@staticmethod
def parse_size(size):
    """
        Parses size string into a tuple

        :param size: String on the form '100', 'x100 or '100x200'
        :return: Tuple of two integers for width and height
        :rtype: tuple
        """
    if size.startswith('x'):
        return None, int(size.replace('x', ''))
    if 'x' in size:
        return int(size.split('x')[0]), int(size.split('x')[1])
    return int(size), None
