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# Copyright Niantic 2021. Patent Pending. All rights reserved.
#
# This software is licensed under the terms of the ManyDepth licence
# which allows for non-commercial use only, the full terms of which are made
# available in the LICENSE file.
import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
from collections import OrderedDict
class ConvBlock(nn.Module):
"""Layer to perform a convolution followed by ELU
"""
def __init__(self, in_channels, out_channels):
super(ConvBlock, self).__init__()
self.conv = Conv3x3(in_channels, out_channels)
self.nonlin = nn.ELU(inplace=True)
def forward(self, x):
out = self.conv(x)
out = self.nonlin(out)
return out
class Conv3x3(nn.Module):
"""Layer to pad and convolve input
"""
def __init__(self, in_channels, out_channels, use_refl=True):
super(Conv3x3, self).__init__()
if use_refl:
self.pad = nn.ReflectionPad2d(1)
else:
self.pad = nn.ZeroPad2d(1)
self.conv = nn.Conv2d(int(in_channels), int(out_channels), 3)
def forward(self, x):
out = self.pad(x)
out = self.conv(out)
return out
def upsample(x):
"""Upsample input tensor by a factor of 2
"""
return F.interpolate(x, scale_factor=2, mode="nearest")
class DepthDecoder(nn.Module):
def __init__(self, num_ch_enc, scales=range(4), num_output_channels=1, use_skips=True):
super(DepthDecoder, self).__init__()
self.num_output_channels = num_output_channels
self.use_skips = use_skips
self.upsample_mode = 'nearest'
self.scales = scales
self.num_ch_enc = num_ch_enc
self.num_ch_dec = np.array([16, 32, 64, 128, 256])
# decoder
self.convs = OrderedDict()
for i in range(4, -1, -1):
# upconv_0
num_ch_in = self.num_ch_enc[-1] if i == 4 else self.num_ch_dec[i + 1]
num_ch_out = self.num_ch_dec[i]
self.convs[("upconv", i, 0)] = ConvBlock(num_ch_in, num_ch_out)
# upconv_1
num_ch_in = self.num_ch_dec[i]
if self.use_skips and i > 0:
num_ch_in += self.num_ch_enc[i - 1]
num_ch_out = self.num_ch_dec[i]
self.convs[("upconv", i, 1)] = ConvBlock(num_ch_in, num_ch_out)
for s in self.scales:
self.convs[("dispconv", s)] = Conv3x3(self.num_ch_dec[s], self.num_output_channels)
self.decoder = nn.ModuleList(list(self.convs.values()))
self.sigmoid = nn.Sigmoid()
def forward(self, input_features):
self.outputs = {}
# decoder
x = input_features[-1]
for i in range(4, -1, -1):
x = self.convs[("upconv", i, 0)](x)
x = [upsample(x)]
if self.use_skips and i > 0:
x += [input_features[i - 1]]
x = torch.cat(x, 1)
x = self.convs[("upconv", i, 1)](x)
if i in self.scales:
self.outputs[("disp", i)] = self.sigmoid(self.convs[("dispconv", i)](x))
return self.outputs