# Copyright (c) 2021-2022, NVIDIA CORPORATION. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#           http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import torch
from torch import Tensor
from typing import List, Tuple


class ImageList(object):
    """
    Structure that holds a list of images (of possibly
    varying sizes) as a single tensor.
    This works by padding the images to the same size,
    and storing in a field the original sizes of each image
    """

    def __init__(self, tensors: Tensor, image_sizes: List[Tuple[int, int]]):
        """
        Args:
            tensors (tensor)
            image_sizes (list[tuple[int, int]])
        """
        self.tensors = tensors
        self.image_sizes = image_sizes

    def to(self, device: torch.device) -> 'ImageList':
        cast_tensor = self.tensors.to(device)
        return ImageList(cast_tensor, self.image_sizes)