parallel PNG checker

pngchecker.py (text/x-python), 1.60 KB, created by Tobias Klausmann (RETIRED) on 2013-04-20 13:08:31 UTC

#!/usr/bin/python3 -tt
# Copyright 2013 T. Klausmann.
# Licensed under the GPL-2.
"""
Check PNG files supplied on stdin for "IDAT: invalid distance too far back"
errors.
"""


import multiprocessing
import os
import subprocess
import sys
import time

JOBS = 8 # Number of jobs to run in parallel.

def test_one_file(filename):
    """
    Test one file by using ImageMagick's convert tool

    Tries to convert the file to /tmp/garbage.png. If the return value is not
    zero _and_ the string "IDAT: invalid distance too far back" is in convert's
    stdout, return the filename. Otherwise, return None. Does not clean up
    /tmp/garbage.png.
    """
    cmd = "convert '%s' /tmp/garbage.png" % (filename)
    (retval, output) = subprocess.getstatusoutput(cmd)
    with open("/tmp/pngfixer/checker.%i.log" % os.getpid(), "w") as logfd:
        logfd.write(output)
    if retval != 0 and "IDAT: invalid distance too far back" in output:
        return  filename

def main():
    """Main program."""
    pool = multiprocessing.Pool(processes=JOBS)
    # If your filesystem contains files with \n in their names, you need to seek
    # help.
    inputfiles = sys.stdin.read().split("\n")
    start = time.time()
    result = pool.map(test_one_file, inputfiles)
    end = time.time()
    timedelta = end-start
    amount = len(inputfiles)
    print("Checked %s files in %.2f seconds, %.2f files/s." % 
          (amount, timedelta, amount/timedelta))
    # Drop instances of None
    result = [ x for x in result if x ]

    print("%s files need fixing." %(len(result)))
    print("\n".join(result))

if __name__ == "__main__":
    main()