from PIL import Image
import sys

i, o = sys.argv[1:]

im = Image.open(i)
# In pass.hust.edu.cn verification code, the second frame is COMPLETE!
# let's get the second frame.
im.seek(im.tell()+1)
im.save(o)

im = Image.open(o)
# To white-black
im = im.convert('L')
im = im.point(lambda x: 0 if x<254 else 255, '1')
# Try to crop
w, h = im.size
if w == 90 and h == 58:
    im = im.crop((0, 18, w, 39))
else:
    print('WARNING: Expected image w=90, h=58, Got image w={}, h={}.'.format(w, h))
# Save for OCR
im.save(o)