cng2jpg.py

#!/usr/bin/python
"""Convert "Complete National Geographic" CNG files to JPG for use under Linux

cng2jpg.py --src /run/media/user/CNG_DISC1/disc1/images --dst ~/CNG/discs/images
"""

import os
import argparse


def convert_one(src_filename, dst_filename):
    """Convert source file by performing a byte-by-byte xor 239, save result into new file

    :param src_filename: source filename, will be opened read-only
    :param dst_filename: destination file, will be truncated if exists
    """
    print (dst_filename)
    with open(src_filename, 'rb') as in_stream, open(dst_filename, 'wb') as out_stream:
        out_stream.write(bytearray((c ^ 239) for c in in_stream.read()))


def convert_all(src_path, dst_path, remove=False):
    """Recursively convert all .cng files found in src_path.

    Converted .cng files are saved as <file>.jpg under dst_path.
    Intermediary subdirectories will be created as necessary to preserve the directory structure.

    :param src_path: source directory (must exist)
    :param dst_path: target directory, can be same as source (will be created if missing)
    :param remove: if True, remove original .cng files as they are converted. Use if data was
                   already copied from CDs to local drive, to avoid needing extra 48Gb of space.
    """
    for root, dirs, files in os.walk(src_path):
        target_path = root.replace(src_path, dst_path, 1)
        for filename in files:
            basename, ext = os.path.splitext(filename)
            if ext.lower() == '.cng':
                if not os.path.exists(target_path):
                    os.makedirs(target_path)
                dst_filename = os.path.join(target_path, basename + ".jpg")
                src_filename = os.path.join(root, filename)
                convert_one(src_filename, dst_filename)
                if remove:
                    os.remove(src_filename)


def main():
    parser = argparse.ArgumentParser(description='Convert NatGeo CNG files to JPG')
    parser.add_argument('-s', '--src', required=True,
                        help='path to source directory containing files to convert')
    parser.add_argument('-d', '--dst', required=False,
                        help='optional destination path (default in-place)')
    parser.add_argument('-r', '--remove', action='store_true', default=False,
                        help='remove original cng files after conversion')
    args = parser.parse_args()

    if args.dst and not os.path.exists(args.dst):
        os.makedirs(args.dst)

    convert_all(args.src, args.dst or args.src, remove=args.remove)


if __name__ == '__main__':
    main()