timing_test.py

import cv2
import time
import numpy as np


IMG_SIZE = (250, 250)
NUM_ITERS = 500


def compare_tobytes_runtimes(img1, name1, img2, name2):
    t0 = time.perf_counter()
    for _ in range(NUM_ITERS):
        img1.tobytes()
    img1_t = time.perf_counter() - t0

    t0 = time.perf_counter()
    for _ in range(NUM_ITERS):
        img2.tobytes()
    img2_t = time.perf_counter() - t0

    print(f"Ratio of {name1}:{name2} = {(img1_t / img2_t):0.5f}")

if __name__ == "__main__":
        
    # Random image
    img_rand = np.random.randint(0, 256, IMG_SIZE, dtype=np.uint8)

    # Save it, turning it into a "real" image and making this script self sufficient.
    cv2.imwrite("real_image.png", img_rand)

    # Real image
    img_real = cv2.imread("real_image.png")
    img_real = img_real[:, :, 0]

    compare_tobytes_runtimes(img_real, "Real", img_rand, "Random")

    #
    # Why the near 100x difference?
    #

Output:

Ratio of Real:Random = 94.40609

Solution: https://gist.github.com/SarvagyaVaish/0e6b589e70a72e771076dd126cce1def