split.py

from PIL import Image

WIDTH = 25
HEIGHT = 25
PAD_HEIGHT = 3
PAD_WIDTH = 3

source = Image.open("grid.png")
width, height = source.size

left = 0
right = left + WIDTH

x = 1
y = 1

while left <= width:
    top = 0
    bottom = top + HEIGHT

    while top <= height:
        sprite = source.crop((left, top, right, bottom))
        sprite.save("{:02}x{:02}.png".format(x, y))

        top += HEIGHT + PAD_HEIGHT
        bottom = top + HEIGHT
        y += 1

    left += WIDTH + PAD_WIDTH
    right = left + WIDTH
    x += 1