Omniglot Dataset (#323)

* Add basic Omniglot dataset loader

* Remove unused import

* Add Omniglot random pair to sample pair of characters

* Precompute random set of pairs, deterministic after object instantiation

* Export OmniglotRandomPair via the datasets module interfact

* Fix naming convention, use sum instead of reduce

* Fix downloading to not download everything, fix Python2 syntax

* Fix end line lint

* Add random_seed, syntax fixes

* Remove randomized pair, take up as a separate generic wrapper

* Fix master conflict

torchvision/datasets/__init__.py

@@ -8,9 +8,11 @@ from .svhn import SVHN
 from .phototour import PhotoTour
 from .fakedata import FakeData
 from .semeion import SEMEION
+from .omniglot import Omniglot
 
 __all__ = ('LSUN', 'LSUNClass',
            'ImageFolder', 'FakeData',
            'CocoCaptions', 'CocoDetection',
            'CIFAR10', 'CIFAR100', 'EMNIST', 'FashionMNIST',
-           'MNIST', 'STL10', 'SVHN', 'PhotoTour', 'SEMEION')
+           'MNIST', 'STL10', 'SVHN', 'PhotoTour', 'SEMEION',
+           'Omniglot')

torchvision/datasets/cifar.py

@@ -2,7 +2,6 @@ from __future__ import print_function
 from PIL import Image
 import os
 import os.path
-import errno
 import numpy as np
 import sys
 if sys.version_info[0] == 2:

torchvision/datasets/omniglot.py

+from __future__ import print_function
+from PIL import Image
+from os.path import join
+import os
+import torch.utils.data as data
+from .utils import download_url, check_integrity, list_dir, list_files
+
+
+class Omniglot(data.Dataset):
+    """`Omniglot <https://github.com/brendenlake/omniglot>`_ Dataset.
+    Args:
+        root (string): Root directory of dataset where directory
+            ``omniglot-py`` exists.
+        background (bool, optional): If True, creates dataset from the "background" set, otherwise
+            creates from the "evaluation" set. This terminology is defined by the authors.
+        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 zip files from the internet and
+            puts it in root directory. If the zip files are already downloaded, they are not
+            downloaded again.
+    """
+    folder = 'omniglot-py'
+    download_url_prefix = 'https://github.com/brendenlake/omniglot/raw/master/python'
+    zips_md5 = {
+        'images_background': '68d2efa1b9178cc56df9314c21c6e718',
+        'images_evaluation': '6b91aef0f799c5bb55b94e3f2daec811'
+    }
+
+    def __init__(self, root, background=True,
+                 transform=None, target_transform=None,
+                 download=False):
+        self.root = join(os.path.expanduser(root), self.folder)
+        self.background = background
+        self.transform = transform
+        self.target_transform = target_transform
+
+        if download:
+            self.download()
+
+        if not self._check_integrity():
+            raise RuntimeError('Dataset not found or corrupted.' +
+                               ' You can use download=True to download it')
+
+        self.target_folder = join(self.root, self._get_target_folder())
+        self._alphabets = list_dir(self.target_folder)
+        self._characters = sum([[join(a, c) for c in list_dir(join(self.target_folder, a))]
+                                for a in self._alphabets], [])
+        self._character_images = [[(image, idx) for image in list_files(join(self.target_folder, character), '.png')]
+                                  for idx, character in enumerate(self._characters)]
+        self._flat_character_images = sum(self._character_images, [])
+
+    def __len__(self):
+        return len(self._flat_character_images)
+
+    def __getitem__(self, index):
+        """
+        Args:
+            index (int): Index
+
+        Returns:
+            tuple: (image, target) where target is index of the target character class.
+        """
+        image_name, character_class = self._flat_character_images[index]
+        image_path = join(self.target_folder, self._characters[character_class], image_name)
+        image = Image.open(image_path, mode='r').convert('L')
+
+        if self.transform:
+            image = self.transform(image)
+
+        if self.target_transform:
+            character_class = self.target_transform(character_class)
+
+        return image, character_class
+
+    def _check_integrity(self):
+        zip_filename = self._get_target_folder()
+        if not check_integrity(join(self.root, zip_filename + '.zip'), self.zips_md5[zip_filename]):
+            return False
+        return True
+
+    def download(self):
+        import zipfile
+
+        if self._check_integrity():
+            print('Files already downloaded and verified')
+            return
+
+        filename = self._get_target_folder()
+        zip_filename = filename + '.zip'
+        url = self.download_url_prefix + '/' + zip_filename
+        download_url(url, self.root, zip_filename, self.zips_md5[filename])
+        print('Extracting downloaded file: ' + join(self.root, zip_filename))
+        with zipfile.ZipFile(join(self.root, zip_filename), 'r') as zip_file:
+            zip_file.extractall(self.root)
+
+    def _get_target_folder(self):
+        return 'images_background' if self.background else 'images_evaluation'

torchvision/datasets/utils.py

@@ -45,3 +45,49 @@ def download_url(url, root, filename, md5):
                 print('Failed download. Trying https -> http instead.'
                       ' Downloading ' + url + ' to ' + fpath)
                 urllib.request.urlretrieve(url, fpath)
+
+
+def list_dir(root, prefix=False):
+    """List all directories at a given root
+
+    Args:
+        root (str): Path to directory whose folders need to be listed
+        prefix (bool, optional): If true, prepends the path to each result, otherwise
+            only returns the name of the directories found
+    """
+    root = os.path.expanduser(root)
+    directories = list(
+        filter(
+            lambda p: os.path.isdir(os.path.join(root, p)),
+            os.listdir(root)
+        )
+    )
+
+    if prefix is True:
+        directories = [os.path.join(root, d) for d in directories]
+
+    return directories
+
+
+def list_files(root, suffix, prefix=False):
+    """List all files ending with a suffix at a given root
+
+    Args:
+        root (str): Path to directory whose folders need to be listed
+        suffix (str or tuple): Suffix of the files to match, e.g. '.png' or ('.jpg', '.png').
+            It uses the Python "str.endswith" method and is passed directly
+        prefix (bool, optional): If true, prepends the path to each result, otherwise
+            only returns the name of the files found
+    """
+    root = os.path.expanduser(root)
+    files = list(
+        filter(
+            lambda p: os.path.isfile(os.path.join(root, p)) and p.endswith(suffix),
+            os.listdir(root)
+        )
+    )
+
+    if prefix is True:
+        files = [os.path.join(root, d) for d in files]
+
+    return files