nimpy

import numpy as np
def calculate_psnr(img1, img2, max_value=255):
    """"Calculating peak signal-to-noise ratio (PSNR) between two images."""
    mse = np.mean((np.array(img1, dtype=np.float32) - np.array(img2, dtype=np.float32)) ** 2)
    if mse == 0:
        return 100
    return 20 * np.log10(max_value / (np.sqrt(mse)))

nimpy

import numpy as np
def add_gaussian_noise(image, mean=0, sigma=20):
    """Add Gaussian noise to an image of type np.uint8."""
    gaussian_noise = np.random.normal(mean, sigma, image.shape)
    gaussian_noise = gaussian_noise.reshape(image.shape)
    noisy_image = image + gaussian_noise
    noisy_image = np.clip(noisy_image, 0, 255)
    noisy_image = noisy_image.astype(np.uint8)
    return noisy_image

nimpy

import numpy as np
def calculate_ssd(img1, img2):
    """Computing the sum of squared differences (SSD) between two images."""
    if img1.shape != img2.shape:
        print("Images don't have the same shape.")
        return
    return np.sum((np.array(img1, dtype=np.float32) - np.array(img2, dtype=np.float32))**2)