from PIL import Image

size = 16

im = Image.open("cards-001.png")
w = 0
h = 0

while h + size < im.size[1]:
  w = 0
  while w + size < im.size[0]:
    im.crop((w, h, w+size, h+size)).save('cards-001-%s-%s.png' % (h, w))