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from torch import nn
import torch.nn.functional as F
import torch
from sync_batchnorm import SynchronizedBatchNorm2d as BatchNorm2d
def kp2gaussian(kp, spatial_size, kp_variance):
"""
Transform a keypoint into gaussian like representation
"""
mean = kp['value']
coordinate_grid = make_coordinate_grid(spatial_size, mean.type())
number_of_leading_dimensions = len(mean.shape) - 1
shape = (1,) * number_of_leading_dimensions + coordinate_grid.shape
coordinate_grid = coordinate_grid.view(*shape)
repeats = mean.shape[:number_of_leading_dimensions] + (1, 1, 1)
coordinate_grid = coordinate_grid.repeat(*repeats)
# Preprocess kp shape
shape = mean.shape[:number_of_leading_dimensions] + (1, 1, 2)
mean = mean.view(*shape)
mean_sub = (coordinate_grid - mean)
out = torch.exp(-0.5 * (mean_sub ** 2).sum(-1) / kp_variance)
return out
def make_coordinate_grid(spatial_size, type):
"""
Create a meshgrid [-1,1] x [-1,1] of given spatial_size.
"""
h, w = spatial_size
x = torch.arange(w).type(type)
y = torch.arange(h).type(type)
x = (2 * (x / (w - 1)) - 1)
y = (2 * (y / (h - 1)) - 1)
yy = y.view(-1, 1).repeat(1, w)
xx = x.view(1, -1).repeat(h, 1)
meshed = torch.cat([xx.unsqueeze_(2), yy.unsqueeze_(2)], 2)
return meshed
class ResBlock2d(nn.Module):
"""
Res block, preserve spatial resolution.
"""
def __init__(self, in_features, kernel_size, padding):
super(ResBlock2d, self).__init__()
self.conv1 = nn.Conv2d(in_channels=in_features, out_channels=in_features, kernel_size=kernel_size,
padding=padding)
self.conv2 = nn.Conv2d(in_channels=in_features, out_channels=in_features, kernel_size=kernel_size,
padding=padding)
self.norm1 = BatchNorm2d(in_features, affine=True)
self.norm2 = BatchNorm2d(in_features, affine=True)
def forward(self, x):
out = self.norm1(x)
out = F.relu(out)
out = self.conv1(out)
out = self.norm2(out)
out = F.relu(out)
out = self.conv2(out)
out += x
return out
class UpBlock2d(nn.Module):
"""
Upsampling block for use in decoder.
"""
def __init__(self, in_features, out_features, kernel_size=3, padding=1, groups=1):
super(UpBlock2d, self).__init__()
self.conv = nn.Conv2d(in_channels=in_features, out_channels=out_features, kernel_size=kernel_size,
padding=padding, groups=groups)
self.norm = BatchNorm2d(out_features, affine=True)
def forward(self, x):
out = F.interpolate(x, scale_factor=2)
out = self.conv(out)
out = self.norm(out)
out = F.relu(out)
return out
class DownBlock2d(nn.Module):
"""
Downsampling block for use in encoder.
"""
def __init__(self, in_features, out_features, kernel_size=3, padding=1, groups=1):
super(DownBlock2d, self).__init__()
self.conv = nn.Conv2d(in_channels=in_features, out_channels=out_features, kernel_size=kernel_size,
padding=padding, groups=groups)
self.norm = BatchNorm2d(out_features, affine=True)
self.pool = nn.AvgPool2d(kernel_size=(2, 2))
def forward(self, x):
out = self.conv(x)
out = self.norm(out)
out = F.relu(out)
out = self.pool(out)
return out
class SameBlock2d(nn.Module):
"""
Simple block, preserve spatial resolution.
"""
def __init__(self, in_features, out_features, groups=1, kernel_size=3, padding=1):
super(SameBlock2d, self).__init__()
self.conv = nn.Conv2d(in_channels=in_features, out_channels=out_features,
kernel_size=kernel_size, padding=padding, groups=groups)
self.norm = BatchNorm2d(out_features, affine=True)
def forward(self, x):
out = self.conv(x)
out = self.norm(out)
out = F.relu(out)
return out
class Encoder(nn.Module):
"""
Hourglass Encoder
"""
def __init__(self, block_expansion, in_features, num_blocks=3, max_features=256):
super(Encoder, self).__init__()
down_blocks = []
for i in range(num_blocks):
down_blocks.append(DownBlock2d(in_features if i == 0 else min(max_features, block_expansion * (2 ** i)),
min(max_features, block_expansion * (2 ** (i + 1))),
kernel_size=3, padding=1))
self.down_blocks = nn.ModuleList(down_blocks)
def forward(self, x):
outs = [x]
for down_block in self.down_blocks:
outs.append(down_block(outs[-1]))
return outs
class Decoder(nn.Module):
"""
Hourglass Decoder
"""
def __init__(self, block_expansion, in_features, num_blocks=3, max_features=256):
super(Decoder, self).__init__()
up_blocks = []
for i in range(num_blocks)[::-1]:
in_filters = (1 if i == num_blocks - 1 else 2) * min(max_features, block_expansion * (2 ** (i + 1)))
out_filters = min(max_features, block_expansion * (2 ** i))
up_blocks.append(UpBlock2d(in_filters, out_filters, kernel_size=3, padding=1))
self.up_blocks = nn.ModuleList(up_blocks)
self.out_filters = block_expansion + in_features
def forward(self, x):
out = x.pop()
for up_block in self.up_blocks:
out = up_block(out)
skip = x.pop()
out = torch.cat([out, skip], dim=1)
return out
class Hourglass(nn.Module):
"""
Hourglass architecture.
"""
def __init__(self, block_expansion, in_features, num_blocks=3, max_features=256):
super(Hourglass, self).__init__()
self.encoder = Encoder(block_expansion, in_features, num_blocks, max_features)
self.decoder = Decoder(block_expansion, in_features, num_blocks, max_features)
self.out_filters = self.decoder.out_filters
def forward(self, x):
return self.decoder(self.encoder(x))
class AntiAliasInterpolation2d(nn.Module):
"""
Band-limited downsampling, for better preservation of the input signal.
"""
def __init__(self, channels, scale):
super(AntiAliasInterpolation2d, self).__init__()
sigma = (1 / scale - 1) / 2
kernel_size = 2 * round(sigma * 4) + 1
self.ka = kernel_size // 2
self.kb = self.ka - 1 if kernel_size % 2 == 0 else self.ka
kernel_size = [kernel_size, kernel_size]
sigma = [sigma, sigma]
# The gaussian kernel is the product of the
# gaussian function of each dimension.
kernel = 1
meshgrids = torch.meshgrid(
[
torch.arange(size, dtype=torch.float32)
for size in kernel_size
]
)
for size, std, mgrid in zip(kernel_size, sigma, meshgrids):
mean = (size - 1) / 2
kernel *= torch.exp(-(mgrid - mean) ** 2 / (2 * std ** 2))
# Make sure sum of values in gaussian kernel equals 1.
kernel = kernel / torch.sum(kernel)
# Reshape to depthwise convolutional weight
kernel = kernel.view(1, 1, *kernel.size())
kernel = kernel.repeat(channels, *[1] * (kernel.dim() - 1))
self.register_buffer('weight', kernel)
self.groups = channels
self.scale = scale
def forward(self, input):
if self.scale == 1.0:
return input
out = F.pad(input, (self.ka, self.kb, self.ka, self.kb))
out = F.conv2d(out, weight=self.weight, groups=self.groups)
out = F.interpolate(out, scale_factor=(self.scale, self.scale))
return out
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