import torch.nn as nn
def conv3x3(inplanes, outplanes, stride=1):
"""A simple wrapper for 3x3 convolution with padding.
Args:
inplanes (int): Channel number of inputs.
outplanes (int): Channel number of outputs.
stride (int): Stride in convolution. Default: 1.
"""
return nn.Conv2d(
inplanes, outplanes, kernel_size=3, stride=stride, padding=1, bias=False
)
class BasicBlock(nn.Module):
"""Basic residual block used in the ResNetArcFace architecture.
Args:
inplanes (int): Channel number of inputs.
planes (int): Channel number of outputs.
stride (int): Stride in convolution. Default: 1.
downsample (nn.Module): The downsample module. Default: None.
"""
expansion = 1 # output channel expansion ratio
def __init__(self, inplanes, planes, stride=1, downsample=None):
super(BasicBlock, self).__init__()
self.conv1 = conv3x3(inplanes, planes, stride)
self.bn1 = nn.BatchNorm2d(planes)
self.relu = nn.ReLU(inplace=True)
self.conv2 = conv3x3(planes, planes)
self.bn2 = nn.BatchNorm2d(planes)
self.downsample = downsample
self.stride = stride
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 IRBlock(nn.Module):
"""Improved residual block (IR Block) used in the ResNetArcFace architecture.
Args:
inplanes (int): Channel number of inputs.
planes (int): Channel number of outputs.
stride (int): Stride in convolution. Default: 1.
downsample (nn.Module): The downsample module. Default: None.
use_se (bool): Whether use the SEBlock (squeeze and excitation block). Default: True.
"""
expansion = 1 # output channel expansion ratio
def __init__(self, inplanes, planes, stride=1, downsample=None, use_se=True):
super(IRBlock, self).__init__()
self.bn0 = nn.BatchNorm2d(inplanes)
self.conv1 = conv3x3(inplanes, inplanes)
self.bn1 = nn.BatchNorm2d(inplanes)
self.prelu = nn.PReLU()
self.conv2 = conv3x3(inplanes, planes, stride)
self.bn2 = nn.BatchNorm2d(planes)
self.downsample = downsample
self.stride = stride
self.use_se = use_se
if self.use_se:
self.se = SEBlock(planes)
def forward(self, x):
residual = x
out = self.bn0(x)
out = self.conv1(out)
out = self.bn1(out)
out = self.prelu(out)
out = self.conv2(out)
out = self.bn2(out)
if self.use_se:
out = self.se(out)
if self.downsample is not None:
residual = self.downsample(x)
out += residual
out = self.prelu(out)
return out
class Bottleneck(nn.Module):
"""Bottleneck block used in the ResNetArcFace architecture.
Args:
inplanes (int): Channel number of inputs.
planes (int): Channel number of outputs.
stride (int): Stride in convolution. Default: 1.
downsample (nn.Module): The downsample module. Default: None.
"""
expansion = 4 # output channel expansion ratio
def __init__(self, inplanes, planes, stride=1, downsample=None):
super(Bottleneck, self).__init__()
self.conv1 = nn.Conv2d(inplanes, planes, kernel_size=1, bias=False)
self.bn1 = nn.BatchNorm2d(planes)
self.conv2 = nn.Conv2d(
planes, planes, kernel_size=3, stride=stride, padding=1, bias=False
)
self.bn2 = nn.BatchNorm2d(planes)
self.conv3 = nn.Conv2d(
planes, planes * self.expansion, kernel_size=1, bias=False
)
self.bn3 = nn.BatchNorm2d(planes * self.expansion)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
self.stride = stride
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)
out = self.relu(out)
out = self.conv3(out)
out = self.bn3(out)
if self.downsample is not None:
residual = self.downsample(x)
out += residual
out = self.relu(out)
return out
class SEBlock(nn.Module):
"""The squeeze-and-excitation block (SEBlock) used in the IRBlock.
Args:
channel (int): Channel number of inputs.
reduction (int): Channel reduction ration. Default: 16.
"""
def __init__(self, channel, reduction=16):
super(SEBlock, self).__init__()
self.avg_pool = nn.AdaptiveAvgPool2d(
1
) # pool to 1x1 without spatial information
self.fc = nn.Sequential(
nn.Linear(channel, channel // reduction),
nn.PReLU(),
nn.Linear(channel // reduction, channel),
nn.Sigmoid(),
)
def forward(self, x):
b, c, _, _ = x.size()
y = self.avg_pool(x).view(b, c)
y = self.fc(y).view(b, c, 1, 1)
return x * y
class ResNetArcFace(nn.Module):
"""ArcFace with ResNet architectures.
Ref: ArcFace: Additive Angular Margin Loss for Deep Face Recognition.
Args:
block (str): Block used in the ArcFace architecture.
layers (tuple(int)): Block numbers in each layer.
use_se (bool): Whether use the SEBlock (squeeze and excitation block). Default: True.
"""
def __init__(self, block, layers, use_se=True):
if block == "IRBlock":
block = IRBlock
self.inplanes = 64
self.use_se = use_se
super(ResNetArcFace, self).__init__()
self.conv1 = nn.Conv2d(1, 64, kernel_size=3, padding=1, bias=False)
self.bn1 = nn.BatchNorm2d(64)
self.prelu = nn.PReLU()
self.maxpool = nn.MaxPool2d(kernel_size=2, stride=2)
self.layer1 = self._make_layer(block, 64, layers[0])
self.layer2 = self._make_layer(block, 128, layers[1], stride=2)
self.layer3 = self._make_layer(block, 256, layers[2], stride=2)
self.layer4 = self._make_layer(block, 512, layers[3], stride=2)
self.bn4 = nn.BatchNorm2d(512)
self.dropout = nn.Dropout()
self.fc5 = nn.Linear(512 * 8 * 8, 512)
self.bn5 = nn.BatchNorm1d(512)
# initialization
for m in self.modules():
if isinstance(m, nn.Conv2d):
nn.init.xavier_normal_(m.weight)
elif isinstance(m, nn.BatchNorm2d) or isinstance(m, nn.BatchNorm1d):
nn.init.constant_(m.weight, 1)
nn.init.constant_(m.bias, 0)
elif isinstance(m, nn.Linear):
nn.init.xavier_normal_(m.weight)
nn.init.constant_(m.bias, 0)
def _make_layer(self, block, planes, num_blocks, stride=1):
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,
bias=False,
),
nn.BatchNorm2d(planes * block.expansion),
)
layers = []
layers.append(
block(self.inplanes, planes, stride, downsample, use_se=self.use_se)
)
self.inplanes = planes
for _ in range(1, num_blocks):
layers.append(block(self.inplanes, planes, use_se=self.use_se))
return nn.Sequential(*layers)
def forward(self, x):
x = self.conv1(x)
x = self.bn1(x)
x = self.prelu(x)
x = self.maxpool(x)
x = self.layer1(x)
x = self.layer2(x)
x = self.layer3(x)
x = self.layer4(x)
x = self.bn4(x)
x = self.dropout(x)
x = x.view(x.size(0), -1)
x = self.fc5(x)
x = self.bn5(x)
return x