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- # Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
- #
- # Licensed under the Apache License, Version 2.0 (the "License");
- # you may not use this file except in compliance with the License.
- # You may obtain a copy of the License at
- #
- # http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- # See the License for the specific language governing permissions and
- # limitations under the License.
- import paddle
- import paddle.nn as nn
- import paddle.nn.functional as F
- from paddlex.paddleseg import utils
- from paddlex.paddleseg.cvlibs import manager, param_init
- from paddlex.paddleseg.models import layers
- @manager.MODELS.add_component
- class OCRNet(nn.Layer):
- """
- The OCRNet implementation based on PaddlePaddle.
- The original article refers to
- Yuan, Yuhui, et al. "Object-Contextual Representations for Semantic Segmentation"
- (https://arxiv.org/pdf/1909.11065.pdf)
- Args:
- num_classes (int): The unique number of target classes.
- backbone (Paddle.nn.Layer): Backbone network.
- backbone_indices (tuple): A tuple indicates the indices of output of backbone.
- It can be either one or two values, if two values, the first index will be taken as
- a deep-supervision feature in auxiliary layer; the second one will be taken as
- input of pixel representation. If one value, it is taken by both above.
- ocr_mid_channels (int, optional): The number of middle channels in OCRHead. Default: 512.
- ocr_key_channels (int, optional): The number of key channels in ObjectAttentionBlock. Default: 256.
- align_corners (bool): An argument of F.interpolate. It should be set to False when the output size of feature
- is even, e.g. 1024x512, otherwise it is True, e.g. 769x769. Default: False.
- pretrained (str, optional): The path or url of pretrained model. Default: None.
- """
- def __init__(self,
- num_classes,
- backbone,
- backbone_indices,
- ocr_mid_channels=512,
- ocr_key_channels=256,
- align_corners=False,
- pretrained=None):
- super().__init__()
- self.backbone = backbone
- self.backbone_indices = backbone_indices
- in_channels = [
- self.backbone.feat_channels[i] for i in backbone_indices
- ]
- self.head = OCRHead(
- num_classes=num_classes,
- in_channels=in_channels,
- ocr_mid_channels=ocr_mid_channels,
- ocr_key_channels=ocr_key_channels)
- self.align_corners = align_corners
- self.pretrained = pretrained
- self.init_weight()
- def forward(self, x):
- feats = self.backbone(x)
- feats = [feats[i] for i in self.backbone_indices]
- logit_list = self.head(feats)
- if not self.training:
- logit_list = [logit_list[0]]
- logit_list = [
- F.interpolate(
- logit,
- paddle.shape(x)[2:],
- mode='bilinear',
- align_corners=self.align_corners) for logit in logit_list
- ]
- return logit_list
- def init_weight(self):
- if self.pretrained is not None:
- utils.load_entire_model(self, self.pretrained)
- class OCRHead(nn.Layer):
- """
- The Object contextual representation head.
- Args:
- num_classes(int): The unique number of target classes.
- in_channels(tuple): The number of input channels.
- ocr_mid_channels(int, optional): The number of middle channels in OCRHead. Default: 512.
- ocr_key_channels(int, optional): The number of key channels in ObjectAttentionBlock. Default: 256.
- """
- def __init__(self,
- num_classes,
- in_channels,
- ocr_mid_channels=512,
- ocr_key_channels=256):
- super().__init__()
- self.num_classes = num_classes
- self.spatial_gather = SpatialGatherBlock(ocr_mid_channels, num_classes)
- self.spatial_ocr = SpatialOCRModule(ocr_mid_channels, ocr_key_channels,
- ocr_mid_channels)
- self.indices = [-2, -1] if len(in_channels) > 1 else [-1, -1]
- self.conv3x3_ocr = layers.ConvBNReLU(
- in_channels[self.indices[1]], ocr_mid_channels, 3, padding=1)
- self.cls_head = nn.Conv2D(ocr_mid_channels, self.num_classes, 1)
- self.aux_head = nn.Sequential(
- layers.ConvBNReLU(in_channels[self.indices[0]],
- in_channels[self.indices[0]], 1),
- nn.Conv2D(in_channels[self.indices[0]], self.num_classes, 1))
- self.init_weight()
- def forward(self, feat_list):
- feat_shallow, feat_deep = feat_list[self.indices[0]], feat_list[
- self.indices[1]]
- soft_regions = self.aux_head(feat_shallow)
- pixels = self.conv3x3_ocr(feat_deep)
- object_regions = self.spatial_gather(pixels, soft_regions)
- ocr = self.spatial_ocr(pixels, object_regions)
- logit = self.cls_head(ocr)
- return [logit, soft_regions]
- def init_weight(self):
- """Initialize the parameters of model parts."""
- for sublayer in self.sublayers():
- if isinstance(sublayer, nn.Conv2D):
- param_init.normal_init(sublayer.weight, std=0.001)
- elif isinstance(sublayer, (nn.BatchNorm, nn.SyncBatchNorm)):
- param_init.constant_init(sublayer.weight, value=1.0)
- param_init.constant_init(sublayer.bias, value=0.0)
- class SpatialGatherBlock(nn.Layer):
- """Aggregation layer to compute the pixel-region representation."""
- def __init__(self, pixels_channels, regions_channels):
- super().__init__()
- self.pixels_channels = pixels_channels
- self.regions_channels = regions_channels
- def forward(self, pixels, regions):
- # pixels: from (n, c, h, w) to (n, h*w, c)
- pixels = paddle.reshape(pixels, (0, self.pixels_channels, -1))
- pixels = paddle.transpose(pixels, (0, 2, 1))
- # regions: from (n, k, h, w) to (n, k, h*w)
- regions = paddle.reshape(regions, (0, self.regions_channels, -1))
- regions = F.softmax(regions, axis=2)
- # feats: from (n, k, c) to (n, c, k, 1)
- feats = paddle.bmm(regions, pixels)
- feats = paddle.transpose(feats, (0, 2, 1))
- feats = paddle.unsqueeze(feats, axis=-1)
- return feats
- class SpatialOCRModule(nn.Layer):
- """Aggregate the global object representation to update the representation for each pixel."""
- def __init__(self,
- in_channels,
- key_channels,
- out_channels,
- dropout_rate=0.1):
- super().__init__()
- self.attention_block = ObjectAttentionBlock(in_channels, key_channels)
- self.conv1x1 = nn.Sequential(
- layers.ConvBNReLU(2 * in_channels, out_channels, 1),
- nn.Dropout2D(dropout_rate))
- def forward(self, pixels, regions):
- context = self.attention_block(pixels, regions)
- feats = paddle.concat([context, pixels], axis=1)
- feats = self.conv1x1(feats)
- return feats
- class ObjectAttentionBlock(nn.Layer):
- """A self-attention module."""
- def __init__(self, in_channels, key_channels):
- super().__init__()
- self.in_channels = in_channels
- self.key_channels = key_channels
- self.f_pixel = nn.Sequential(
- layers.ConvBNReLU(in_channels, key_channels, 1),
- layers.ConvBNReLU(key_channels, key_channels, 1))
- self.f_object = nn.Sequential(
- layers.ConvBNReLU(in_channels, key_channels, 1),
- layers.ConvBNReLU(key_channels, key_channels, 1))
- self.f_down = layers.ConvBNReLU(in_channels, key_channels, 1)
- self.f_up = layers.ConvBNReLU(key_channels, in_channels, 1)
- def forward(self, x, proxy):
- x_shape = paddle.shape(x)
- # query : from (n, c1, h1, w1) to (n, h1*w1, key_channels)
- query = self.f_pixel(x)
- query = paddle.reshape(query, (0, self.key_channels, -1))
- query = paddle.transpose(query, (0, 2, 1))
- # key : from (n, c2, h2, w2) to (n, key_channels, h2*w2)
- key = self.f_object(proxy)
- key = paddle.reshape(key, (0, self.key_channels, -1))
- # value : from (n, c2, h2, w2) to (n, h2*w2, key_channels)
- value = self.f_down(proxy)
- value = paddle.reshape(value, (0, self.key_channels, -1))
- value = paddle.transpose(value, (0, 2, 1))
- # sim_map (n, h1*w1, h2*w2)
- sim_map = paddle.bmm(query, key)
- sim_map = (self.key_channels**-.5) * sim_map
- sim_map = F.softmax(sim_map, axis=-1)
- # context from (n, h1*w1, key_channels) to (n , out_channels, h1, w1)
- context = paddle.bmm(sim_map, value)
- context = paddle.transpose(context, (0, 2, 1))
- context = paddle.reshape(
- context, (0, self.key_channels, x_shape[2], x_shape[3]))
- context = self.f_up(context)
- return context
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