qr.py

from argparse import ArgumentParser
from math import sqrt
from urllib import urlencode
import sys


MAX_SIZE = 300000


def main():
    parser = ArgumentParser(
        description='Generate a QR code using Google Chart Tools.')
    parser.add_argument('--encoding',
        choices=['UTF-8', 'Shift_JIS', 'ISO-8859-1'], default='UTF-8')
    parser.add_argument('--height', type=int)
    parser.add_argument('--level', choices='LMQH', default='L')
    parser.add_argument('--margin', default=4, type=int)
    parser.add_argument('--width', type=int)
    parser.add_argument('data')
    args = parser.parse_args()

    if args.height is None and args.width is None:
        args.height = args.width = 512
    elif args.height is not None and args.width is None:
        args.width = args.height
    elif args.width is not None and args.height is None:
        args.height = args.width

    if args.width * args.height > MAX_SIZE:
        ratio = args.width / float(args.height)
        args.width = int(sqrt(MAX_SIZE * ratio))
        args.height = int(sqrt(MAX_SIZE / ratio))

    print '{url}?{parameters}'.format(
        url='https://chart.googleapis.com/chart',
        parameters=urlencode({
            'cht': 'qr',
            'chs': '{width}x{height}'.format(
                width=args.width, height=args.height),
            'chl': args.data,
            'choe': args.encoding,
            'chld': '{level}|{margin}'.format(
                level=args.level, margin=args.margin),
        }),
    )


if __name__ == '__main__':
    sys.exit(main())