from PIL import Image, ImageChops, ImageEnhance
import sys,json,os
for prefix in sys.argv[1:]:
 a=Image.open(prefix+'-before.png').convert('RGB'); b=Image.open(prefix+'-after.png').convert('RGB')
 assert a.size==b.size,(a.size,b.size)
 d=ImageChops.difference(a,b)
 d.point(lambda x:min(255,x*255)).save(prefix+'-diff0.png')
 channels=d.split(); m=ImageChops.lighter(ImageChops.lighter(channels[0],channels[1]),channels[2])
 m.point(lambda x:255 if x>8 else 0).save(prefix+'-diffT8.png')
 print(prefix,a.size,'changed pixel bbox',m.getbbox(),'zero-changed',sum(1 for p in m.getdata() if p),'threshold8-changed',sum(1 for p in m.getdata() if p>8))