png资源提取器

png_hunter.py

#!/usr/bin/python
import os
import sys
import struct

ifp = sys.stdin
pngcount = 0
filename = ""

def findstart():
    pos = ifp.tell()
    while True:
        magic = ifp.read(8)
        pos = pos + len(magic)
        if not magic:
            return -1
        if magic == "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a":
            return pos-8
        pos = pos - len(magic) + 1
        ifp.seek(pos)
    return -1

def findend():
    pos = ifp.tell()
    while True:
        magic = ifp.read(8)
        pos = pos + len(magic)
        if not magic:
            return -1
        if magic[4:] == "IEND":
            chunk, = struct.unpack("I", magic[0:4])
            return pos - 8 + chunk
        pos = pos - len(magic) + 1
        ifp.seek(pos)
    return -1

def save(s, e):
    global pngcount
    ofp = open("%s_%d.png"%(filename, pngcount), "wb+")
    ifp.seek(s)
    ofp.write(ifp.read(e-s))
    ofp.close()
    pngcount = pngcount + 1
    return

def main():
    while True:
        s = findstart()
        if s < 0:
            break
        e = findend()
        if e < 0:
            break
        save(s, e)
        pass

if __name__ == "__main__":
    filename = os.path.basename(sys.argv[1])
    ifp = open(sys.argv[1], "rb")
    if not ifp:
        print "No such a file", sys.argv[1]
    else:
        main()