torchvision.models.detection.fasterrcnn_resnet50_fpn_v2(*, weights: Optional[torchvision.models.detection.faster_rcnn.FasterRCNN_ResNet50_FPN_V2_Weights] = None, progress: bool = True, num_classes: Optional[int] = None, weights_backbone: Optional[torchvision.models.resnet.ResNet50_Weights] = None, trainable_backbone_layers: Optional[int] = None, **kwargs: Any)torchvision.models.detection.faster_rcnn.FasterRCNN[source]

Constructs an improved Faster R-CNN model with a ResNet-50-FPN backbone from Benchmarking Detection Transfer Learning with Vision Transformers paper.


The detection module is in Beta stage, and backward compatibility is not guaranteed.

It works similarly to Faster R-CNN with ResNet-50 FPN backbone. See fasterrcnn_resnet50_fpn() for more details.

  • weights (FasterRCNN_ResNet50_FPN_V2_Weights, optional) – The pretrained weights to use. See FasterRCNN_ResNet50_FPN_V2_Weights below for more details, and possible values. By default, no pre-trained weights are used.

  • progress (bool, optional) – If True, displays a progress bar of the download to stderr. Default is True.

  • num_classes (int, optional) – number of output classes of the model (including the background)

  • weights_backbone (ResNet50_Weights, optional) – The pretrained weights for the backbone.

  • trainable_backbone_layers (int, optional) – number of trainable (not frozen) layers starting from final block. Valid values are between 0 and 5, with 5 meaning all backbone layers are trainable. If None is passed (the default) this value is set to 3.

  • **kwargs – parameters passed to the torchvision.models.detection.faster_rcnn.FasterRCNN base class. Please refer to the source code for more details about this class.

class torchvision.models.detection.FasterRCNN_ResNet50_FPN_V2_Weights(value)[source]

The model builder above accepts the following values as the weights parameter. FasterRCNN_ResNet50_FPN_V2_Weights.DEFAULT is equivalent to FasterRCNN_ResNet50_FPN_V2_Weights.COCO_V1. You can also use strings, e.g. weights='DEFAULT' or weights='COCO_V1'.


These weights were produced using an enhanced training recipe to boost the model accuracy. Also available as FasterRCNN_ResNet50_FPN_V2_Weights.DEFAULT.

box_map (on COCO-val2017)



__background__, person, bicycle, … (88 omitted)


height=1, width=1





The inference transforms are available at FasterRCNN_ResNet50_FPN_V2_Weights.COCO_V1.transforms and perform the following preprocessing operations: Accepts PIL.Image, batched (B, C, H, W) and single (C, H, W) image torch.Tensor objects. The images are rescaled to [0.0, 1.0].


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