Howto Extract PNG from binary file @ 0x80?

[flamesrock]

omg, it works!! thankyou!!!!!
and thankyou again, Frederick for the original code!

I've discovered a weird thing when changing header = infile.read(8) to
header = infile.read(4):
For some reason, the extracted png image is the exact same size as the
savegame archive (10.1 megs.) When reading 8bytes, its closer to
~200kb. Any clue as to why that is?

-thanks

#import struct
#
#def pngcopy(infile, outfile):
#
#   # copy header
#   header = infile.read(8)
#   if header != "\211PNG\r\n\032\n":
#       raise IOError("not a valid PNG file")
#   outfile.write(header)
#
#   # copy chunks, until IEND
#   while 1:
#       chunk = infile.read(8)
#       size, cid = struct.unpack("!l4s", chunk)
#       outfile.write(chunk)
#       outfile.write(infile.read(size))
#       outfile.write(infile.read(4)) # checksum
#       if cid == "IEND":
#           break
#
#
#infile = open("mysimcityfile.sc4", "rb")
#infile.seek(96)
###print (infile.read(4))
#outfile = open("myimage.png", "wb")
#pngcopy(infile, outfile)
#outfile.close()
#infile.close()

(http://simcitysphere.com/peachville.sc4)