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omniglot.py
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omniglot.py
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# Adapted from https://github.com/pytorch/vision/blob/master/torchvision/datasets/omniglot.py
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'
def loadimgs(path,n = 0):
'''
path => Path of train directory or test directory
'''
X=[]
y = []
cat_dict = {}
lang_dict = {}
curr_y = n
# we load every alphabet seperately so we can isolate them later
for alphabet in os.listdir(path):
print("loading alphabet: " + alphabet)
lang_dict[alphabet] = [curr_y,None]
alphabet_path = os.path.join(path,alphabet)
# every letter/category has it's own column in the array, so load seperately
for letter in os.listdir(alphabet_path):
cat_dict[curr_y] = (alphabet, letter)
category_images=[]
letter_path = os.path.join(alphabet_path, letter)
# read all the images in the current category
for filename in os.listdir(letter_path):
image_path = os.path.join(letter_path, filename)
image = imread(image_path)
category_images.append(image)
y.append(curr_y)
try:
X.append(np.stack(category_images))
# edge case - last one
except ValueError as e:
print(e)
print("error - category_images:", category_images)
curr_y += 1
lang_dict[alphabet][1] = curr_y - 1
y = np.vstack(y)
X = np.stack(X)
return X,y,lang_dict
def get_batch(batch_size,s="train"):
"""
Create batch of n pairs, half same class, half different class
"""
if s == 'train':
X = Xtrain
categories = train_classes
else:
X = Xval
categories = val_classes
n_classes, n_examples, w, h = X.shape
# randomly sample several classes to use in the batch
categories = rng.choice(n_classes,size=(batch_size,),replace=False)
# initialize 2 empty arrays for the input image batch
pairs=[np.zeros((batch_size, h, w,1)) for i in range(2)]
# initialize vector for the targets
targets=np.zeros((batch_size,))
# make one half of it '1's, so 2nd half of batch has same class
targets[batch_size//2:] = 1
for i in range(batch_size):
category = categories[i]
idx_1 = rng.randint(0, n_examples)
pairs[0][i,:,:,:] = X[category, idx_1].reshape(w, h, 1)
idx_2 = rng.randint(0, n_examples)
# pick images of same class for 1st half, different for 2nd
if i >= batch_size // 2:
category_2 = category
else:
# add a random number to the category modulo n classes to ensure 2nd image has a different category
category_2 = (category + rng.randint(1,n_classes)) % n_classes
pairs[1][i,:,:,:] = X[category_2,idx_2].reshape(w, h,1)
return pairs, targets