Add padding to images to get them into the same shape

Question

l have a set of images of different sizes (45,50,3), (69,34,3), (34,98,3). l want to add padding to these images as follows:

Take the max width and leng

Answer 1

Here is another way to do that in Python/OpenCV/Numpy. It uses numpy slicing to copy the input image into a new image of the desired output size and a given offset. Here I compute the offset to do center padding. I think this is easier to do using width, height, xoffset, yoffset, rather than how much to pad on each side.

Input:

import cv2
import numpy as np

# read image
img = cv2.imread('lena.jpg')
ht, wd, cc= img.shape

# create new image of desired size and color (blue) for padding
ww = 300
hh = 300
color = (255,0,0)
result = np.full((hh,ww,cc), color, dtype=np.uint8)

# compute center offset
xx = (ww - wd) // 2
yy = (hh - ht) // 2

# copy img image into center of result image
result[yy:yy+ht, xx:xx+wd] = img

# view result
cv2.imshow("result", result)
cv2.waitKey(0)
cv2.destroyAllWindows()

# save result
cv2.imwrite("lena_centered.jpg", result)