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22e1f7f | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | import torch
import torch.nn as nn
from torchvision.models import resnet50, ResNet50_Weights
from torchvision.models._utils import IntermediateLayerGetter
from torchvision.ops import FeaturePyramidNetwork
from torchvision.ops.feature_pyramid_network import LastLevelMaxPool
class ResNet50FPNBackbone(nn.Module):
def __init__(self, pretrained=True, out_channels=256):
super().__init__()
weights = ResNet50_Weights.DEFAULT if pretrained else None
resnet = resnet50(weights=weights)
self.body = IntermediateLayerGetter(
resnet,
return_layers={
"layer1": "c2",
"layer2": "c3",
"layer3": "c4",
"layer4": "c5"
}
)
self.fpn = FeaturePyramidNetwork(
in_channels_list=[
256,
512,
1024,
2048
],
out_channels=out_channels,
extra_blocks=LastLevelMaxPool()
)
self.out_channels = out_channels
def forward(self, x):
features = self.body(x)
features = self.fpn(features)
return features |