init

finetune/mmseg/models/decode_heads/aspp_head.py

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+# Copyright (c) OpenMMLab. All rights reserved.
+import torch
+import torch.nn as nn
+from mmcv.cnn import ConvModule
+
+from mmseg.registry import MODELS
+from ..utils import resize
+from .decode_head import BaseDecodeHead
+
+
+class ASPPModule(nn.ModuleList):
+    """Atrous Spatial Pyramid Pooling (ASPP) Module.
+
+    Args:
+        dilations (tuple[int]): Dilation rate of each layer.
+        in_channels (int): Input channels.
+        channels (int): Channels after modules, before conv_seg.
+        conv_cfg (dict|None): Config of conv layers.
+        norm_cfg (dict|None): Config of norm layers.
+        act_cfg (dict): Config of activation layers.
+    """
+
+    def __init__(self, dilations, in_channels, channels, conv_cfg, norm_cfg,
+                 act_cfg):
+        super().__init__()
+        self.dilations = dilations
+        self.in_channels = in_channels
+        self.channels = channels
+        self.conv_cfg = conv_cfg
+        self.norm_cfg = norm_cfg
+        self.act_cfg = act_cfg
+        for dilation in dilations:
+            self.append(
+                ConvModule(
+                    self.in_channels,
+                    self.channels,
+                    1 if dilation == 1 else 3,
+                    dilation=dilation,
+                    padding=0 if dilation == 1 else dilation,
+                    conv_cfg=self.conv_cfg,
+                    norm_cfg=self.norm_cfg,
+                    act_cfg=self.act_cfg))
+
+    def forward(self, x):
+        """Forward function."""
+        aspp_outs = []
+        for aspp_module in self:
+            aspp_outs.append(aspp_module(x))
+
+        return aspp_outs
+
+
+@MODELS.register_module()
+class ASPPHead(BaseDecodeHead):
+    """Rethinking Atrous Convolution for Semantic Image Segmentation.
+
+    This head is the implementation of `DeepLabV3
+    <https://arxiv.org/abs/1706.05587>`_.
+
+    Args:
+        dilations (tuple[int]): Dilation rates for ASPP module.
+            Default: (1, 6, 12, 18).
+    """
+
+    def __init__(self, dilations=(1, 6, 12, 18), **kwargs):
+        super().__init__(**kwargs)
+        assert isinstance(dilations, (list, tuple))
+        self.dilations = dilations
+        self.image_pool = nn.Sequential(
+            nn.AdaptiveAvgPool2d(1),
+            ConvModule(
+                self.in_channels,
+                self.channels,
+                1,
+                conv_cfg=self.conv_cfg,
+                norm_cfg=self.norm_cfg,
+                act_cfg=self.act_cfg))
+        self.aspp_modules = ASPPModule(
+            dilations,
+            self.in_channels,
+            self.channels,
+            conv_cfg=self.conv_cfg,
+            norm_cfg=self.norm_cfg,
+            act_cfg=self.act_cfg)
+        self.bottleneck = ConvModule(
+            (len(dilations) + 1) * self.channels,
+            self.channels,
+            3,
+            padding=1,
+            conv_cfg=self.conv_cfg,
+            norm_cfg=self.norm_cfg,
+            act_cfg=self.act_cfg)
+
+    def _forward_feature(self, inputs):
+        """Forward function for feature maps before classifying each pixel with
+        ``self.cls_seg`` fc.
+
+        Args:
+            inputs (list[Tensor]): List of multi-level img features.
+
+        Returns:
+            feats (Tensor): A tensor of shape (batch_size, self.channels,
+                H, W) which is feature map for last layer of decoder head.
+        """
+        x = self._transform_inputs(inputs)
+        aspp_outs = [
+            resize(
+                self.image_pool(x),
+                size=x.size()[2:],
+                mode='bilinear',
+                align_corners=self.align_corners)
+        ]
+        aspp_outs.extend(self.aspp_modules(x))
+        aspp_outs = torch.cat(aspp_outs, dim=1)
+        feats = self.bottleneck(aspp_outs)
+        return feats
+
+    def forward(self, inputs):
+        """Forward function."""
+        output = self._forward_feature(inputs)
+        output = self.cls_seg(output)
+        return output