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IDM-VTON
update IDM-VTON Demo
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# Copyright (c) Facebook, Inc. and its affiliates.
import math
import fvcore.nn.weight_init as weight_init
import torch
import torch.nn.functional as F
from torch import nn
from detectron2.layers import Conv2d, ShapeSpec, get_norm
from .backbone import Backbone
from .build import BACKBONE_REGISTRY
from .resnet import build_resnet_backbone
__all__ = ["build_resnet_fpn_backbone", "build_retinanet_resnet_fpn_backbone", "FPN"]
class FPN(Backbone):
"""
This module implements :paper:`FPN`.
It creates pyramid features built on top of some input feature maps.
"""
_fuse_type: torch.jit.Final[str]
def __init__(
self,
bottom_up,
in_features,
out_channels,
norm="",
top_block=None,
fuse_type="sum",
square_pad=0,
):
"""
Args:
bottom_up (Backbone): module representing the bottom up subnetwork.
Must be a subclass of :class:`Backbone`. The multi-scale feature
maps generated by the bottom up network, and listed in `in_features`,
are used to generate FPN levels.
in_features (list[str]): names of the input feature maps coming
from the backbone to which FPN is attached. For example, if the
backbone produces ["res2", "res3", "res4"], any *contiguous* sublist
of these may be used; order must be from high to low resolution.
out_channels (int): number of channels in the output feature maps.
norm (str): the normalization to use.
top_block (nn.Module or None): if provided, an extra operation will
be performed on the output of the last (smallest resolution)
FPN output, and the result will extend the result list. The top_block
further downsamples the feature map. It must have an attribute
"num_levels", meaning the number of extra FPN levels added by
this block, and "in_feature", which is a string representing
its input feature (e.g., p5).
fuse_type (str): types for fusing the top down features and the lateral
ones. It can be "sum" (default), which sums up element-wise; or "avg",
which takes the element-wise mean of the two.
square_pad (int): If > 0, require input images to be padded to specific square size.
"""
super(FPN, self).__init__()
assert isinstance(bottom_up, Backbone)
assert in_features, in_features
# Feature map strides and channels from the bottom up network (e.g. ResNet)
input_shapes = bottom_up.output_shape()
strides = [input_shapes[f].stride for f in in_features]
in_channels_per_feature = [input_shapes[f].channels for f in in_features]
_assert_strides_are_log2_contiguous(strides)
lateral_convs = []
output_convs = []
use_bias = norm == ""
for idx, in_channels in enumerate(in_channels_per_feature):
lateral_norm = get_norm(norm, out_channels)
output_norm = get_norm(norm, out_channels)
lateral_conv = Conv2d(
in_channels, out_channels, kernel_size=1, bias=use_bias, norm=lateral_norm
)
output_conv = Conv2d(
out_channels,
out_channels,
kernel_size=3,
stride=1,
padding=1,
bias=use_bias,
norm=output_norm,
)
weight_init.c2_xavier_fill(lateral_conv)
weight_init.c2_xavier_fill(output_conv)
stage = int(math.log2(strides[idx]))
self.add_module("fpn_lateral{}".format(stage), lateral_conv)
self.add_module("fpn_output{}".format(stage), output_conv)
lateral_convs.append(lateral_conv)
output_convs.append(output_conv)
# Place convs into top-down order (from low to high resolution)
# to make the top-down computation in forward clearer.
self.lateral_convs = lateral_convs[::-1]
self.output_convs = output_convs[::-1]
self.top_block = top_block
self.in_features = tuple(in_features)
self.bottom_up = bottom_up
# Return feature names are "p<stage>", like ["p2", "p3", ..., "p6"]
self._out_feature_strides = {"p{}".format(int(math.log2(s))): s for s in strides}
# top block output feature maps.
if self.top_block is not None:
for s in range(stage, stage + self.top_block.num_levels):
self._out_feature_strides["p{}".format(s + 1)] = 2 ** (s + 1)
self._out_features = list(self._out_feature_strides.keys())
self._out_feature_channels = {k: out_channels for k in self._out_features}
self._size_divisibility = strides[-1]
self._square_pad = square_pad
assert fuse_type in {"avg", "sum"}
self._fuse_type = fuse_type
@property
def size_divisibility(self):
return self._size_divisibility
@property
def padding_constraints(self):
return {"square_size": self._square_pad}
def forward(self, x):
"""
Args:
input (dict[str->Tensor]): mapping feature map name (e.g., "res5") to
feature map tensor for each feature level in high to low resolution order.
Returns:
dict[str->Tensor]:
mapping from feature map name to FPN feature map tensor
in high to low resolution order. Returned feature names follow the FPN
paper convention: "p<stage>", where stage has stride = 2 ** stage e.g.,
["p2", "p3", ..., "p6"].
"""
bottom_up_features = self.bottom_up(x)
results = []
prev_features = self.lateral_convs[0](bottom_up_features[self.in_features[-1]])
results.append(self.output_convs[0](prev_features))
# Reverse feature maps into top-down order (from low to high resolution)
for idx, (lateral_conv, output_conv) in enumerate(
zip(self.lateral_convs, self.output_convs)
):
# Slicing of ModuleList is not supported https://github.com/pytorch/pytorch/issues/47336
# Therefore we loop over all modules but skip the first one
if idx > 0:
features = self.in_features[-idx - 1]
features = bottom_up_features[features]
top_down_features = F.interpolate(prev_features, scale_factor=2.0, mode="nearest")
lateral_features = lateral_conv(features)
prev_features = lateral_features + top_down_features
if self._fuse_type == "avg":
prev_features /= 2
results.insert(0, output_conv(prev_features))
if self.top_block is not None:
if self.top_block.in_feature in bottom_up_features:
top_block_in_feature = bottom_up_features[self.top_block.in_feature]
else:
top_block_in_feature = results[self._out_features.index(self.top_block.in_feature)]
results.extend(self.top_block(top_block_in_feature))
assert len(self._out_features) == len(results)
return {f: res for f, res in zip(self._out_features, results)}
def output_shape(self):
return {
name: ShapeSpec(
channels=self._out_feature_channels[name], stride=self._out_feature_strides[name]
)
for name in self._out_features
}
def _assert_strides_are_log2_contiguous(strides):
"""
Assert that each stride is 2x times its preceding stride, i.e. "contiguous in log2".
"""
for i, stride in enumerate(strides[1:], 1):
assert stride == 2 * strides[i - 1], "Strides {} {} are not log2 contiguous".format(
stride, strides[i - 1]
)
class LastLevelMaxPool(nn.Module):
"""
This module is used in the original FPN to generate a downsampled
P6 feature from P5.
"""
def __init__(self):
super().__init__()
self.num_levels = 1
self.in_feature = "p5"
def forward(self, x):
return [F.max_pool2d(x, kernel_size=1, stride=2, padding=0)]
class LastLevelP6P7(nn.Module):
"""
This module is used in RetinaNet to generate extra layers, P6 and P7 from
C5 feature.
"""
def __init__(self, in_channels, out_channels, in_feature="res5"):
super().__init__()
self.num_levels = 2
self.in_feature = in_feature
self.p6 = nn.Conv2d(in_channels, out_channels, 3, 2, 1)
self.p7 = nn.Conv2d(out_channels, out_channels, 3, 2, 1)
for module in [self.p6, self.p7]:
weight_init.c2_xavier_fill(module)
def forward(self, c5):
p6 = self.p6(c5)
p7 = self.p7(F.relu(p6))
return [p6, p7]
@BACKBONE_REGISTRY.register()
def build_resnet_fpn_backbone(cfg, input_shape: ShapeSpec):
"""
Args:
cfg: a detectron2 CfgNode
Returns:
backbone (Backbone): backbone module, must be a subclass of :class:`Backbone`.
"""
bottom_up = build_resnet_backbone(cfg, input_shape)
in_features = cfg.MODEL.FPN.IN_FEATURES
out_channels = cfg.MODEL.FPN.OUT_CHANNELS
backbone = FPN(
bottom_up=bottom_up,
in_features=in_features,
out_channels=out_channels,
norm=cfg.MODEL.FPN.NORM,
top_block=LastLevelMaxPool(),
fuse_type=cfg.MODEL.FPN.FUSE_TYPE,
)
return backbone
@BACKBONE_REGISTRY.register()
def build_retinanet_resnet_fpn_backbone(cfg, input_shape: ShapeSpec):
"""
Args:
cfg: a detectron2 CfgNode
Returns:
backbone (Backbone): backbone module, must be a subclass of :class:`Backbone`.
"""
bottom_up = build_resnet_backbone(cfg, input_shape)
in_features = cfg.MODEL.FPN.IN_FEATURES
out_channels = cfg.MODEL.FPN.OUT_CHANNELS
in_channels_p6p7 = bottom_up.output_shape()["res5"].channels
backbone = FPN(
bottom_up=bottom_up,
in_features=in_features,
out_channels=out_channels,
norm=cfg.MODEL.FPN.NORM,
top_block=LastLevelP6P7(in_channels_p6p7, out_channels),
fuse_type=cfg.MODEL.FPN.FUSE_TYPE,
)
return backbone