ImageClassifier

class flash.image.classification.model.ImageClassifier(num_classes=None, labels=None, backbone='resnet18', backbone_kwargs=None, head='linear', pretrained=True, loss_fn=None, optimizer='Adam', lr_scheduler=None, metrics=None, learning_rate=None, multi_label=False, training_strategy='default', training_strategy_kwargs=None)

The ImageClassifier is a Task for classifying images. For more details, see Image Classification. The ImageClassifier also supports multi-label classification with multi_label=True. For more details, see Multi-label Image Classification.

You can register custom backbones to use with the ImageClassifier:

from torch import nn
import torchvision
from flash.image import ImageClassifier

# This is useful to create new backbone and make them accessible from `ImageClassifier`
@ImageClassifier.backbones(name="resnet18")
def fn_resnet(pretrained: bool = True):
    model = torchvision.models.resnet18(pretrained)
    # remove the last two layers & turn it into a Sequential model
    backbone = nn.Sequential(*list(model.children())[:-2])
    num_features = model.fc.in_features
    # backbones need to return the num_features to build the head
    return backbone, num_features

Parameters

• num_classes (Optional[int]) – Number of classes to classify.

• backbone (Union[str, Tuple[Module, int]]) – A string or (model, num_features) tuple to use to compute image features, defaults to "resnet18".

• head (Union[str, function, Module]) – A string from ImageClassifier.available_heads(), an nn.Module, or a function of (num_features, num_classes) which returns an nn.Module to use as the model head.

• pretrained (Union[bool, str]) – A bool or string to specify the pretrained weights of the backbone, defaults to True which loads the default supervised pretrained weights.

• loss_fn (Optional[TypeVar(LOSS_FN_TYPE, Callable, Mapping, Sequence, None)]) – Loss function for training, defaults to torch.nn.functional.cross_entropy().

• optimizer (TypeVar(OPTIMIZER_TYPE, str, Callable, Tuple[str, Dict[str, Any]], None)) – Optimizer to use for training.

• lr_scheduler (Optional[TypeVar(LR_SCHEDULER_TYPE, str, Callable, Tuple[str, Dict[str, Any]], Tuple[str, Dict[str, Any], Dict[str, Any]], None)]) – The LR scheduler to use during training.

• metrics (Optional[TypeVar(METRICS_TYPE, Metric, Mapping, Sequence, None)]) – Metrics to compute for training and evaluation. Can either be an metric from the torchmetrics package, a custom metric inheriting from torchmetrics.Metric, a callable function or a list/dict containing a combination of the aforementioned. In all cases, each metric needs to have the signature metric(preds,target) and return a single scalar tensor. Defaults to torchmetrics.Accuracy.

• learning_rate (Optional[float]) – Learning rate to use for training, defaults to 1e-3.

• multi_label (bool) – Whether the targets are multi-label or not.

• training_strategy (Optional[str]) – string indicating the training strategy. Adjust if you want to use learn2learn for doing meta-learning research

• training_strategy_kwargs (Optional[Dict[str, Any]]) – Additional kwargs for setting the training strategy

classmethod available_finetuning_strategies(cls)

Returns a list containing the keys of the available Finetuning Strategies.

Return type

List[str]

classmethod available_lr_schedulers(cls)

Returns a list containing the keys of the available LR schedulers.

Return type

List[str]

classmethod available_optimizers(cls)

Returns a list containing the keys of the available Optimizers.

Return type

List[str]