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| # Copyright (c) OpenMMLab. All rights reserved. | |
| import torch | |
| import torch.nn as nn | |
| import torch.nn.functional as F | |
| from mmcv.cnn import ConvModule | |
| from mmseg.registry import MODELS | |
| from ..utils import resize | |
| from .decode_head import BaseDecodeHead | |
| class ACM(nn.Module): | |
| """Adaptive Context Module used in APCNet. | |
| Args: | |
| pool_scale (int): Pooling scale used in Adaptive Context | |
| Module to extract region features. | |
| fusion (bool): Add one conv to fuse residual feature. | |
| 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, pool_scale, fusion, in_channels, channels, conv_cfg, | |
| norm_cfg, act_cfg): | |
| super().__init__() | |
| self.pool_scale = pool_scale | |
| self.fusion = fusion | |
| self.in_channels = in_channels | |
| self.channels = channels | |
| self.conv_cfg = conv_cfg | |
| self.norm_cfg = norm_cfg | |
| self.act_cfg = act_cfg | |
| self.pooled_redu_conv = ConvModule( | |
| self.in_channels, | |
| self.channels, | |
| 1, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg) | |
| self.input_redu_conv = ConvModule( | |
| self.in_channels, | |
| self.channels, | |
| 1, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg) | |
| self.global_info = ConvModule( | |
| self.channels, | |
| self.channels, | |
| 1, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg) | |
| self.gla = nn.Conv2d(self.channels, self.pool_scale**2, 1, 1, 0) | |
| self.residual_conv = ConvModule( | |
| self.channels, | |
| self.channels, | |
| 1, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg) | |
| if self.fusion: | |
| self.fusion_conv = ConvModule( | |
| self.channels, | |
| self.channels, | |
| 1, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg) | |
| def forward(self, x): | |
| """Forward function.""" | |
| pooled_x = F.adaptive_avg_pool2d(x, self.pool_scale) | |
| # [batch_size, channels, h, w] | |
| x = self.input_redu_conv(x) | |
| # [batch_size, channels, pool_scale, pool_scale] | |
| pooled_x = self.pooled_redu_conv(pooled_x) | |
| batch_size = x.size(0) | |
| # [batch_size, pool_scale * pool_scale, channels] | |
| pooled_x = pooled_x.view(batch_size, self.channels, | |
| -1).permute(0, 2, 1).contiguous() | |
| # [batch_size, h * w, pool_scale * pool_scale] | |
| affinity_matrix = self.gla(x + resize( | |
| self.global_info(F.adaptive_avg_pool2d(x, 1)), size=x.shape[2:]) | |
| ).permute(0, 2, 3, 1).reshape( | |
| batch_size, -1, self.pool_scale**2) | |
| affinity_matrix = F.sigmoid(affinity_matrix) | |
| # [batch_size, h * w, channels] | |
| z_out = torch.matmul(affinity_matrix, pooled_x) | |
| # [batch_size, channels, h * w] | |
| z_out = z_out.permute(0, 2, 1).contiguous() | |
| # [batch_size, channels, h, w] | |
| z_out = z_out.view(batch_size, self.channels, x.size(2), x.size(3)) | |
| z_out = self.residual_conv(z_out) | |
| z_out = F.relu(z_out + x) | |
| if self.fusion: | |
| z_out = self.fusion_conv(z_out) | |
| return z_out | |
| class APCHead(BaseDecodeHead): | |
| """Adaptive Pyramid Context Network for Semantic Segmentation. | |
| This head is the implementation of | |
| `APCNet <https://openaccess.thecvf.com/content_CVPR_2019/papers/\ | |
| He_Adaptive_Pyramid_Context_Network_for_Semantic_Segmentation_\ | |
| CVPR_2019_paper.pdf>`_. | |
| Args: | |
| pool_scales (tuple[int]): Pooling scales used in Adaptive Context | |
| Module. Default: (1, 2, 3, 6). | |
| fusion (bool): Add one conv to fuse residual feature. | |
| """ | |
| def __init__(self, pool_scales=(1, 2, 3, 6), fusion=True, **kwargs): | |
| super().__init__(**kwargs) | |
| assert isinstance(pool_scales, (list, tuple)) | |
| self.pool_scales = pool_scales | |
| self.fusion = fusion | |
| acm_modules = [] | |
| for pool_scale in self.pool_scales: | |
| acm_modules.append( | |
| ACM(pool_scale, | |
| self.fusion, | |
| self.in_channels, | |
| self.channels, | |
| conv_cfg=self.conv_cfg, | |
| norm_cfg=self.norm_cfg, | |
| act_cfg=self.act_cfg)) | |
| self.acm_modules = nn.ModuleList(acm_modules) | |
| self.bottleneck = ConvModule( | |
| self.in_channels + len(pool_scales) * self.channels, | |
| self.channels, | |
| 3, | |
| padding=1, | |
| 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) | |
| acm_outs = [x] | |
| for acm_module in self.acm_modules: | |
| acm_outs.append(acm_module(x)) | |
| acm_outs = torch.cat(acm_outs, dim=1) | |
| output = self.bottleneck(acm_outs) | |
| output = self.cls_seg(output) | |
| return output | |