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# Copyright (c) OpenMMLab. All rights reserved.
from typing import Tuple
import torch.nn as nn
from mmcv.cnn import ConvModule
from mmengine.model import BaseModule, ModuleList
from torch import Tensor
from mmdet.models.backbones.resnet import Bottleneck
from mmdet.registry import MODELS
from mmdet.utils import ConfigType, MultiConfig, OptConfigType, OptMultiConfig
from .bbox_head import BBoxHead
class BasicResBlock(BaseModule):
"""Basic residual block.
This block is a little different from the block in the ResNet backbone.
The kernel size of conv1 is 1 in this block while 3 in ResNet BasicBlock.
Args:
in_channels (int): Channels of the input feature map.
out_channels (int): Channels of the output feature map.
conv_cfg (:obj:`ConfigDict` or dict, optional): The config dict
for convolution layers.
norm_cfg (:obj:`ConfigDict` or dict): The config dict for
normalization layers.
init_cfg (:obj:`ConfigDict` or dict or list[:obj:`ConfigDict` or \
dict], optional): Initialization config dict. Defaults to None
"""
def __init__(self,
in_channels: int,
out_channels: int,
conv_cfg: OptConfigType = None,
norm_cfg: ConfigType = dict(type='BN'),
init_cfg: OptMultiConfig = None) -> None:
super().__init__(init_cfg=init_cfg)
# main path
self.conv1 = ConvModule(
in_channels,
in_channels,
kernel_size=3,
padding=1,
bias=False,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg)
self.conv2 = ConvModule(
in_channels,
out_channels,
kernel_size=1,
bias=False,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg,
act_cfg=None)
# identity path
self.conv_identity = ConvModule(
in_channels,
out_channels,
kernel_size=1,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg,
act_cfg=None)
self.relu = nn.ReLU(inplace=True)
def forward(self, x: Tensor) -> Tensor:
"""Forward function."""
identity = x
x = self.conv1(x)
x = self.conv2(x)
identity = self.conv_identity(identity)
out = x + identity
out = self.relu(out)
return out
@MODELS.register_module()
class DoubleConvFCBBoxHead(BBoxHead):
r"""Bbox head used in Double-Head R-CNN
.. code-block:: none
/-> cls
/-> shared convs ->
\-> reg
roi features
/-> cls
\-> shared fc ->
\-> reg
""" # noqa: W605
def __init__(self,
num_convs: int = 0,
num_fcs: int = 0,
conv_out_channels: int = 1024,
fc_out_channels: int = 1024,
conv_cfg: OptConfigType = None,
norm_cfg: ConfigType = dict(type='BN'),
init_cfg: MultiConfig = dict(
type='Normal',
override=[
dict(type='Normal', name='fc_cls', std=0.01),
dict(type='Normal', name='fc_reg', std=0.001),
dict(
type='Xavier',
name='fc_branch',
distribution='uniform')
]),
**kwargs) -> None:
kwargs.setdefault('with_avg_pool', True)
super().__init__(init_cfg=init_cfg, **kwargs)
assert self.with_avg_pool
assert num_convs > 0
assert num_fcs > 0
self.num_convs = num_convs
self.num_fcs = num_fcs
self.conv_out_channels = conv_out_channels
self.fc_out_channels = fc_out_channels
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
# increase the channel of input features
self.res_block = BasicResBlock(self.in_channels,
self.conv_out_channels)
# add conv heads
self.conv_branch = self._add_conv_branch()
# add fc heads
self.fc_branch = self._add_fc_branch()
out_dim_reg = 4 if self.reg_class_agnostic else 4 * self.num_classes
self.fc_reg = nn.Linear(self.conv_out_channels, out_dim_reg)
self.fc_cls = nn.Linear(self.fc_out_channels, self.num_classes + 1)
self.relu = nn.ReLU()
def _add_conv_branch(self) -> None:
"""Add the fc branch which consists of a sequential of conv layers."""
branch_convs = ModuleList()
for i in range(self.num_convs):
branch_convs.append(
Bottleneck(
inplanes=self.conv_out_channels,
planes=self.conv_out_channels // 4,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg))
return branch_convs
def _add_fc_branch(self) -> None:
"""Add the fc branch which consists of a sequential of fc layers."""
branch_fcs = ModuleList()
for i in range(self.num_fcs):
fc_in_channels = (
self.in_channels *
self.roi_feat_area if i == 0 else self.fc_out_channels)
branch_fcs.append(nn.Linear(fc_in_channels, self.fc_out_channels))
return branch_fcs
def forward(self, x_cls: Tensor, x_reg: Tensor) -> Tuple[Tensor]:
"""Forward features from the upstream network.
Args:
x_cls (Tensor): Classification features of rois
x_reg (Tensor): Regression features from the upstream network.
Returns:
tuple: A tuple of classification scores and bbox prediction.
- cls_score (Tensor): Classification score predictions of rois.
each roi predicts num_classes + 1 channels.
- bbox_pred (Tensor): BBox deltas predictions of rois. each roi
predicts 4 * num_classes channels.
"""
# conv head
x_conv = self.res_block(x_reg)
for conv in self.conv_branch:
x_conv = conv(x_conv)
if self.with_avg_pool:
x_conv = self.avg_pool(x_conv)
x_conv = x_conv.view(x_conv.size(0), -1)
bbox_pred = self.fc_reg(x_conv)
# fc head
x_fc = x_cls.view(x_cls.size(0), -1)
for fc in self.fc_branch:
x_fc = self.relu(fc(x_fc))
cls_score = self.fc_cls(x_fc)
return cls_score, bbox_pred