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# Copyright (c) OpenMMLab. All rights reserved.
import math
from typing import Sequence
from itertools import repeat
import collections.abc
import torch.nn as nn
import torch.nn.functional as F
from ..model.base_module import BaseModule
from .activation import build_conv_layer, build_norm_layer
class AdaptivePadding(nn.Module):
"""Applies padding to input (if needed) so that input can get fully covered
by filter you specified. It supports two modes "same" and "corner". The
"same" mode is same with "SAME" padding mode in TensorFlow, pad zero around
input. The "corner" mode would pad zero to bottom right.
Args:
kernel_size (int | tuple): Size of the kernel:
stride (int | tuple): Stride of the filter. Default: 1:
dilation (int | tuple): Spacing between kernel elements.
Default: 1.
padding (str): Support "same" and "corner", "corner" mode
would pad zero to bottom right, and "same" mode would
pad zero around input. Default: "corner".
Example:
>>> kernel_size = 16
>>> stride = 16
>>> dilation = 1
>>> input = torch.rand(1, 1, 15, 17)
>>> adap_pad = AdaptivePadding(
>>> kernel_size=kernel_size,
>>> stride=stride,
>>> dilation=dilation,
>>> padding="corner")
>>> out = adap_pad(input)
>>> assert (out.shape[2], out.shape[3]) == (16, 32)
>>> input = torch.rand(1, 1, 16, 17)
>>> out = adap_pad(input)
>>> assert (out.shape[2], out.shape[3]) == (16, 32)
"""
def __init__(self, kernel_size=1, stride=1, dilation=1, padding='corner'):
super().__init__()
assert padding in ('same', 'corner')
kernel_size = to_2tuple(kernel_size)
stride = to_2tuple(stride)
dilation = to_2tuple(dilation)
self.padding = padding
self.kernel_size = kernel_size
self.stride = stride
self.dilation = dilation
def get_pad_shape(self, input_shape):
input_h, input_w = input_shape
kernel_h, kernel_w = self.kernel_size
stride_h, stride_w = self.stride
output_h = math.ceil(input_h / stride_h)
output_w = math.ceil(input_w / stride_w)
pad_h = max((output_h - 1) * stride_h +
(kernel_h - 1) * self.dilation[0] + 1 - input_h, 0)
pad_w = max((output_w - 1) * stride_w +
(kernel_w - 1) * self.dilation[1] + 1 - input_w, 0)
return pad_h, pad_w
def forward(self, x):
pad_h, pad_w = self.get_pad_shape(x.size()[-2:])
if pad_h > 0 or pad_w > 0:
if self.padding == 'corner':
x = F.pad(x, [0, pad_w, 0, pad_h])
elif self.padding == 'same':
x = F.pad(x, [
pad_w // 2, pad_w - pad_w // 2, pad_h // 2,
pad_h - pad_h // 2
])
return x
class PatchEmbed(BaseModule):
"""Image to Patch Embedding.
We use a conv layer to implement PatchEmbed.
Args:
in_channels (int): The num of input channels. Default: 3
embed_dims (int): The dimensions of embedding. Default: 768
conv_type (str): The config dict for embedding
conv layer type selection. Default: "Conv2d".
kernel_size (int): The kernel_size of embedding conv. Default: 16.
stride (int, optional): The slide stride of embedding conv.
Default: None (Would be set as `kernel_size`).
padding (int | tuple | string ): The padding length of
embedding conv. When it is a string, it means the mode
of adaptive padding, support "same" and "corner" now.
Default: "corner".
dilation (int): The dilation rate of embedding conv. Default: 1.
bias (bool): Bias of embed conv. Default: True.
norm_cfg (dict, optional): Config dict for normalization layer.
Default: None.
input_size (int | tuple | None): The size of input, which will be
used to calculate the out size. Only work when `dynamic_size`
is False. Default: None.
init_cfg (`mmengine.ConfigDict`, optional): The Config for
initialization. Default: None.
"""
def __init__(self,
in_channels=3,
embed_dims=768,
conv_type='Conv2d',
kernel_size=16,
stride=None,
padding='corner',
dilation=1,
bias=True,
norm_cfg=None,
input_size=None,
init_cfg=None):
super().__init__(init_cfg=init_cfg)
self.embed_dims = embed_dims
if stride is None:
stride = kernel_size
kernel_size = to_2tuple(kernel_size)
stride = to_2tuple(stride)
dilation = to_2tuple(dilation)
if isinstance(padding, str):
self.adap_padding = AdaptivePadding(
kernel_size=kernel_size,
stride=stride,
dilation=dilation,
padding=padding)
# disable the padding of conv
padding = 0
else:
self.adap_padding = None
padding = to_2tuple(padding)
self.projection = build_conv_layer(
dict(type=conv_type),
in_channels=in_channels,
out_channels=embed_dims,
kernel_size=kernel_size,
stride=stride,
padding=padding,
dilation=dilation,
bias=bias)
if norm_cfg is not None:
self.norm = build_norm_layer(norm_cfg, embed_dims)[1]
else:
self.norm = None
if input_size:
input_size = to_2tuple(input_size)
# `init_out_size` would be used outside to
# calculate the num_patches
# when `use_abs_pos_embed` outside
self.init_input_size = input_size
if self.adap_padding:
pad_h, pad_w = self.adap_padding.get_pad_shape(input_size)
input_h, input_w = input_size
input_h = input_h + pad_h
input_w = input_w + pad_w
input_size = (input_h, input_w)
# https://pytorch.org/docs/stable/generated/torch.nn.Conv2d.html
h_out = (input_size[0] + 2 * padding[0] - dilation[0] *
(kernel_size[0] - 1) - 1) // stride[0] + 1
w_out = (input_size[1] + 2 * padding[1] - dilation[1] *
(kernel_size[1] - 1) - 1) // stride[1] + 1
self.init_out_size = (h_out, w_out)
else:
self.init_input_size = None
self.init_out_size = None
def forward(self, x):
"""
Args:
x (Tensor): Has shape (B, C, H, W). In most case, C is 3.
Returns:
tuple: Contains merged results and its spatial shape.
- x (Tensor): Has shape (B, out_h * out_w, embed_dims)
- out_size (tuple[int]): Spatial shape of x, arrange as
(out_h, out_w).
"""
if self.adap_padding:
x = self.adap_padding(x)
x = self.projection(x)
out_size = (x.shape[2], x.shape[3])
x = x.flatten(2).transpose(1, 2)
if self.norm is not None:
x = self.norm(x)
return x, out_size
# From PyTorch internals
def _ntuple(n):
def parse(x):
if isinstance(x, collections.abc.Iterable):
return x
return tuple(repeat(x, n))
return parse
to_2tuple = _ntuple(2)
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