def ensemble_vote(int_img, classifiers, alpha):
    """
    Strong classifier: classifies given integral image (numpy array) using given classifiers, 
    i.e. if the sum of all classifier votes is greater 0, image is classified
    positively (1) else negatively (0). The threshold is 0, because votes can be
    +1 or -1.
    :param int_img: Integral image to be classified
    :type int_img: numpy.ndarray
    :param classifiers: List of classifiers
    :type classifiers: list[violajones.HaarLikeFeature.HaarLikeFeature]
    :return: 1 iff sum of classifier votes is greater 0, else 0
    :rtype: int
    """
    
    return 1 if sum([alpha[i] * c.get_vote(int_img) for i, c in enumerate(classifiers)]) > 0.5 * sum(alpha) else 0