models/backbone/common.py

import torch
import torch.nn as nn
import numpy as np
from .downsampler import Downsampler


def add_module(self, module):
    self.add_module(str(len(self) + 1), module)


torch.nn.Module.add = add_module


class Concat(nn.Module):
    def __init__(self, dim, *args):
        super(Concat, self).__init__()
        self.dim = dim

        for idx, module in enumerate(args):
            self.add_module(str(idx), module)

    def forward(self, input):
        inputs = []
        for module in self._modules.values():
            inputs.append(module(input))

        inputs_shapes2 = [x.shape[2] for x in inputs]
        inputs_shapes3 = [x.shape[3] for x in inputs]

        if np.all(np.array(inputs_shapes2) == min(inputs_shapes2)) and np.all(
            np.array(inputs_shapes3) == min(inputs_shapes3)
        ):
            inputs_ = inputs
        else:
            target_shape2 = min(inputs_shapes2)
            target_shape3 = min(inputs_shapes3)

            inputs_ = []
            for inp in inputs:
                diff2 = (inp.size(2) - target_shape2) // 2
                diff3 = (inp.size(3) - target_shape3) // 2
                inputs_.append(inp[:, :, diff2 : diff2 + target_shape2, diff3 : diff3 + target_shape3])

        return torch.cat(inputs_, dim=self.dim)

    def __len__(self):
        return len(self._modules)


class GenNoise(nn.Module):
    def __init__(self, dim2):
        super(GenNoise, self).__init__()
        self.dim2 = dim2

    def forward(self, input):
        a = list(input.size())
        a[1] = self.dim2
        # print (input.data.type())

        b = torch.zeros(a).type_as(input.data)
        b.normal_()

        x = torch.autograd.Variable(b)

        return x


class Swish(nn.Module):
    """
    https://arxiv.org/abs/1710.05941
    The hype was so huge that I could not help but try it
    """

    def __init__(self):
        super(Swish, self).__init__()
        self.s = nn.Sigmoid()

    def forward(self, x):
        return x * self.s(x)


def act(act_fun="LeakyReLU"):
    """
    Either string defining an activation function or module (e.g. nn.ReLU)
    """
    if isinstance(act_fun, str):
        if act_fun == "LeakyReLU":
            return nn.LeakyReLU(0.2, inplace=True)
        elif act_fun == "Swish":
            return Swish()
        elif act_fun == "ELU":
            return nn.ELU()
        elif act_fun == "none":
            return nn.Sequential()
        else:
            assert False
    else:
        return act_fun()


class PixelNormLayer(nn.Module):
    """
    Pixelwise feature vector normalization.
    """

    def __init__(self, eps=1e-8):
        super(PixelNormLayer, self).__init__()
        self.eps = eps

    def forward(self, x):
        return x / torch.sqrt(torch.mean(x ** 2, dim=1, keepdim=True) + 1e-8)

    def __repr__(self):
        return self.__class__.__name__ + "(eps = %s)" % (self.eps)


def pixelnorm(num_features):
    return PixelNormLayer()


def bn(num_features):
    return nn.BatchNorm2d(num_features)


def conv(in_f, out_f, kernel_size, stride=1, bias=True, pad="zero", downsample_mode="stride"):
    downsampler = None
    if stride != 1 and downsample_mode != "stride":

        if downsample_mode == "avg":
            downsampler = nn.AvgPool2d(stride, stride)
        elif downsample_mode == "max":
            downsampler = nn.MaxPool2d(stride, stride)
        elif downsample_mode in ["lanczos2", "lanczos3"]:
            downsampler = Downsampler(
                n_planes=out_f, factor=stride, kernel_type=downsample_mode, phase=0.5, preserve_size=True
            )
        else:
            assert False

        stride = 1

    padder = None
    to_pad = int((kernel_size - 1) / 2)
    if pad == "reflection":
        padder = nn.ReflectionPad2d(to_pad)
        to_pad = 0

    convolver = nn.Conv2d(in_f, out_f, kernel_size, stride, padding=to_pad, bias=bias)

    layers = filter(lambda x: x is not None, [padder, convolver, downsampler])
    return nn.Sequential(*layers)


class DecorrelatedColorsToRGB(nn.Module):
    """Converts from a decorrelated color space to RGB. See
    https://github.com/eps696/aphantasia/blob/master/aphantasia/image.py. Usually intended
    to be followed by a sigmoid.
    """

    def __init__(self, inv_color_scale=1.6):
        super().__init__()
        color_correlation_svd_sqrt = torch.tensor([[0.26, 0.09, 0.02], [0.27, 0.00, -0.05], [0.27, -0.09, 0.03]])
        color_correlation_svd_sqrt /= torch.tensor([inv_color_scale, 1.0, 1.0])  # saturate, empirical
        max_norm_svd_sqrt = color_correlation_svd_sqrt.norm(dim=0).max()
        color_correlation_normalized = color_correlation_svd_sqrt / max_norm_svd_sqrt
        self.register_buffer("colcorr_t", color_correlation_normalized.T)

    def inverse(self, image):
        colcorr_t_inv = torch.linalg.inv(self.colcorr_t)
        return torch.einsum("nchw,cd->ndhw", image, colcorr_t_inv)

    def forward(self, image):
        if image.dim() == 4:
            image_rgb, alpha = image[:, :3], image[:, 3].unsqueeze(1)
            image_rgb = torch.einsum("nchw,cd->ndhw", image_rgb, self.colcorr_t)
            image = torch.cat([image_rgb, alpha], dim=1)
        else:
            image = torch.einsum("nchw,cd->ndhw", image, self.colcorr_t)
        return image