How increase an image to a specific size by adding white transparent pixels in python (preferably using opencv)

Question

for example: original image's dimesion = 1080x720x4(4 as in blue, green, red and alpha channel) required dimension = 1920x1080x4 I want White transparent pixels (255,255,255,0) to be added in the border until it reaches the required dimension.

Maybe there is numpy function to help with this?

Answer 1

One way using Python/OpenCV is to use copyMakeBorder as suggested by @ Quang Hoang.

Input (100x116):

import cv2

# read image
img = cv2.imread("A.png", cv2.IMREAD_UNCHANGED)

img2 = cv2.copyMakeBorder(img, 50,50,50,50, borderType=cv2.BORDER_CONSTANT, value=(255,255,255,0))

cv2.imwrite("A_border.png", img2)

cv2.imshow("img2", img2)
cv2.waitKey(0)

Result (200x2016):