
f = open('cat.bmp', "rb")
d = f.read()
print d[:16]
import struct
print struct.unpack("<ccihhi", d[:14])
print len(d)
print struct.unpack("<iiihhiiiiii", d[14:54])
print len(d)
d2 = d[:54] + (len(d)-54)*'\xff'
open("cat1.bmp", "wb").write(d2)
d2 = d[:54] + (len(d) - 54)*'\x00'
open("cat2.bmp", "wb").write(d2)