jpeg-eoi.py

#!/usr/bin/env python

from __future__ import absolute_import
from __future__ import unicode_literals
from __future__ import division
from __future__ import print_function

import sys
import os
import re
import argparse
import logging
import struct


class Tool(object):

    def __init__(self, args):
        self.args = args

    def run(self):
        print(self.jpeg_length_of_data_after_end_of_image_marker(self.args.path))

    @classmethod
    def jpeg_length_of_data_after_end_of_image_marker2(cls, path):
        with open(path, 'rb') as f:
            ba = f.read()
            eoi_position = ba.rfind(b'\xff\xd9')
            return len(ba) - (eoi_position + 2)

    @classmethod
    def jpeg_length_of_data_after_end_of_image_marker(cls, path):
        with open(path, 'rb') as f:
            ba = f.read()
            position = 0
            total_length = len(ba)
            while position < total_length:
                tag_bytes = ba[position:position + 2]
                position += 2
                if tag_bytes == b'\xff\xd8': # start-of-image
                    length = 0
                else:
                    length, = struct.unpack('>H', ba[position:position + 2])
                logging.debug('Position 0x{0:x}/{0} {1} length 0x{2:x}/{2}'.format(position, ''.join('{:02x}'.format(ord(b)) for b in tag_bytes), length))
                if not length:
                    continue
                position += length
                if tag_bytes == b'\xff\xda': # start-of-sample (start of image data)
                    eoi_position = ba.find(b'\xff\xd9', position)
                    length = eoi_position - position
                    extra_data_length = total_length - (eoi_position + 2)
                    logging.debug('Position 0x{0:x}/{0} {1} length 0x{2:x}/{2}'.format(position, '(image data)', length))
                    logging.debug('Position 0x{0:x}/{0} EOI marker'.format(eoi_position))
                    logging.debug('Extra data after EOI marker length: 0x{0:x}/{0}'.format(extra_data_length))
                    return extra_data_length
        return 0

    @classmethod
    def main(cls):
        parser = argparse.ArgumentParser(description='Determine amount of extra data after end-of-image marker in a JPEG file')
        parser.add_argument('path', help='Path to JPEG file')
        parser.add_argument('-v', '--verbose', action='store_true', help='Enable verbose debug logging')

        args = parser.parse_args()
        if args.verbose:
            logging.basicConfig(level=logging.DEBUG)

        return cls(args).run()


if __name__ == "__main__":
    sys.exit(Tool.main())