高斯噪声没有覆盖主要图像-Python

Question

I'm trying to add Gaussian noise to an image("pepper.jpg"). It works, as shown in the result ("noisy pepper.png"); but the noise is not covering the "peppers" and it is around it. Is there something I'm missing in applying noise? Any advice would be appreciated.

import cv2
import numpy as np

img = cv2.imread("pepper.jpg",0)
row, col = img.shape
mean = 0
var = 0.3
sigma = var ** 0.5
gauss = np.random.normal(mean, sigma, (row, col))
gauss = gauss.reshape(row, col)
noisyp = gauss + img
noisyp = noisyp.astype('uint8')
cv2.imwrite('noisy pepper.png', noisyp)

Regards, Behrouz

Answer 1

Your convertion to uint8 isn't complex. Here is what you are looking for:

import cv2
import numpy as np


def convert_to_uint8(image_in):
    temp_image = np.float64(np.copy(image_in))
    cv2.normalize(temp_image, temp_image, 0, 255, cv2.NORM_MINMAX, dtype=-1)

    return temp_image.astype(np.uint8)


img = cv2.imread("pepper.jpg", 0)
row, col = img.shape
mean = 0
var = 0.3
sigma = var ** 0.5
gauss = np.random.normal(mean, sigma, (row, col))
gauss = gauss.reshape(row, col)
noisy_pepper = gauss + img

cv2.imwrite('noisy pepper.png', convert_to_uint8(noisy_pepper))

Of course witch such sigma you ain't gonna see the noise. Please take look at this one (sigma will be around 14):

..
var = 200
sigma = var ** 0.5
..