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import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import transforms
from torchvision import utils as vutils
from model import common
from utils.tools import extract_image_patches,\
reduce_mean, reduce_sum, same_padding
class PyramidAttention(nn.Module):
def __init__(self, level=5, res_scale=1, channel=64, reduction=2, ksize=3, stride=1, softmax_scale=10, average=True, conv=common.default_conv):
super(PyramidAttention, self).__init__()
self.ksize = ksize
self.stride = stride
self.res_scale = res_scale
self.softmax_scale = softmax_scale
self.scale = [1-i/10 for i in range(level)]
self.average = average
escape_NaN = torch.FloatTensor([1e-4])
self.register_buffer('escape_NaN', escape_NaN)
self.conv_match_L_base = common.BasicBlock(conv,channel,channel//reduction, 1, bn=False, act=nn.PReLU())
self.conv_match = common.BasicBlock(conv,channel, channel//reduction, 1, bn=False, act=nn.PReLU())
self.conv_assembly = common.BasicBlock(conv,channel, channel,1,bn=False, act=nn.PReLU())
def forward(self, input):
res = input
#theta
match_base = self.conv_match_L_base(input)
shape_base = list(res.size())
input_groups = torch.split(match_base,1,dim=0)
# patch size for matching
kernel = self.ksize
# raw_w is for reconstruction
raw_w = []
# w is for matching
w = []
#build feature pyramid
for i in range(len(self.scale)):
ref = input
if self.scale[i]!=1:
ref = F.interpolate(input, scale_factor=self.scale[i], mode='bicubic')
#feature transformation function f
base = self.conv_assembly(ref)
shape_input = base.shape
#sampling
raw_w_i = extract_image_patches(base, ksizes=[kernel, kernel],
strides=[self.stride,self.stride],
rates=[1, 1],
padding='same') # [N, C*k*k, L]
raw_w_i = raw_w_i.view(shape_input[0], shape_input[1], kernel, kernel, -1)
raw_w_i = raw_w_i.permute(0, 4, 1, 2, 3) # raw_shape: [N, L, C, k, k]
raw_w_i_groups = torch.split(raw_w_i, 1, dim=0)
raw_w.append(raw_w_i_groups)
#feature transformation function g
ref_i = self.conv_match(ref)
shape_ref = ref_i.shape
#sampling
w_i = extract_image_patches(ref_i, ksizes=[self.ksize, self.ksize],
strides=[self.stride, self.stride],
rates=[1, 1],
padding='same')
w_i = w_i.view(shape_ref[0], shape_ref[1], self.ksize, self.ksize, -1)
w_i = w_i.permute(0, 4, 1, 2, 3) # w shape: [N, L, C, k, k]
w_i_groups = torch.split(w_i, 1, dim=0)
w.append(w_i_groups)
y = []
for idx, xi in enumerate(input_groups):
#group in a filter
wi = torch.cat([w[i][idx][0] for i in range(len(self.scale))],dim=0) # [L, C, k, k]
#normalize
max_wi = torch.max(torch.sqrt(reduce_sum(torch.pow(wi, 2),
axis=[1, 2, 3],
keepdim=True)),
self.escape_NaN)
wi_normed = wi/ max_wi
#matching
xi = same_padding(xi, [self.ksize, self.ksize], [1, 1], [1, 1]) # xi: 1*c*H*W
yi = F.conv2d(xi, wi_normed, stride=1) # [1, L, H, W] L = shape_ref[2]*shape_ref[3]
yi = yi.view(1,wi.shape[0], shape_base[2], shape_base[3]) # (B=1, C=32*32, H=32, W=32)
# softmax matching score
yi = F.softmax(yi*self.softmax_scale, dim=1)
if self.average == False:
yi = (yi == yi.max(dim=1,keepdim=True)[0]).float()
# deconv for patch pasting
raw_wi = torch.cat([raw_w[i][idx][0] for i in range(len(self.scale))],dim=0)
yi = F.conv_transpose2d(yi, raw_wi, stride=self.stride,padding=1)/4.
y.append(yi)
y = torch.cat(y, dim=0)+res*self.res_scale # back to the mini-batch
return y |