opencv remove png background

#To set transparent background to white (or any other colour):

import cv2
#load image with alpha channel.  use IMREAD_UNCHANGED to ensure loading of alpha channel
image = cv2.imread('your image', cv2.IMREAD_UNCHANGED)    

#make mask of where the transparent bits are
trans_mask = image[:,:,3] == 0

#replace areas of transparency with white and not transparent
image[trans_mask] = [255, 255, 255, 255]

#new image without alpha channel...
new_img = cv2.cvtColor(image, cv2.COLOR_BGRA2BGR)

#courtesy of @user1269942 https://stackoverflow.com/questions/53732747/set-white-background-for-a-png-instead-of-transparency-with-opencv