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| # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved. | |
| from __future__ import division | |
| import torch | |
| 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, image_sizes): | |
| """ | |
| Arguments: | |
| tensors (tensor) | |
| image_sizes (list[tuple[int, int]]) | |
| """ | |
| self.tensors = tensors | |
| self.image_sizes = image_sizes | |
| def to(self, *args, **kwargs): | |
| cast_tensor = self.tensors.to(*args, **kwargs) | |
| return ImageList(cast_tensor, self.image_sizes) | |
| def to_image_list(tensors, size_divisible=0): | |
| """ | |
| tensors can be an ImageList, a torch.Tensor or | |
| an iterable of Tensors. It can't be a numpy array. | |
| When tensors is an iterable of Tensors, it pads | |
| the Tensors with zeros so that they have the same | |
| shape | |
| """ | |
| if isinstance(tensors, torch.Tensor) and size_divisible > 0: | |
| tensors = [tensors] | |
| if isinstance(tensors, ImageList): | |
| return tensors | |
| elif isinstance(tensors, torch.Tensor): | |
| # single tensor shape can be inferred | |
| assert tensors.dim() == 4 | |
| image_sizes = [tensor.shape[-2:] for tensor in tensors] | |
| return ImageList(tensors, image_sizes) | |
| elif isinstance(tensors, (tuple, list)): | |
| max_size = tuple(max(s) for s in zip(*[img.shape for img in tensors])) | |
| # TODO Ideally, just remove this and let me model handle arbitrary | |
| # input sizs | |
| if size_divisible > 0: | |
| import math | |
| stride = size_divisible | |
| max_size = list(max_size) | |
| max_size[1] = int(math.ceil(max_size[1] / stride) * stride) | |
| max_size[2] = int(math.ceil(max_size[2] / stride) * stride) | |
| max_size = tuple(max_size) | |
| batch_shape = (len(tensors),) + max_size | |
| batched_imgs = tensors[0].new(*batch_shape).zero_() | |
| for img, pad_img in zip(tensors, batched_imgs): | |
| pad_img[: img.shape[0], : img.shape[1], : img.shape[2]].copy_(img) | |
| image_sizes = [im.shape[-2:] for im in tensors] | |
| return ImageList(batched_imgs, image_sizes) | |
| else: | |
| raise TypeError("Unsupported type for to_image_list: {}".format(type(tensors))) | |