# Source code for mmedit.models.losses.composition_loss

```
# Copyright (c) OpenMMLab. All rights reserved.
import torch.nn as nn
from ..registry import LOSSES
from .pixelwise_loss import charbonnier_loss, l1_loss, mse_loss
_reduction_modes = ['none', 'mean', 'sum']
[docs]@LOSSES.register_module()
class L1CompositionLoss(nn.Module):
"""L1 composition loss.
Args:
loss_weight (float): Loss weight for L1 loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
sample_wise (bool): Whether calculate the loss sample-wise. This
argument only takes effect when `reduction` is 'mean' and `weight`
(argument of `forward()`) is not None. It will first reduces loss
with 'mean' per-sample, and then it means over all the samples.
Default: False.
"""
def __init__(self, loss_weight=1.0, reduction='mean', sample_wise=False):
super().__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. '
f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
self.sample_wise = sample_wise
[docs] def forward(self, pred_alpha, fg, bg, ori_merged, weight=None, **kwargs):
"""
Args:
pred_alpha (Tensor): of shape (N, 1, H, W). Predicted alpha matte.
fg (Tensor): of shape (N, 3, H, W). Tensor of foreground object.
bg (Tensor): of shape (N, 3, H, W). Tensor of background object.
ori_merged (Tensor): of shape (N, 3, H, W). Tensor of origin merged
image before normalized by ImageNet mean and std.
weight (Tensor, optional): of shape (N, 1, H, W). It is an
indicating matrix: weight[trimap == 128] = 1. Default: None.
"""
pred_merged = pred_alpha * fg + (1. - pred_alpha) * bg
if weight is not None:
weight = weight.expand(-1, 3, -1, -1)
return self.loss_weight * l1_loss(
pred_merged,
ori_merged,
weight,
reduction=self.reduction,
sample_wise=self.sample_wise)
[docs]@LOSSES.register_module()
class MSECompositionLoss(nn.Module):
"""MSE (L2) composition loss.
Args:
loss_weight (float): Loss weight for MSE loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
sample_wise (bool): Whether calculate the loss sample-wise. This
argument only takes effect when `reduction` is 'mean' and `weight`
(argument of `forward()`) is not None. It will first reduces loss
with 'mean' per-sample, and then it means over all the samples.
Default: False.
"""
def __init__(self, loss_weight=1.0, reduction='mean', sample_wise=False):
super().__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. '
f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
self.sample_wise = sample_wise
[docs] def forward(self, pred_alpha, fg, bg, ori_merged, weight=None, **kwargs):
"""
Args:
pred_alpha (Tensor): of shape (N, 1, H, W). Predicted alpha matte.
fg (Tensor): of shape (N, 3, H, W). Tensor of foreground object.
bg (Tensor): of shape (N, 3, H, W). Tensor of background object.
ori_merged (Tensor): of shape (N, 3, H, W). Tensor of origin merged
image before normalized by ImageNet mean and std.
weight (Tensor, optional): of shape (N, 1, H, W). It is an
indicating matrix: weight[trimap == 128] = 1. Default: None.
"""
pred_merged = pred_alpha * fg + (1. - pred_alpha) * bg
if weight is not None:
weight = weight.expand(-1, 3, -1, -1)
return self.loss_weight * mse_loss(
pred_merged,
ori_merged,
weight,
reduction=self.reduction,
sample_wise=self.sample_wise)
[docs]@LOSSES.register_module()
class CharbonnierCompLoss(nn.Module):
"""Charbonnier composition loss.
Args:
loss_weight (float): Loss weight for L1 loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
sample_wise (bool): Whether calculate the loss sample-wise. This
argument only takes effect when `reduction` is 'mean' and `weight`
(argument of `forward()`) is not None. It will first reduces loss
with 'mean' per-sample, and then it means over all the samples.
Default: False.
eps (float): A value used to control the curvature near zero.
Default: 1e-12.
"""
def __init__(self,
loss_weight=1.0,
reduction='mean',
sample_wise=False,
eps=1e-12):
super().__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. '
f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
self.sample_wise = sample_wise
self.eps = eps
[docs] def forward(self, pred_alpha, fg, bg, ori_merged, weight=None, **kwargs):
"""
Args:
pred_alpha (Tensor): of shape (N, 1, H, W). Predicted alpha matte.
fg (Tensor): of shape (N, 3, H, W). Tensor of foreground object.
bg (Tensor): of shape (N, 3, H, W). Tensor of background object.
ori_merged (Tensor): of shape (N, 3, H, W). Tensor of origin merged
image before normalized by ImageNet mean and std.
weight (Tensor, optional): of shape (N, 1, H, W). It is an
indicating matrix: weight[trimap == 128] = 1. Default: None.
"""
pred_merged = pred_alpha * fg + (1. - pred_alpha) * bg
if weight is not None:
weight = weight.expand(-1, 3, -1, -1)
return self.loss_weight * charbonnier_loss(
pred_merged,
ori_merged,
weight,
eps=self.eps,
reduction=self.reduction,
sample_wise=self.sample_wise)
```