We add 'path_image' argument using add_argument() including a help. The type of this argument is string (by default)
parser.add_argument("path_image", help="path to input image to be displayed")

# The information about program arguments is stored in 'parser'
# Then, it is used when the parser calls parse_args().
# ArgumentParser parses arguments through the parse_args() method:
args = parser.parse_args()

# We can now load the input image from disk:
image = cv2.imread(args.path_image)

# Parse the argument and store it in a dictionary:
args = vars(parser.parse_args())

# Now, we can also load the input image from disk using args:
image2 = cv2.imread(args["path_image"])

# Show the loaded image:
cv2.imshow("loaded image", image)
cv2.imshow("loaded image2", image2)

# Wait until a key is pressed:
cv2.waitKey(0)

# Destroy all windows:
cv2.destroyAllWindows()

In this example, the required argument is path_image, which contains the path of the image we want to load. The path of the image is a string. Therefore, no type should be included in the positional argument because it is a string by default. Both args.path_image and args["path_image"] will contain the path of the image (two different ways of getting the value from the parameter), so we will use them as the parameter of the cv2.imread() function.