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import os
import torch
import torch.nn
import numpy as np
from PIL import Image
from skimage.io import imread
import torchvision.transforms as transforms
from torch.utils.data import Dataset, DataLoader
from sklearn.model_selection import train_test_split
def read_IAM_label_txt_file(file_txt_labels):
"""
---------
Arguments
---------
file_txt_labels : str
full path to the text file containing labels
-------
Returns
-------
a tuple of
all_image_files : list
a list of all image file names
all_labels : list
a list of all labels
"""
label_file_handler = open(file_txt_labels, mode="r")
all_lines = label_file_handler.readlines()
num_lines = len(all_lines)
all_image_files = []
all_labels = []
for cur_line_num in range(num_lines):
if cur_line_num % 3 == 0:
all_image_files.append(all_lines[cur_line_num].strip())
elif cur_line_num % 3 == 1:
all_labels.append(all_lines[cur_line_num].strip())
else:
continue
return all_image_files, all_labels
class HWRecogIAMDataset(Dataset):
"""
Main dataset class to be used only for training, validation and internal testing
"""
CHAR_SET = ' !"#&\'()*+,-./0123456789:;?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
CHAR_2_LABEL = {char: i + 1 for i, char in enumerate(CHAR_SET)}
LABEL_2_CHAR = {label: char for char, label in CHAR_2_LABEL.items()}
def __init__(self, list_image_files, list_labels, dir_images, image_height=32, image_width=768, which_set="train"):
"""
---------
Arguments
---------
list_image_files : list
list of image files
list_labels : list
list of labels
dir_images : str
full path to directory containing images
image_height : int
image height (default: 32)
image_width : int
image width (default: 768)
which_set : str
a string indicating which set is being used (default: train)
"""
self.list_labels = list_labels
self.dir_images = dir_images
self.list_image_files = list_image_files
self.image_width = image_width
self.image_height = image_height
self.which_set = which_set
if self.which_set == "train":
# apply data augmentation only for train set
self.transform = transforms.Compose([
transforms.ToPILImage(),
transforms.Resize((self.image_height, self.image_width), Image.BILINEAR),
transforms.RandomAffine(degrees=[-0.75, 0.75], translate=[0, 0.05], scale=[0.75, 1],
shear=[-35, 35], interpolation=transforms.InterpolationMode.BILINEAR, fill=255,
),
transforms.ToTensor(),
transforms.Normalize(
mean=[0.485, 0.456, 0.406],
std=[0.229, 0.224, 0.225],
),
])
else:
self.transform = transforms.Compose([
transforms.ToPILImage(),
transforms.Resize((self.image_height, self.image_width), Image.BILINEAR),
transforms.ToTensor(),
transforms.Normalize(
mean=[0.485, 0.456, 0.406],
std=[0.229, 0.224, 0.225],
),
])
def __len__(self):
return len(self.list_image_files)
def __getitem__(self, idx):
image_file_name = self.list_image_files[idx]
image_gray = imread(os.path.join(self.dir_images, image_file_name))
image_3_channel = np.repeat(np.expand_dims(image_gray, -1), 3, -1)
image_3_channel = self.transform(image_3_channel)
label_string = self.list_labels[idx]
label_encoded = [self.CHAR_2_LABEL[c] for c in label_string]
label_length = [len(label_encoded)]
label_encoded = torch.LongTensor(label_encoded)
label_length = torch.LongTensor(label_length)
return image_3_channel, label_encoded, label_length
def IAM_collate_fn(batch):
"""
collate function
---------
Arguments
---------
batch : tuple
a batch of input data as a tuple
-------
Returns
-------
a collated tuple of
images : tensor
tensor of batch images
labels : tensor
tensor of batch labels
label_lengths : tensor
tensor of batch label lengths
"""
images, labels, label_lengths = zip(*batch)
images = torch.stack(images, 0)
labels = torch.cat(labels, 0)
label_lengths = torch.cat(label_lengths, 0)
return images, labels, label_lengths
def split_dataset(file_txt_labels, for_train=True):
"""
---------
Arguments
---------
file_txt_labels : str
full path to the text file containing labels
for_train : bool
indicating whether split is for training or internal testing
-------
Returns
-------
a tuple of files depending for train or internal testing
"""
all_image_files, all_labels = read_IAM_label_txt_file(file_txt_labels)
train_image_files, test_image_files, train_labels, test_labels = train_test_split(all_image_files, all_labels, test_size=0.1, random_state=4)
train_image_files, valid_image_files, train_labels, valid_labels = train_test_split(train_image_files, train_labels, test_size=0.1, random_state=4)
if for_train:
return train_image_files, valid_image_files, train_labels, valid_labels
else:
return test_image_files, test_labels
def get_dataloaders_for_training(train_x, train_y, valid_x, valid_y, dir_images, image_height=32, image_width=768, batch_size=8):
"""
---------
Arguments
---------
train_x : list
list of train file names
train_y : list
list of train labels
valid_x : list
list of validation file names
valid_y : list
list of validation labels
dir_images : str
full directory path containing the images
image_height : int
image height (default: 32)
image_width : int
image width (default: 768)
batch_size : int
batch size (default: 8)
-------
Returns
-------
a tuple of dataloaders objects
train_loader : object
object of train set dataloader
valid_loader : object
object of validation set dataloader
"""
train_dataset = HWRecogIAMDataset(train_x, train_y, dir_images, image_height=image_height, image_width=image_width, which_set="train")
valid_dataset = HWRecogIAMDataset(valid_x, valid_y, dir_images, image_height=image_height, image_width=image_width, which_set="valid")
train_loader = DataLoader(
train_dataset,
batch_size=batch_size,
shuffle=True,
num_workers=4,
collate_fn=IAM_collate_fn,
)
valid_loader = DataLoader(
valid_dataset,
batch_size=batch_size,
shuffle=False,
num_workers=4,
collate_fn=IAM_collate_fn,
)
return train_loader, valid_loader
def get_dataloader_for_testing(test_x, test_y, dir_images, image_height=32, image_width=768, batch_size=1):
"""
---------
Arguments
---------
test_x : list
list of test file names
test_y : list
list of test labels
dir_images : str
full directory path containing the images
image_height : int
image height (default: 32)
image_width : int
image width (default: 768)
batch_size : int
batch size (default: 1)
-------
Returns
-------
test_loader : object
object of test set dataloader
"""
test_dataset = HWRecogIAMDataset(test_x, test_y, dir_images=dir_images, image_height=image_height, image_width=image_width, which_set="test")
test_loader = DataLoader(
test_dataset,
batch_size=batch_size,
shuffle=False,
num_workers=4,
collate_fn=IAM_collate_fn,
)
return test_loader
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