4. ImageOps pad

See: https://pillow.readthedocs.io/en/stable/reference/ImageOps.html#PIL.ImageOps.pad

4.1. Pad

Use the ImageOps.pad(image, size, method=Resampling.BICUBIC, color=None, centering=(0.5, 0.5)) method to return an image that has been resized to fill the size, keep the aspect ratio, with padding added as needed.
ImageOps.pad(image, size, method=Resampling.BICUBIC, color=None, centering=(0.5, 0.5))
image - The image to resize and crop.
size - The requested output size in pixels, given as a (width, height) tuple.
method - Resampling method to use. Default is PIL.Image.BICUBIC.
color - The background color of the padded image.
**centering**=(0.5, 0.5) will keep the image centered.
**centering**=(0, 0) will keep the image aligned to the top left.
**centering**=(1, 1) will keep the image aligned to the bottom right.
from PIL import Image, ImageOps

with Image.open("test_images/shapes.png") as im:
    im1 = ImageOps.pad(im, size=(200, 256), color="yellow", centering=(0.5, 0.5))
    im1.save("imageOps/pad.png")
../_images/compare_pad.png