luna_image.py 文件源码

def weight_by_class_balance(truth, classes=None):
    """
    Determines a loss weight map given the truth by balancing the classes from the classes argument.
    The classes argument can be used to only include certain classes (you may for instance want to exclude the background).
    """

    if classes is None:
        # Include all classes
        classes = np.unique(truth)

    weight_map = np.zeros_like(truth, dtype=np.float32)
    total_amount = np.product(truth.shape)

    min_weight = sys.maxint
    for c in classes:
        class_mask = np.where(truth==c,1,0)
        class_weight = 1/((np.sum(class_mask)+1e-8)/total_amount)
        if class_weight < min_weight:
            min_weight = class_weight
        weight_map += (class_mask*class_weight)#/total_amount
    weight_map /= min_weight
    return weight_map