import os import random from argparse import ArgumentParser, Namespace import numpy as np import torch import torch.nn.functional as F import torchvision.transforms as transforms from PIL import Image from torch.utils.data import DataLoader, Dataset import pytorch_lightning as pl from pl_examples.models.unet import UNet from pytorch_lightning.loggers import WandbLogger DEFAULT_VOID_LABELS = (0, 1, 2, 3, 4, 5, 6, 9, 10, 14, 15, 16, 18, 29, 30, -1) DEFAULT_VALID_LABELS = (7, 8, 11, 12, 13, 17, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 31, 32, 33) class KITTI(Dataset): """ Class for KITTI Semantic Segmentation Benchmark dataset Dataset link - http://www.cvlibs.net/datasets/kitti/eval_semseg.php?benchmark=semantics2015 There are 34 classes in the given labels. However, not all of them are useful for training (like railings on highways, road dividers, etc.). So, these useless classes (the pixel values of these classes) are stored in the `void_labels`. The useful classes are stored in the `valid_labels`. The `encode_segmap` function sets all pixels with any of the `void_labels` to `ignore_index` (250 by default). It also sets all of the valid pixels to the appropriate value between 0 and `len(valid_labels)` (since that is the number of valid classes), so it can be used properly by the loss function when comparing with the output. The `get_filenames` function retrieves the filenames of all images in the given `path` and saves the absolute path in a list. In the `get_item` function, images and masks are resized to the given `img_size`, masks are encoded using `encode_segmap`, and given `transform` (if any) are applied to the image only (mask does not usually require transforms, but they can be implemented in a similar way). """ IMAGE_PATH = os.path.join('training', 'image_2') MASK_PATH = os.path.join('training', 'semantic') def __init__( self, data_path: str, split: str, img_size: tuple = (1242, 376), void_labels: list = DEFAULT_VOID_LABELS, valid_labels: list = DEFAULT_VALID_LABELS, transform=None ): self.img_size = img_size self.void_labels = void_labels self.valid_labels = valid_labels self.ignore_index = 250 self.class_map = dict(zip(self.valid_labels, range(len(self.valid_labels)))) self.transform = transform self.split = split self.data_path = data_path self.img_path = os.path.join(self.data_path, self.IMAGE_PATH) self.mask_path = os.path.join(self.data_path, self.MASK_PATH) self.img_list = self.get_filenames(self.img_path) self.mask_list = self.get_filenames(self.mask_path) # Split between train and valid set (80/20) random_inst = random.Random(12345) # for repeatability n_items = len(self.img_list) idxs = random_inst.sample(range(n_items), n_items // 5) if self.split == 'train': idxs = [idx for idx in range(n_items) if idx not in idxs] self.img_list = [self.img_list[i] for i in idxs] self.mask_list = [self.mask_list[i] for i in idxs] def __len__(self): return len(self.img_list) def __getitem__(self, idx): img = Image.open(self.img_list[idx]) img = img.resize(self.img_size) img = np.array(img) mask = Image.open(self.mask_list[idx]).convert('L') mask = mask.resize(self.img_size) mask = np.array(mask) mask = self.encode_segmap(mask) if self.transform: img = self.transform(img) return img, mask def encode_segmap(self, mask): """ Sets void classes to zero so they won't be considered for training """ for voidc in self.void_labels: mask[mask == voidc] = self.ignore_index for validc in self.valid_labels: mask[mask == validc] = self.class_map[validc] # remove extra idxs from updated dataset mask[mask > 18] = self.ignore_index return mask def get_filenames(self, path): """ Returns a list of absolute paths to images inside given `path` """ files_list = list() for filename in os.listdir(path): files_list.append(os.path.join(path, filename)) return files_list class SegModel(pl.LightningModule): """ Semantic Segmentation Module This is a basic semantic segmentation module implemented with Lightning. It uses CrossEntropyLoss as the default loss function. May be replaced with other loss functions as required. It is specific to KITTI dataset i.e. dataloaders are for KITTI and Normalize transform uses the mean and standard deviation of this dataset. It uses the FCN ResNet50 model as an example. Adam optimizer is used along with Cosine Annealing learning rate scheduler. """ def __init__(self, data_path: str, batch_size: int, lr: float, num_layers: int, features_start: int, bilinear: bool, **kwargs): super().__init__() self.data_path = data_path self.batch_size = batch_size self.lr = lr self.num_layers = num_layers self.features_start = features_start self.bilinear = bilinear self.net = UNet(num_classes=19, num_layers=self.num_layers, features_start=self.features_start, bilinear=self.bilinear) self.transform = transforms.Compose([ transforms.ToTensor(), transforms.Normalize(mean=[0.35675976, 0.37380189, 0.3764753], std=[0.32064945, 0.32098866, 0.32325324]) ]) self.trainset = KITTI(self.data_path, split='train', transform=self.transform) self.validset = KITTI(self.data_path, split='valid', transform=self.transform) def forward(self, x): return self.net(x) def training_step(self, batch, batch_nb): img, mask = batch img = img.float() mask = mask.long() out = self(img) loss_val = F.cross_entropy(out, mask, ignore_index=250) log_dict = {'train_loss': loss_val} return {'loss': loss_val, 'log': log_dict, 'progress_bar': log_dict} def validation_step(self, batch, batch_idx): img, mask = batch img = img.float() mask = mask.long() out = self(img) loss_val = F.cross_entropy(out, mask, ignore_index=250) return {'val_loss': loss_val} def validation_epoch_end(self, outputs): loss_val = torch.stack([x['val_loss'] for x in outputs]).mean() log_dict = {'val_loss': loss_val} return {'log': log_dict, 'val_loss': log_dict['val_loss'], 'progress_bar': log_dict} def configure_optimizers(self): opt = torch.optim.Adam(self.net.parameters(), lr=self.learning_rate) sch = torch.optim.lr_scheduler.CosineAnnealingLR(opt, T_max=10) return [opt], [sch] def train_dataloader(self): return DataLoader(self.trainset, batch_size=self.batch_size, shuffle=True) def val_dataloader(self): return DataLoader(self.validset, batch_size=self.batch_size, shuffle=False) def main(hparams: Namespace): # ------------------------ # 1 INIT LIGHTNING MODEL # ------------------------ model = SegModel(**vars(hparams)) # ------------------------ # 2 SET LOGGER # ------------------------ logger = False if hparams.log_wandb: logger = WandbLogger() # optional: log model topology logger.watch(model.net) # ------------------------ # 3 INIT TRAINER # ------------------------ trainer = pl.Trainer( gpus=hparams.gpus, logger=logger, max_epochs=hparams.epochs, accumulate_grad_batches=hparams.grad_batches, distributed_backend=hparams.distributed_backend, precision=16 if hparams.use_amp else 32, ) # ------------------------ # 5 START TRAINING # ------------------------ trainer.fit(model) if __name__ == '__main__': parser = ArgumentParser() parser.add_argument("--data_path", type=str, help="path where dataset is stored") parser.add_argument("--gpus", type=int, default=-1, help="number of available GPUs") parser.add_argument('--distributed-backend', type=str, default='dp', choices=('dp', 'ddp', 'ddp2'), help='supports three options dp, ddp, ddp2') parser.add_argument('--use_amp', action='store_true', help='if true uses 16 bit precision') parser.add_argument("--batch_size", type=int, default=4, help="size of the batches") parser.add_argument("--lr", type=float, default=0.001, help="adam: learning rate") parser.add_argument("--num_layers", type=int, default=5, help="number of layers on u-net") parser.add_argument("--features_start", type=float, default=64, help="number of features in first layer") parser.add_argument("--bilinear", action='store_true', default=False, help="whether to use bilinear interpolation or transposed") parser.add_argument("--grad_batches", type=int, default=1, help="number of batches to accumulate") parser.add_argument("--epochs", type=int, default=20, help="number of epochs to train") parser.add_argument("--log_wandb", action='store_true', help="log training on Weights & Biases") hparams = parser.parse_args() main(hparams)