def METHOD_NAME(num_items, bboxes, img_w, img_h):
    rng = np.random.RandomState(0)
    masks = np.zeros((num_items, img_h, img_w))
    for i, bbox in enumerate(bboxes):
        bbox = bbox.astype(np.int32)
        mask = (rng.rand(1, bbox[3] - bbox[1], bbox[2] - bbox[0]) >
                0.3).astype(np.int64)
        masks[i:i + 1, bbox[1]:bbox[3], bbox[0]:bbox[2]] = mask
    return BitmapMasks(masks, height=img_h, width=img_w)