update

ultralytics/models/yolo/classify/__init__.py

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+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+from ultralytics.models.yolo.classify.predict import ClassificationPredictor
+from ultralytics.models.yolo.classify.train import ClassificationTrainer
+from ultralytics.models.yolo.classify.val import ClassificationValidator
+
+__all__ = "ClassificationPredictor", "ClassificationTrainer", "ClassificationValidator"

ultralytics/models/yolo/classify/predict.py

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+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+import cv2
+import torch
+from PIL import Image
+
+from ultralytics.engine.predictor import BasePredictor
+from ultralytics.engine.results import Results
+from ultralytics.utils import DEFAULT_CFG, ops
+
+
+class ClassificationPredictor(BasePredictor):
+    """
+    A class extending the BasePredictor class for prediction based on a classification model.
+
+    Notes:
+        - Torchvision classification models can also be passed to the 'model' argument, i.e. model='resnet18'.
+
+    Example:
+        ```python
+        from ultralytics.utils import ASSETS
+        from ultralytics.models.yolo.classify import ClassificationPredictor
+
+        args = dict(model='yolov8n-cls.pt', source=ASSETS)
+        predictor = ClassificationPredictor(overrides=args)
+        predictor.predict_cli()
+        ```
+    """
+
+    def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
+        """Initializes ClassificationPredictor setting the task to 'classify'."""
+        super().__init__(cfg, overrides, _callbacks)
+        self.args.task = "classify"
+        self._legacy_transform_name = "ultralytics.yolo.data.augment.ToTensor"
+
+    def preprocess(self, img):
+        """Converts input image to model-compatible data type."""
+        if not isinstance(img, torch.Tensor):
+            is_legacy_transform = any(
+                self._legacy_transform_name in str(transform) for transform in self.transforms.transforms
+            )
+            if is_legacy_transform:  # to handle legacy transforms
+                img = torch.stack([self.transforms(im) for im in img], dim=0)
+            else:
+                img = torch.stack(
+                    [self.transforms(Image.fromarray(cv2.cvtColor(im, cv2.COLOR_BGR2RGB))) for im in img], dim=0
+                )
+        img = (img if isinstance(img, torch.Tensor) else torch.from_numpy(img)).to(self.model.device)
+        return img.half() if self.model.fp16 else img.float()  # uint8 to fp16/32
+
+    def postprocess(self, preds, img, orig_imgs):
+        """Post-processes predictions to return Results objects."""
+        if not isinstance(orig_imgs, list):  # input images are a torch.Tensor, not a list
+            orig_imgs = ops.convert_torch2numpy_batch(orig_imgs)
+
+        results = []
+        for i, pred in enumerate(preds):
+            orig_img = orig_imgs[i]
+            img_path = self.batch[0][i]
+            results.append(Results(orig_img, path=img_path, names=self.model.names, probs=pred))
+        return results

ultralytics/models/yolo/classify/train.py

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+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+import torch
+import torchvision
+
+from ultralytics.data import ClassificationDataset, build_dataloader
+from ultralytics.engine.trainer import BaseTrainer
+from ultralytics.models import yolo
+from ultralytics.nn.tasks import ClassificationModel, attempt_load_one_weight
+from ultralytics.utils import DEFAULT_CFG, LOGGER, RANK, colorstr
+from ultralytics.utils.plotting import plot_images, plot_results
+from ultralytics.utils.torch_utils import is_parallel, strip_optimizer, torch_distributed_zero_first
+
+
+class ClassificationTrainer(BaseTrainer):
+    """
+    A class extending the BaseTrainer class for training based on a classification model.
+
+    Notes:
+        - Torchvision classification models can also be passed to the 'model' argument, i.e. model='resnet18'.
+
+    Example:
+        ```python
+        from ultralytics.models.yolo.classify import ClassificationTrainer
+
+        args = dict(model='yolov8n-cls.pt', data='imagenet10', epochs=3)
+        trainer = ClassificationTrainer(overrides=args)
+        trainer.train()
+        ```
+    """
+
+    def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
+        """Initialize a ClassificationTrainer object with optional configuration overrides and callbacks."""
+        if overrides is None:
+            overrides = {}
+        overrides["task"] = "classify"
+        if overrides.get("imgsz") is None:
+            overrides["imgsz"] = 224
+        super().__init__(cfg, overrides, _callbacks)
+
+    def set_model_attributes(self):
+        """Set the YOLO model's class names from the loaded dataset."""
+        self.model.names = self.data["names"]
+
+    def get_model(self, cfg=None, weights=None, verbose=True):
+        """Returns a modified PyTorch model configured for training YOLO."""
+        model = ClassificationModel(cfg, nc=self.data["nc"], verbose=verbose and RANK == -1)
+        if weights:
+            model.load(weights)
+
+        for m in model.modules():
+            if not self.args.pretrained and hasattr(m, "reset_parameters"):
+                m.reset_parameters()
+            if isinstance(m, torch.nn.Dropout) and self.args.dropout:
+                m.p = self.args.dropout  # set dropout
+        for p in model.parameters():
+            p.requires_grad = True  # for training
+        return model
+
+    def setup_model(self):
+        """Load, create or download model for any task."""
+        if isinstance(self.model, torch.nn.Module):  # if model is loaded beforehand. No setup needed
+            return
+
+        model, ckpt = str(self.model), None
+        # Load a YOLO model locally, from torchvision, or from Ultralytics assets
+        if model.endswith(".pt"):
+            self.model, ckpt = attempt_load_one_weight(model, device="cpu")
+            for p in self.model.parameters():
+                p.requires_grad = True  # for training
+        elif model.split(".")[-1] in ("yaml", "yml"):
+            self.model = self.get_model(cfg=model)
+        elif model in torchvision.models.__dict__:
+            self.model = torchvision.models.__dict__[model](weights="IMAGENET1K_V1" if self.args.pretrained else None)
+        else:
+            raise FileNotFoundError(f"ERROR: model={model} not found locally or online. Please check model name.")
+        ClassificationModel.reshape_outputs(self.model, self.data["nc"])
+
+        return ckpt
+
+    def build_dataset(self, img_path, mode="train", batch=None):
+        """Creates a ClassificationDataset instance given an image path, and mode (train/test etc.)."""
+        return ClassificationDataset(root=img_path, args=self.args, augment=mode == "train", prefix=mode)
+
+    def get_dataloader(self, dataset_path, batch_size=16, rank=0, mode="train"):
+        """Returns PyTorch DataLoader with transforms to preprocess images for inference."""
+        with torch_distributed_zero_first(rank):  # init dataset *.cache only once if DDP
+            dataset = self.build_dataset(dataset_path, mode)
+
+        loader = build_dataloader(dataset, batch_size, self.args.workers, rank=rank)
+        # Attach inference transforms
+        if mode != "train":
+            if is_parallel(self.model):
+                self.model.module.transforms = loader.dataset.torch_transforms
+            else:
+                self.model.transforms = loader.dataset.torch_transforms
+        return loader
+
+    def preprocess_batch(self, batch):
+        """Preprocesses a batch of images and classes."""
+        batch["img"] = batch["img"].to(self.device)
+        batch["cls"] = batch["cls"].to(self.device)
+        return batch
+
+    def progress_string(self):
+        """Returns a formatted string showing training progress."""
+        return ("\n" + "%11s" * (4 + len(self.loss_names))) % (
+            "Epoch",
+            "GPU_mem",
+            *self.loss_names,
+            "Instances",
+            "Size",
+        )
+
+    def get_validator(self):
+        """Returns an instance of ClassificationValidator for validation."""
+        self.loss_names = ["loss"]
+        return yolo.classify.ClassificationValidator(self.test_loader, self.save_dir, _callbacks=self.callbacks)
+
+    def label_loss_items(self, loss_items=None, prefix="train"):
+        """
+        Returns a loss dict with labelled training loss items tensor.
+
+        Not needed for classification but necessary for segmentation & detection
+        """
+        keys = [f"{prefix}/{x}" for x in self.loss_names]
+        if loss_items is None:
+            return keys
+        loss_items = [round(float(loss_items), 5)]
+        return dict(zip(keys, loss_items))
+
+    def plot_metrics(self):
+        """Plots metrics from a CSV file."""
+        plot_results(file=self.csv, classify=True, on_plot=self.on_plot)  # save results.png
+
+    def final_eval(self):
+        """Evaluate trained model and save validation results."""
+        for f in self.last, self.best:
+            if f.exists():
+                strip_optimizer(f)  # strip optimizers
+                if f is self.best:
+                    LOGGER.info(f"\nValidating {f}...")
+                    self.validator.args.data = self.args.data
+                    self.validator.args.plots = self.args.plots
+                    self.metrics = self.validator(model=f)
+                    self.metrics.pop("fitness", None)
+                    self.run_callbacks("on_fit_epoch_end")
+        LOGGER.info(f"Results saved to {colorstr('bold', self.save_dir)}")
+
+    def plot_training_samples(self, batch, ni):
+        """Plots training samples with their annotations."""
+        plot_images(
+            images=batch["img"],
+            batch_idx=torch.arange(len(batch["img"])),
+            cls=batch["cls"].view(-1),  # warning: use .view(), not .squeeze() for Classify models
+            fname=self.save_dir / f"train_batch{ni}.jpg",
+            on_plot=self.on_plot,
+        )

ultralytics/models/yolo/classify/val.py

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+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+import torch
+
+from ultralytics.data import ClassificationDataset, build_dataloader
+from ultralytics.engine.validator import BaseValidator
+from ultralytics.utils import LOGGER
+from ultralytics.utils.metrics import ClassifyMetrics, ConfusionMatrix
+from ultralytics.utils.plotting import plot_images
+
+
+class ClassificationValidator(BaseValidator):
+    """
+    A class extending the BaseValidator class for validation based on a classification model.
+
+    Notes:
+        - Torchvision classification models can also be passed to the 'model' argument, i.e. model='resnet18'.
+
+    Example:
+        ```python
+        from ultralytics.models.yolo.classify import ClassificationValidator
+
+        args = dict(model='yolov8n-cls.pt', data='imagenet10')
+        validator = ClassificationValidator(args=args)
+        validator()
+        ```
+    """
+
+    def __init__(self, dataloader=None, save_dir=None, pbar=None, args=None, _callbacks=None):
+        """Initializes ClassificationValidator instance with args, dataloader, save_dir, and progress bar."""
+        super().__init__(dataloader, save_dir, pbar, args, _callbacks)
+        self.targets = None
+        self.pred = None
+        self.args.task = "classify"
+        self.metrics = ClassifyMetrics()
+
+    def get_desc(self):
+        """Returns a formatted string summarizing classification metrics."""
+        return ("%22s" + "%11s" * 2) % ("classes", "top1_acc", "top5_acc")
+
+    def init_metrics(self, model):
+        """Initialize confusion matrix, class names, and top-1 and top-5 accuracy."""
+        self.names = model.names
+        self.nc = len(model.names)
+        self.confusion_matrix = ConfusionMatrix(nc=self.nc, conf=self.args.conf, task="classify")
+        self.pred = []
+        self.targets = []
+
+    def preprocess(self, batch):
+        """Preprocesses input batch and returns it."""
+        batch["img"] = batch["img"].to(self.device, non_blocking=True)
+        batch["img"] = batch["img"].half() if self.args.half else batch["img"].float()
+        batch["cls"] = batch["cls"].to(self.device)
+        return batch
+
+    def update_metrics(self, preds, batch):
+        """Updates running metrics with model predictions and batch targets."""
+        n5 = min(len(self.names), 5)
+        self.pred.append(preds.argsort(1, descending=True)[:, :n5])
+        self.targets.append(batch["cls"])
+
+    def finalize_metrics(self, *args, **kwargs):
+        """Finalizes metrics of the model such as confusion_matrix and speed."""
+        self.confusion_matrix.process_cls_preds(self.pred, self.targets)
+        if self.args.plots:
+            for normalize in True, False:
+                self.confusion_matrix.plot(
+                    save_dir=self.save_dir, names=self.names.values(), normalize=normalize, on_plot=self.on_plot
+                )
+        self.metrics.speed = self.speed
+        self.metrics.confusion_matrix = self.confusion_matrix
+        self.metrics.save_dir = self.save_dir
+
+    def get_stats(self):
+        """Returns a dictionary of metrics obtained by processing targets and predictions."""
+        self.metrics.process(self.targets, self.pred)
+        return self.metrics.results_dict
+
+    def build_dataset(self, img_path):
+        """Creates and returns a ClassificationDataset instance using given image path and preprocessing parameters."""
+        return ClassificationDataset(root=img_path, args=self.args, augment=False, prefix=self.args.split)
+
+    def get_dataloader(self, dataset_path, batch_size):
+        """Builds and returns a data loader for classification tasks with given parameters."""
+        dataset = self.build_dataset(dataset_path)
+        return build_dataloader(dataset, batch_size, self.args.workers, rank=-1)
+
+    def print_results(self):
+        """Prints evaluation metrics for YOLO object detection model."""
+        pf = "%22s" + "%11.3g" * len(self.metrics.keys)  # print format
+        LOGGER.info(pf % ("all", self.metrics.top1, self.metrics.top5))
+
+    def plot_val_samples(self, batch, ni):
+        """Plot validation image samples."""
+        plot_images(
+            images=batch["img"],
+            batch_idx=torch.arange(len(batch["img"])),
+            cls=batch["cls"].view(-1),  # warning: use .view(), not .squeeze() for Classify models
+            fname=self.save_dir / f"val_batch{ni}_labels.jpg",
+            names=self.names,
+            on_plot=self.on_plot,
+        )
+
+    def plot_predictions(self, batch, preds, ni):
+        """Plots predicted bounding boxes on input images and saves the result."""
+        plot_images(
+            batch["img"],
+            batch_idx=torch.arange(len(batch["img"])),
+            cls=torch.argmax(preds, dim=1),
+            fname=self.save_dir / f"val_batch{ni}_pred.jpg",
+            names=self.names,
+            on_plot=self.on_plot,
+        )  # pred