import cv2
import numpy as np

image_original = cv2.imread('cat.jpg')

# convert to HSV color space
hsv_image = cv2.cvtColor(image_original, cv2.COLOR_BGR2HSV)

# define range of background color in HSV
lower_green = (45, 125, 125)
upper_green = (75, 255, 255)

mask = cv2.inRange(hsv_image, lower_green, upper_green)

image_original_copy = image_original.copy()
image_original[np.where(mask == 255)] = [0, 0, 0]

np.hstack((image_original_copy, image_original))
cv2.imwrite('cat2.jpg', image_original)