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# Copyright (c) OpenMMLab. All rights reserved.
import torch.nn as nn
import torch.nn.functional as F
from ..utils import xavier_init
from .registry import UPSAMPLE_LAYERS
UPSAMPLE_LAYERS.register_module('nearest', module=nn.Upsample)
UPSAMPLE_LAYERS.register_module('bilinear', module=nn.Upsample)
@UPSAMPLE_LAYERS.register_module(name='pixel_shuffle')
class PixelShufflePack(nn.Module):
"""Pixel Shuffle upsample layer.
This module packs `F.pixel_shuffle()` and a nn.Conv2d module together to
achieve a simple upsampling with pixel shuffle.
Args:
in_channels (int): Number of input channels.
out_channels (int): Number of output channels.
scale_factor (int): Upsample ratio.
upsample_kernel (int): Kernel size of the conv layer to expand the
channels.
"""
def __init__(self, in_channels, out_channels, scale_factor,
upsample_kernel):
super(PixelShufflePack, self).__init__()
self.in_channels = in_channels
self.out_channels = out_channels
self.scale_factor = scale_factor
self.upsample_kernel = upsample_kernel
self.upsample_conv = nn.Conv2d(
self.in_channels,
self.out_channels * scale_factor * scale_factor,
self.upsample_kernel,
padding=(self.upsample_kernel - 1) // 2)
self.init_weights()
def init_weights(self):
xavier_init(self.upsample_conv, distribution='uniform')
def forward(self, x):
x = self.upsample_conv(x)
x = F.pixel_shuffle(x, self.scale_factor)
return x
def build_upsample_layer(cfg, *args, **kwargs):
"""Build upsample layer.
Args:
cfg (dict): The upsample layer config, which should contain:
- type (str): Layer type.
- scale_factor (int): Upsample ratio, which is not applicable to
deconv.
- layer args: Args needed to instantiate a upsample layer.
args (argument list): Arguments passed to the ``__init__``
method of the corresponding conv layer.
kwargs (keyword arguments): Keyword arguments passed to the
``__init__`` method of the corresponding conv layer.
Returns:
nn.Module: Created upsample layer.
"""
if not isinstance(cfg, dict):
raise TypeError(f'cfg must be a dict, but got {type(cfg)}')
if 'type' not in cfg:
raise KeyError(
f'the cfg dict must contain the key "type", but got {cfg}')
cfg_ = cfg.copy()
layer_type = cfg_.pop('type')
if layer_type not in UPSAMPLE_LAYERS:
raise KeyError(f'Unrecognized upsample type {layer_type}')
else:
upsample = UPSAMPLE_LAYERS.get(layer_type)
if upsample is nn.Upsample:
cfg_['mode'] = layer_type
layer = upsample(*args, **kwargs, **cfg_)
return layer
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