PIL Image stacking

stack.py

import numpy as np
from PIL import Image

def vstack(images):
    if len(images) == 0:
        raise ValueError("Need 0 or more images")

    if isinstance(images[0], np.ndarray):
        images = [Image.fromarray(img) for img in images]
    width = max([img.size[0] for img in images])
    height = sum([img.size[1] for img in images])
    stacked = Image.new(images[0].mode, (width, height))

    y_pos = 0
    for img in images:
        stacked.paste(img, (0, y_pos))
        y_pos += img.size[1]
    return stacked


def hstack(images):
    if len(images) == 0:
        raise ValueError("Need 0 or more images")

    if isinstance(images[0], np.ndarray):
        images = [Image.fromarray(img) for img in images]
    width = sum([img.size[0] for img in images])
    height = max([img.size[1] for img in images])
    stacked = Image.new(images[0].mode, (width, height))

    x_pos = 0
    for img in images:
        stacked.paste(img, (x_pos, 0))
        x_pos += img.size[0]
    return stacked

thanks for the snippet
import missing:
import numpy as np