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import torch |
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import torch.nn as nn |
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from mmcv.cnn import ConvModule |
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from mmseg.registry import MODELS |
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from .decode_head import BaseDecodeHead |
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@MODELS.register_module() |
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class FCNHead(BaseDecodeHead): |
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"""Fully Convolution Networks for Semantic Segmentation. |
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This head is implemented of `FCNNet <https://arxiv.org/abs/1411.4038>`_. |
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Args: |
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num_convs (int): Number of convs in the head. Default: 2. |
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kernel_size (int): The kernel size for convs in the head. Default: 3. |
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concat_input (bool): Whether concat the input and output of convs |
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before classification layer. |
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dilation (int): The dilation rate for convs in the head. Default: 1. |
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""" |
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def __init__(self, |
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num_convs=2, |
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kernel_size=3, |
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concat_input=True, |
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dilation=1, |
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**kwargs): |
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assert num_convs >= 0 and dilation > 0 and isinstance(dilation, int) |
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self.num_convs = num_convs |
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self.concat_input = concat_input |
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self.kernel_size = kernel_size |
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super().__init__(**kwargs) |
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if num_convs == 0: |
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assert self.in_channels == self.channels |
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conv_padding = (kernel_size // 2) * dilation |
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convs = [] |
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convs.append( |
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ConvModule( |
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self.in_channels, |
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self.channels, |
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kernel_size=kernel_size, |
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padding=conv_padding, |
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dilation=dilation, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg)) |
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for i in range(num_convs - 1): |
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convs.append( |
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ConvModule( |
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self.channels, |
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self.channels, |
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kernel_size=kernel_size, |
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padding=conv_padding, |
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dilation=dilation, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg)) |
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if num_convs == 0: |
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self.convs = nn.Identity() |
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else: |
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self.convs = nn.Sequential(*convs) |
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if self.concat_input: |
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self.conv_cat = ConvModule( |
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self.in_channels + self.channels, |
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self.channels, |
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kernel_size=kernel_size, |
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padding=kernel_size // 2, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg) |
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def _forward_feature(self, inputs): |
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"""Forward function for feature maps before classifying each pixel with |
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``self.cls_seg`` fc. |
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Args: |
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inputs (list[Tensor]): List of multi-level img features. |
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Returns: |
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feats (Tensor): A tensor of shape (batch_size, self.channels, |
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H, W) which is feature map for last layer of decoder head. |
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""" |
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x = self._transform_inputs(inputs) |
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feats = self.convs(x) |
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if self.concat_input: |
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feats = self.conv_cat(torch.cat([x, feats], dim=1)) |
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return feats |
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def forward(self, inputs): |
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"""Forward function.""" |
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output = self._forward_feature(inputs) |
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output = self.cls_seg(output) |
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return output |
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