Blur a specific part of an image

Question

I have an image. Like this:

I detect a subject(which is a person in this case) & it masks the image like this:

I want the background of

Answer 1

You may use np.where() method to select the pixels where you want blurred values and then replace them as:

import cv2
import numpy as np

img = cv2.imread("/home/user/Downloads/lena.png")
blurred_img = cv2.GaussianBlur(img, (21, 21), 0)

mask = np.zeros((512, 512, 3), dtype=np.uint8)
mask = cv2.circle(mask, (258, 258), 100, np.array([255, 255, 255]), -1)

out = np.where(mask==np.array([255, 255, 255]), img, blurred_img)

cv2.imwrite("./out.png", out)

Answer 2

as ZdaR said:

import cv2
import numpy as np

img = cv2.imread("/home/user/Downloads/lena.png")
blurred_img = cv2.GaussianBlur(img, (21, 21), 0)

mask = np.zeros((512, 512, 3), dtype=np.uint8)
mask = cv2.circle(mask, (258, 258), 100, np.array([255, 255, 255]), -1)

out = np.where(mask==np.array([255, 255, 255]), img, blurred_img)

cv2.imwrite("./out.png", out)

this is good idea but I've got same error as penta:

@ZdaR I get TypeError: Scalar value for argument 'color' is not numeric

the simple solution is modifying color value when you create Circle:

mask = cv2.circle(mask, (258, 258), 100, (255, 255,255), -1)

just CHANGE np,array([255,255,255]) to (255,255,255).