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# copyright (c) 2022 PaddlePaddle Authors. All Rights Reserve. | |
# | |
# 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. | |
""" | |
This code is refer from: | |
https://github.com/hikopensource/DAVAR-Lab-OCR/davarocr/davar_rcg/models/backbones/ResNet32.py | |
""" | |
from __future__ import absolute_import | |
from __future__ import division | |
from __future__ import print_function | |
import paddle.nn as nn | |
__all__ = ["ResNet32"] | |
conv_weight_attr = nn.initializer.KaimingNormal() | |
class ResNet32(nn.Layer): | |
""" | |
Feature Extractor is proposed in FAN Ref [1] | |
Ref [1]: Focusing Attention: Towards Accurate Text Recognition in Neural Images ICCV-2017 | |
""" | |
def __init__(self, in_channels, out_channels=512): | |
""" | |
Args: | |
in_channels (int): input channel | |
output_channel (int): output channel | |
""" | |
super(ResNet32, self).__init__() | |
self.out_channels = out_channels | |
self.ConvNet = ResNet(in_channels, out_channels, BasicBlock, [1, 2, 5, 3]) | |
def forward(self, inputs): | |
""" | |
Args: | |
inputs: input feature | |
Returns: | |
output feature | |
""" | |
return self.ConvNet(inputs) | |
class BasicBlock(nn.Layer): | |
"""Res-net Basic Block""" | |
expansion = 1 | |
def __init__(self, inplanes, planes, | |
stride=1, downsample=None, | |
norm_type='BN', **kwargs): | |
""" | |
Args: | |
inplanes (int): input channel | |
planes (int): channels of the middle feature | |
stride (int): stride of the convolution | |
downsample (int): type of the down_sample | |
norm_type (str): type of the normalization | |
**kwargs (None): backup parameter | |
""" | |
super(BasicBlock, self).__init__() | |
self.conv1 = self._conv3x3(inplanes, planes) | |
self.bn1 = nn.BatchNorm2D(planes) | |
self.conv2 = self._conv3x3(planes, planes) | |
self.bn2 = nn.BatchNorm2D(planes) | |
self.relu = nn.ReLU() | |
self.downsample = downsample | |
self.stride = stride | |
def _conv3x3(self, in_planes, out_planes, stride=1): | |
""" | |
Args: | |
in_planes (int): input channel | |
out_planes (int): channels of the middle feature | |
stride (int): stride of the convolution | |
Returns: | |
nn.Layer: Conv2D with kernel = 3 | |
""" | |
return nn.Conv2D(in_planes, out_planes, | |
kernel_size=3, stride=stride, | |
padding=1, weight_attr=conv_weight_attr, | |
bias_attr=False) | |
def forward(self, x): | |
residual = x | |
out = self.conv1(x) | |
out = self.bn1(out) | |
out = self.relu(out) | |
out = self.conv2(out) | |
out = self.bn2(out) | |
if self.downsample is not None: | |
residual = self.downsample(x) | |
out += residual | |
out = self.relu(out) | |
return out | |
class ResNet(nn.Layer): | |
"""Res-Net network structure""" | |
def __init__(self, input_channel, | |
output_channel, block, layers): | |
""" | |
Args: | |
input_channel (int): input channel | |
output_channel (int): output channel | |
block (BasicBlock): convolution block | |
layers (list): layers of the block | |
""" | |
super(ResNet, self).__init__() | |
self.output_channel_block = [int(output_channel / 4), | |
int(output_channel / 2), | |
output_channel, | |
output_channel] | |
self.inplanes = int(output_channel / 8) | |
self.conv0_1 = nn.Conv2D(input_channel, int(output_channel / 16), | |
kernel_size=3, stride=1, | |
padding=1, | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn0_1 = nn.BatchNorm2D(int(output_channel / 16)) | |
self.conv0_2 = nn.Conv2D(int(output_channel / 16), self.inplanes, | |
kernel_size=3, stride=1, | |
padding=1, | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn0_2 = nn.BatchNorm2D(self.inplanes) | |
self.relu = nn.ReLU() | |
self.maxpool1 = nn.MaxPool2D(kernel_size=2, stride=2, padding=0) | |
self.layer1 = self._make_layer(block, | |
self.output_channel_block[0], | |
layers[0]) | |
self.conv1 = nn.Conv2D(self.output_channel_block[0], | |
self.output_channel_block[0], | |
kernel_size=3, stride=1, | |
padding=1, | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn1 = nn.BatchNorm2D(self.output_channel_block[0]) | |
self.maxpool2 = nn.MaxPool2D(kernel_size=2, stride=2, padding=0) | |
self.layer2 = self._make_layer(block, | |
self.output_channel_block[1], | |
layers[1], stride=1) | |
self.conv2 = nn.Conv2D(self.output_channel_block[1], | |
self.output_channel_block[1], | |
kernel_size=3, stride=1, | |
padding=1, | |
weight_attr=conv_weight_attr, | |
bias_attr=False,) | |
self.bn2 = nn.BatchNorm2D(self.output_channel_block[1]) | |
self.maxpool3 = nn.MaxPool2D(kernel_size=2, | |
stride=(2, 1), | |
padding=(0, 1)) | |
self.layer3 = self._make_layer(block, self.output_channel_block[2], | |
layers[2], stride=1) | |
self.conv3 = nn.Conv2D(self.output_channel_block[2], | |
self.output_channel_block[2], | |
kernel_size=3, stride=1, | |
padding=1, | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn3 = nn.BatchNorm2D(self.output_channel_block[2]) | |
self.layer4 = self._make_layer(block, self.output_channel_block[3], | |
layers[3], stride=1) | |
self.conv4_1 = nn.Conv2D(self.output_channel_block[3], | |
self.output_channel_block[3], | |
kernel_size=2, stride=(2, 1), | |
padding=(0, 1), | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn4_1 = nn.BatchNorm2D(self.output_channel_block[3]) | |
self.conv4_2 = nn.Conv2D(self.output_channel_block[3], | |
self.output_channel_block[3], | |
kernel_size=2, stride=1, | |
padding=0, | |
weight_attr=conv_weight_attr, | |
bias_attr=False) | |
self.bn4_2 = nn.BatchNorm2D(self.output_channel_block[3]) | |
def _make_layer(self, block, planes, blocks, stride=1): | |
""" | |
Args: | |
block (block): convolution block | |
planes (int): input channels | |
blocks (list): layers of the block | |
stride (int): stride of the convolution | |
Returns: | |
nn.Sequential: the combination of the convolution block | |
""" | |
downsample = None | |
if stride != 1 or self.inplanes != planes * block.expansion: | |
downsample = nn.Sequential( | |
nn.Conv2D(self.inplanes, planes * block.expansion, | |
kernel_size=1, stride=stride, | |
weight_attr=conv_weight_attr, | |
bias_attr=False), | |
nn.BatchNorm2D(planes * block.expansion), | |
) | |
layers = list() | |
layers.append(block(self.inplanes, planes, stride, downsample)) | |
self.inplanes = planes * block.expansion | |
for _ in range(1, blocks): | |
layers.append(block(self.inplanes, planes)) | |
return nn.Sequential(*layers) | |
def forward(self, x): | |
x = self.conv0_1(x) | |
x = self.bn0_1(x) | |
x = self.relu(x) | |
x = self.conv0_2(x) | |
x = self.bn0_2(x) | |
x = self.relu(x) | |
x = self.maxpool1(x) | |
x = self.layer1(x) | |
x = self.conv1(x) | |
x = self.bn1(x) | |
x = self.relu(x) | |
x = self.maxpool2(x) | |
x = self.layer2(x) | |
x = self.conv2(x) | |
x = self.bn2(x) | |
x = self.relu(x) | |
x = self.maxpool3(x) | |
x = self.layer3(x) | |
x = self.conv3(x) | |
x = self.bn3(x) | |
x = self.relu(x) | |
x = self.layer4(x) | |
x = self.conv4_1(x) | |
x = self.bn4_1(x) | |
x = self.relu(x) | |
x = self.conv4_2(x) | |
x = self.bn4_2(x) | |
x = self.relu(x) | |
return x | |