Source code for torchvision.datasets.svhn
import os.path
from typing import Any, Callable, Optional, Tuple
import numpy as np
from PIL import Image
from .utils import check_integrity, download_url, verify_str_arg
from .vision import VisionDataset
[docs]class SVHN(VisionDataset):
"""`SVHN <http://ufldl.stanford.edu/housenumbers/>`_ Dataset.
Note: The SVHN dataset assigns the label `10` to the digit `0`. However, in this Dataset,
we assign the label `0` to the digit `0` to be compatible with PyTorch loss functions which
expect the class labels to be in the range `[0, C-1]`
.. warning::
This class needs `scipy <https://docs.scipy.org/doc/>`_ to load data from `.mat` format.
Args:
root (string): Root directory of the dataset where the data is stored.
split (string): One of {'train', 'test', 'extra'}.
Accordingly dataset is selected. 'extra' is Extra training set.
transform (callable, optional): A function/transform that takes in an PIL image
and returns a transformed version. E.g, ``transforms.RandomCrop``
target_transform (callable, optional): A function/transform that takes in the
target and transforms it.
download (bool, optional): If true, downloads the dataset from the internet and
puts it in root directory. If dataset is already downloaded, it is not
downloaded again.
"""
split_list = {
"train": [
"http://ufldl.stanford.edu/housenumbers/train_32x32.mat",
"train_32x32.mat",
"e26dedcc434d2e4c54c9b2d4a06d8373",
],
"test": [
"http://ufldl.stanford.edu/housenumbers/test_32x32.mat",
"test_32x32.mat",
"eb5a983be6a315427106f1b164d9cef3",
],
"extra": [
"http://ufldl.stanford.edu/housenumbers/extra_32x32.mat",
"extra_32x32.mat",
"a93ce644f1a588dc4d68dda5feec44a7",
],
}
def __init__(
self,
root: str,
split: str = "train",
transform: Optional[Callable] = None,
target_transform: Optional[Callable] = None,
download: bool = False,
) -> None:
super().__init__(root, transform=transform, target_transform=target_transform)
self.split = verify_str_arg(split, "split", tuple(self.split_list.keys()))
self.url = self.split_list[split][0]
self.filename = self.split_list[split][1]
self.file_md5 = self.split_list[split][2]
if download:
self.download()
if not self._check_integrity():
raise RuntimeError("Dataset not found or corrupted. You can use download=True to download it")
# import here rather than at top of file because this is
# an optional dependency for torchvision
import scipy.io as sio
# reading(loading) mat file as array
loaded_mat = sio.loadmat(os.path.join(self.root, self.filename))
self.data = loaded_mat["X"]
# loading from the .mat file gives an np array of type np.uint8
# converting to np.int64, so that we have a LongTensor after
# the conversion from the numpy array
# the squeeze is needed to obtain a 1D tensor
self.labels = loaded_mat["y"].astype(np.int64).squeeze()
# the svhn dataset assigns the class label "10" to the digit 0
# this makes it inconsistent with several loss functions
# which expect the class labels to be in the range [0, C-1]
np.place(self.labels, self.labels == 10, 0)
self.data = np.transpose(self.data, (3, 2, 0, 1))
[docs] def __getitem__(self, index: int) -> Tuple[Any, Any]:
"""
Args:
index (int): Index
Returns:
tuple: (image, target) where target is index of the target class.
"""
img, target = self.data[index], int(self.labels[index])
# doing this so that it is consistent with all other datasets
# to return a PIL Image
img = Image.fromarray(np.transpose(img, (1, 2, 0)))
if self.transform is not None:
img = self.transform(img)
if self.target_transform is not None:
target = self.target_transform(target)
return img, target
def __len__(self) -> int:
return len(self.data)
def _check_integrity(self) -> bool:
root = self.root
md5 = self.split_list[self.split][2]
fpath = os.path.join(root, self.filename)
return check_integrity(fpath, md5)
def download(self) -> None:
md5 = self.split_list[self.split][2]
download_url(self.url, self.root, self.filename, md5)
def extra_repr(self) -> str:
return "Split: {split}".format(**self.__dict__)