import torch
from torch import nn
[docs]class ChannelAttention(nn.Module):
def __init__(self, num_features, reduction):
super(ChannelAttention, self).__init__()
self.module = nn.Sequential(
nn.AdaptiveAvgPool2d(1),
nn.Conv2d(num_features, num_features // reduction, kernel_size=1),
nn.ReLU(inplace=True),
nn.Conv2d(num_features // reduction, num_features, kernel_size=1),
nn.Sigmoid()
)
[docs] def forward(self, x):
return x * self.module(x)
[docs]class RCAB(nn.Module):
def __init__(self, num_features, reduction):
super(RCAB, self).__init__()
self.module = nn.Sequential(
nn.Conv2d(num_features, num_features, kernel_size=3, padding="same"),
nn.ReLU(inplace=True),
nn.Conv2d(num_features, num_features, kernel_size=3, padding="same"),
ChannelAttention(num_features, reduction)
)
[docs] def forward(self, x):
return x + self.module(x)
[docs]class RG(nn.Module):
def __init__(self, num_features, num_rcab, reduction):
super(RG, self).__init__()
self.module = [RCAB(num_features, reduction) for _ in range(num_rcab)]
self.module.append(nn.Conv2d(num_features, num_features, kernel_size=3, padding="same"))
self.module = nn.Sequential(*self.module)
[docs] def forward(self, x):
return x + self.module(x)
[docs]class rcan(nn.Module):
"""
Deep residual channel attention networks (RCAN) model.
Reference: `Image Super-Resolution Using Very Deep Residual Channel Attention Networks
<https://openaccess.thecvf.com/content_ECCV_2018/html/Yulun_Zhang_Image_Super-Resolution_Using_ECCV_2018_paper.html>`_.
Adapted from `here <https://github.com/yjn870/RCAN-pytorch>`_.
"""
def __init__(self, ndim, num_channels=3, filters=64, scale=2, n_sub_block=2, num_rcab=20, reduction=16):
super(rcan, self).__init__()
if type(scale) is tuple:
scale = scale[0]
self.ndim = ndim
self.sf = nn.Conv2d(num_channels, filters, kernel_size=3, padding="same")
self.rgs = nn.Sequential(*[RG(filters, num_rcab, reduction) for _ in range(n_sub_block)])
self.conv1 = nn.Conv2d(filters, filters, kernel_size=3, padding="same")
self.upscale = nn.Sequential(
nn.Conv2d(filters, filters * (scale ** 2), kernel_size=3, padding="same"),
nn.PixelShuffle(scale)
)
self.conv2 = nn.Conv2d(filters, num_channels, kernel_size=3, padding="same")
[docs] def forward(self, x):
x = self.sf(x)
residual = x
x = self.rgs(x)
x = self.conv1(x)
x += residual
x = self.upscale(x)
x = self.conv2(x)
return x