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import torch
import torch.nn as nn
from mmcv.cnn import ConvModule, normal_init
from mmseg.ops import resize
class BaseDecodeHead(nn.Module):
"""Base class for BaseDecodeHead.
Args:
in_channels (int|Sequence[int]): Input channels.
channels (int): Channels after modules, before conv_seg.
num_classes (int): Number of classes.
dropout_ratio (float): Ratio of dropout layer. Default: 0.1.
conv_cfg (dict|None): Config of conv layers. Default: None.
norm_cfg (dict|None): Config of norm layers. Default: None.
act_cfg (dict): Config of activation layers.
Default: dict(type='ReLU')
in_index (int|Sequence[int]): Input feature index. Default: -1
input_transform (str|None): Transformation type of input features.
Options: 'resize_concat', 'multiple_select', None.
'resize_concat': Multiple feature maps will be resize to the
same size as first one and than concat together.
Usually used in FCN head of HRNet.
'multiple_select': Multiple feature maps will be bundle into
a list and passed into decode head.
None: Only one select feature map is allowed.
Default: None.
loss_decode (dict): Config of decode loss.
Default: dict(type='CrossEntropyLoss').
ignore_index (int | None): The label index to be ignored. When using
masked BCE loss, ignore_index should be set to None. Default: 255
sampler (dict|None): The config of segmentation map sampler.
Default: None.
align_corners (bool): align_corners argument of F.interpolate.
Default: False.
"""
def __init__(self,
in_channels,
channels,
*,
num_classes,
dropout_ratio=0.1,
conv_cfg=None,
norm_cfg=dict(type='BN'),
act_cfg=dict(type='ReLU'),
in_index=-1,
input_transform=None,
ignore_index=255,
align_corners=False):
super(BaseDecodeHead, self).__init__()
self._init_inputs(in_channels, in_index, input_transform)
self.channels = channels
self.num_classes = num_classes
self.dropout_ratio = dropout_ratio
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
self.act_cfg = act_cfg
self.in_index = in_index
self.ignore_index = ignore_index
self.align_corners = align_corners
self.conv_seg = nn.Conv2d(channels, num_classes, kernel_size=1)
if dropout_ratio > 0:
self.dropout = nn.Dropout2d(dropout_ratio)
else:
self.dropout = None
def extra_repr(self):
"""Extra repr."""
s = f'input_transform={self.input_transform}, ' \
f'ignore_index={self.ignore_index}, ' \
f'align_corners={self.align_corners}'
return s
def _init_inputs(self, in_channels, in_index, input_transform):
"""Check and initialize input transforms.
The in_channels, in_index and input_transform must match.
Specifically, when input_transform is None, only single feature map
will be selected. So in_channels and in_index must be of type int.
When input_transform
Args:
in_channels (int|Sequence[int]): Input channels.
in_index (int|Sequence[int]): Input feature index.
input_transform (str|None): Transformation type of input features.
Options: 'resize_concat', 'multiple_select', None.
'resize_concat': Multiple feature maps will be resize to the
same size as first one and than concat together.
Usually used in FCN head of HRNet.
'multiple_select': Multiple feature maps will be bundle into
a list and passed into decode head.
None: Only one select feature map is allowed.
"""
if input_transform is not None:
assert input_transform in ['resize_concat', 'multiple_select']
self.input_transform = input_transform
self.in_index = in_index
if input_transform is not None:
assert isinstance(in_channels, (list, tuple))
assert isinstance(in_index, (list, tuple))
assert len(in_channels) == len(in_index)
if input_transform == 'resize_concat':
self.in_channels = sum(in_channels)
else:
self.in_channels = in_channels
else:
assert isinstance(in_channels, int)
assert isinstance(in_index, int)
self.in_channels = in_channels
def init_weights(self):
"""Initialize weights of classification layer."""
normal_init(self.conv_seg, mean=0, std=0.01)
def _transform_inputs(self, inputs):
"""Transform inputs for decoder.
Args:
inputs (list[Tensor]): List of multi-level img features.
Returns:
Tensor: The transformed inputs
"""
if self.input_transform == 'resize_concat':
inputs = [inputs[i] for i in self.in_index]
upsampled_inputs = [
resize(
input=x,
size=inputs[0].shape[2:],
mode='bilinear',
align_corners=self.align_corners) for x in inputs
]
inputs = torch.cat(upsampled_inputs, dim=1)
elif self.input_transform == 'multiple_select':
inputs = [inputs[i] for i in self.in_index]
else:
inputs = inputs[self.in_index]
return inputs
def forward(self, inputs):
"""Placeholder of forward function."""
pass
def cls_seg(self, feat):
"""Classify each pixel."""
if self.dropout is not None:
feat = self.dropout(feat)
output = self.conv_seg(feat)
return output
class FCNHead(BaseDecodeHead):
"""Fully Convolution Networks for Semantic Segmentation.
This head is implemented of `FCNNet <https://arxiv.org/abs/1411.4038>`_.
Args:
num_convs (int): Number of convs in the head. Default: 2.
kernel_size (int): The kernel size for convs in the head. Default: 3.
concat_input (bool): Whether concat the input and output of convs
before classification layer.
"""
def __init__(self,
num_convs=2,
kernel_size=3,
concat_input=True,
**kwargs):
assert num_convs >= 0
self.num_convs = num_convs
self.concat_input = concat_input
self.kernel_size = kernel_size
super(FCNHead, self).__init__(**kwargs)
if num_convs == 0:
assert self.in_channels == self.channels
convs = []
convs.append(
ConvModule(
self.in_channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg))
for i in range(num_convs - 1):
convs.append(
ConvModule(
self.channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg))
if num_convs == 0:
self.convs = nn.Identity()
else:
self.convs = nn.Sequential(*convs)
if self.concat_input:
self.conv_cat = ConvModule(
self.in_channels + self.channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg)
def forward(self, inputs):
"""Forward function."""
x = self._transform_inputs(inputs)
output = self.convs(x)
if self.concat_input:
output = self.conv_cat(torch.cat([x, output], dim=1))
output = self.cls_seg(output)
return output
class MultiHeadFCNHead(nn.Module):
"""Fully Convolution Networks for Semantic Segmentation.
This head is implemented of `FCNNet <https://arxiv.org/abs/1411.4038>`_.
Args:
num_convs (int): Number of convs in the head. Default: 2.
kernel_size (int): The kernel size for convs in the head. Default: 3.
concat_input (bool): Whether concat the input and output of convs
before classification layer.
"""
def __init__(self,
in_channels,
channels,
*,
num_classes,
dropout_ratio=0.1,
conv_cfg=None,
norm_cfg=dict(type='BN'),
act_cfg=dict(type='ReLU'),
in_index=-1,
input_transform=None,
ignore_index=255,
align_corners=False,
num_convs=2,
kernel_size=3,
concat_input=True,
num_head=18,
**kwargs):
super(MultiHeadFCNHead, self).__init__()
assert num_convs >= 0
self.num_convs = num_convs
self.concat_input = concat_input
self.kernel_size = kernel_size
self._init_inputs(in_channels, in_index, input_transform)
self.channels = channels
self.num_classes = num_classes
self.dropout_ratio = dropout_ratio
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
self.act_cfg = act_cfg
self.in_index = in_index
self.num_head = num_head
self.ignore_index = ignore_index
self.align_corners = align_corners
if dropout_ratio > 0:
self.dropout = nn.Dropout2d(dropout_ratio)
conv_seg_head_list = []
for _ in range(self.num_head):
conv_seg_head_list.append(
nn.Conv2d(channels, num_classes, kernel_size=1))
self.conv_seg_head_list = nn.ModuleList(conv_seg_head_list)
self.init_weights()
if num_convs == 0:
assert self.in_channels == self.channels
convs_list = []
conv_cat_list = []
for _ in range(self.num_head):
convs = []
convs.append(
ConvModule(
self.in_channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg))
for _ in range(num_convs - 1):
convs.append(
ConvModule(
self.channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg))
if num_convs == 0:
convs_list.append(nn.Identity())
else:
convs_list.append(nn.Sequential(*convs))
if self.concat_input:
conv_cat_list.append(
ConvModule(
self.in_channels + self.channels,
self.channels,
kernel_size=kernel_size,
padding=kernel_size // 2,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
act_cfg=self.act_cfg))
self.convs_list = nn.ModuleList(convs_list)
self.conv_cat_list = nn.ModuleList(conv_cat_list)
def forward(self, inputs):
"""Forward function."""
x = self._transform_inputs(inputs)
output_list = []
for head_idx in range(self.num_head):
output = self.convs_list[head_idx](x)
if self.concat_input:
output = self.conv_cat_list[head_idx](
torch.cat([x, output], dim=1))
if self.dropout is not None:
output = self.dropout(output)
output = self.conv_seg_head_list[head_idx](output)
output_list.append(output)
return output_list
def _init_inputs(self, in_channels, in_index, input_transform):
"""Check and initialize input transforms.
The in_channels, in_index and input_transform must match.
Specifically, when input_transform is None, only single feature map
will be selected. So in_channels and in_index must be of type int.
When input_transform
Args:
in_channels (int|Sequence[int]): Input channels.
in_index (int|Sequence[int]): Input feature index.
input_transform (str|None): Transformation type of input features.
Options: 'resize_concat', 'multiple_select', None.
'resize_concat': Multiple feature maps will be resize to the
same size as first one and than concat together.
Usually used in FCN head of HRNet.
'multiple_select': Multiple feature maps will be bundle into
a list and passed into decode head.
None: Only one select feature map is allowed.
"""
if input_transform is not None:
assert input_transform in ['resize_concat', 'multiple_select']
self.input_transform = input_transform
self.in_index = in_index
if input_transform is not None:
assert isinstance(in_channels, (list, tuple))
assert isinstance(in_index, (list, tuple))
assert len(in_channels) == len(in_index)
if input_transform == 'resize_concat':
self.in_channels = sum(in_channels)
else:
self.in_channels = in_channels
else:
assert isinstance(in_channels, int)
assert isinstance(in_index, int)
self.in_channels = in_channels
def init_weights(self):
"""Initialize weights of classification layer."""
for conv_seg_head in self.conv_seg_head_list:
normal_init(conv_seg_head, mean=0, std=0.01)
def _transform_inputs(self, inputs):
"""Transform inputs for decoder.
Args:
inputs (list[Tensor]): List of multi-level img features.
Returns:
Tensor: The transformed inputs
"""
if self.input_transform == 'resize_concat':
inputs = [inputs[i] for i in self.in_index]
upsampled_inputs = [
resize(
input=x,
size=inputs[0].shape[2:],
mode='bilinear',
align_corners=self.align_corners) for x in inputs
]
inputs = torch.cat(upsampled_inputs, dim=1)
elif self.input_transform == 'multiple_select':
inputs = [inputs[i] for i in self.in_index]
else:
inputs = inputs[self.in_index]
return inputs