Python OpenCV – imdecode() Function

Python cv2.imdecode() function is used to read image data from a memory cache and convert it into image format. This is generally used for loading the image efficiently from the internet. 

Syntax: cv2.imdecode(buf,flags)

Parameters:

• buf – It is the image data received  in bytes
• flags – It specifies the way in which image should be read. It’s default value is cv2.IMREAD_COLOR

Return: Image array

Note: If buf given is not image data then NULL will be returned.

Example 1:

Python3

#import modules
import numpy as np
import urllib.request
import cv2

# read the image url
url = 'https://media.geeksforgeeks.org/wp-content/uploads/20211003151646/geeks14.png'


with urllib.request.urlopen(url) as resp:

    # read image as an numpy array
    image = np.asarray(bytearray(resp.read()), dtype="uint8")

    # use imdecode function
    image = cv2.imdecode(image, cv2.IMREAD_COLOR)

    # display image
    cv2.imwrite("result.jpg", image)

Output:

Example 2: If grayscale is required, then 0 can be used as flag.

Python3

# import necessary modules
import numpy as np
import urllib.request
import cv2

# read image url
url = 'https://media.geeksforgeeks.org/wp-content/uploads/20211003151646/geeks14.png'

with urllib.request.urlopen(url) as resp:

    # convert to numpy array
    image = np.asarray(bytearray(resp.read()), dtype="uint8")

    # 0 is used for grayscale image
    image = cv2.imdecode(image, 0)

    # display image
    cv2.imwrite("result.jpg", image)

Output:

Example 3: Reading image from a file

Input Image:

Python3

# import necessayr modules
import numpy as np
import urllib.request
import cv2

# read th image
with open("image.jpg", "rb") as image:

    f = image.read()

    # convert to numpy array
    image = np.asarray(bytearray(f))

    # RGB to Grayscale
    image = cv2.imdecode(image, 0)

    # display image
    cv2.imshow("output", image)

Output: