image files renamer

image_renamer.py

#!/usr/bin/python
#
# renames a directory of files with their image extension
# currently works with only JPEG and PNG files
#
# 2014.02.25 darell tan
#

import os
import sys


def id_file(filename):
	"""Primitive (but cheap) method of identifying an image file."""

	f = open(filename, 'rb')
	sig = f.read(4)
	f.close()

	if sig[:2] == '\xff\xd8':
		return 'jpg'
	elif sig[1:4] == 'PNG':
		return 'png'

	return None


def main():
	d = sys.argv[1]
	assert os.path.isdir(d)

	for f in os.listdir(d):
		if f == '.' or f == '..':
			continue

		# form full path
		fp = os.path.join(d, f)

		# make sure it's a file
		if not os.path.isfile(fp):
			continue

		# does it already have an extension?
		if f[-4:-3] == '.':
			continue

		print(f)

		typ = id_file(fp)
		if typ and not f.endswith(typ):
			os.rename(fp, '%s.%s' % (fp, typ))

if __name__ == '__main__':
	main()