pytorch-image-models/timm/layers/conv2d_same.py

""" Conv2d w/ Same Padding

Hacked together by / Copyright 2020 Ross Wightman
"""
import torch
import torch.nn as nn
import torch.nn.functional as F
from typing import Tuple, Optional

from .config import is_exportable, is_scriptable
from .padding import pad_same, pad_same_arg, get_padding_value


_USE_EXPORT_CONV = False


def conv2d_same(
        x,
        weight: torch.Tensor,
        bias: Optional[torch.Tensor] = None,
        stride: Tuple[int, int] = (1, 1),
        padding: Tuple[int, int] = (0, 0),
        dilation: Tuple[int, int] = (1, 1),
        groups: int = 1,
):
    x = pad_same(x, weight.shape[-2:], stride, dilation)
    return F.conv2d(x, weight, bias, stride, (0, 0), dilation, groups)


class Conv2dSame(nn.Conv2d):
    """ Tensorflow like 'SAME' convolution wrapper for 2D convolutions
    """

    def __init__(
            self,
            in_channels,
            out_channels,
            kernel_size,
            stride=1,
            padding=0,
            dilation=1,
            groups=1,
            bias=True,
    ):
        super(Conv2dSame, self).__init__(
            in_channels, out_channels, kernel_size,
            stride, 0, dilation, groups, bias,
        )

    def forward(self, x):
        return conv2d_same(
            x, self.weight, self.bias,
            self.stride, self.padding, self.dilation, self.groups,
        )


class Conv2dSameExport(nn.Conv2d):
    """ ONNX export friendly Tensorflow like 'SAME' convolution wrapper for 2D convolutions

    NOTE: This does not currently work with torch.jit.script
    """

    # pylint: disable=unused-argument
    def __init__(
            self,
            in_channels,
            out_channels,
            kernel_size,
            stride=1,
            padding=0,
            dilation=1,
            groups=1,
            bias=True,
    ):
        super(Conv2dSameExport, self).__init__(
            in_channels, out_channels, kernel_size,
            stride, 0, dilation, groups, bias,
        )
        self.pad = None
        self.pad_input_size = (0, 0)

    def forward(self, x):
        input_size = x.size()[-2:]
        if self.pad is None:
            pad_arg = pad_same_arg(input_size, self.weight.size()[-2:], self.stride, self.dilation)
            self.pad = nn.ZeroPad2d(pad_arg)
            self.pad_input_size = input_size

        x = self.pad(x)
        return F.conv2d(
            x, self.weight, self.bias,
            self.stride, self.padding, self.dilation, self.groups,
        )


def create_conv2d_pad(in_chs, out_chs, kernel_size, **kwargs):
    padding = kwargs.pop('padding', '')
    kwargs.setdefault('bias', False)
    padding, is_dynamic = get_padding_value(padding, kernel_size, **kwargs)
    if is_dynamic:
        if _USE_EXPORT_CONV and is_exportable():
            # older PyTorch ver needed this to export same padding reasonably
            assert not is_scriptable()  # Conv2DSameExport does not work with jit
            return Conv2dSameExport(in_chs, out_chs, kernel_size, **kwargs)
        else:
            return Conv2dSame(in_chs, out_chs, kernel_size, **kwargs)
    else:
        return nn.Conv2d(in_chs, out_chs, kernel_size, padding=padding, **kwargs)