import numpy as np


def intersection_over_union(pred, true):
    """
    Calculates intersection and union for a batch of images.

    Args:
        pred (torch.Tensor): a tensor of predictions
        true (torc.Tensor): a tensor of labels

    Returns:
        intersection (int): total intersection of pixels
        union (int): total union of pixels
    """
    valid_pixel_mask = true.ne(255)  # valid pixel mask
    true = true.masked_select(valid_pixel_mask).to("cpu")
    pred = pred.masked_select(valid_pixel_mask).to("cpu")

    # Intersection and union totals
    intersection = np.logical_and(true, pred)
    union = np.logical_or(true, pred)
    return intersection.sum() / union.sum()