# Copyright (c) OpenMMLab. All rights reserved.
import logging
from typing import List, Optional
import torch.nn as nn
import torch.nn.functional as F
from mmengine.logging import print_log
from torch import Tensor
from mmseg.registry import MODELS
from mmseg.utils import (ConfigType, OptConfigType, OptMultiConfig,
OptSampleList, SampleList, add_prefix)
from .base import BaseSegmentor
@MODELS.register_module()
class EncoderDecoder(BaseSegmentor):
"""Encoder Decoder segmentors.
EncoderDecoder typically consists of backbone, decode_head, auxiliary_head.
Note that auxiliary_head is only used for deep supervision during training,
which could be dumped during inference.
1. The ``loss`` method is used to calculate the loss of model,
which includes two steps: (1) Extracts features to obtain the feature maps
(2) Call the decode head loss function to forward decode head model and
calculate losses.
.. code:: text
loss(): extract_feat() -> _decode_head_forward_train() -> _auxiliary_head_forward_train (optional)
_decode_head_forward_train(): decode_head.loss()
_auxiliary_head_forward_train(): auxiliary_head.loss (optional)
2. The ``predict`` method is used to predict segmentation results,
which includes two steps: (1) Run inference function to obtain the list of
seg_logits (2) Call post-processing function to obtain list of
``SegDataSample`` including ``pred_sem_seg`` and ``seg_logits``.
.. code:: text
predict(): inference() -> postprocess_result()
infercen(): whole_inference()/slide_inference()
whole_inference()/slide_inference(): encoder_decoder()
encoder_decoder(): extract_feat() -> decode_head.predict()
3. The ``_forward`` method is used to output the tensor by running the model,
which includes two steps: (1) Extracts features to obtain the feature maps
(2)Call the decode head forward function to forward decode head model.
.. code:: text
_forward(): extract_feat() -> _decode_head.forward()
Args:
backbone (ConfigType): The config for the backnone of segmentor.
decode_head (ConfigType): The config for the decode head of segmentor.
neck (OptConfigType): The config for the neck of segmentor.
Defaults to None.
auxiliary_head (OptConfigType): The config for the auxiliary head of
segmentor. Defaults to None.
train_cfg (OptConfigType): The config for training. Defaults to None.
test_cfg (OptConfigType): The config for testing. Defaults to None.
data_preprocessor (dict, optional): The pre-process config of
:class:`BaseDataPreprocessor`.
pretrained (str, optional): The path for pretrained model.
Defaults to None.
init_cfg (dict, optional): The weight initialized config for
:class:`BaseModule`.
""" # noqa: E501
def __init__(self,
backbone: ConfigType,
decode_head: ConfigType,
neck: OptConfigType = None,
auxiliary_head: OptConfigType = None,
train_cfg: OptConfigType = None,
test_cfg: OptConfigType = None,
data_preprocessor: OptConfigType = None,
pretrained: Optional[str] = None,
init_cfg: OptMultiConfig = None):
super().__init__(
data_preprocessor=data_preprocessor, init_cfg=init_cfg)
if pretrained is not None:
assert backbone.get('pretrained') is None, \
'both backbone and segmentor set pretrained weight'
backbone.pretrained = pretrained
self.backbone = MODELS.build(backbone)
if neck is not None:
self.neck = MODELS.build(neck)
self._init_decode_head(decode_head)
self._init_auxiliary_head(auxiliary_head)
self.train_cfg = train_cfg
self.test_cfg = test_cfg
assert self.with_decode_head
def _init_decode_head(self, decode_head: ConfigType) -> None:
"""Initialize ``decode_head``"""
self.decode_head = MODELS.build(decode_head)
self.align_corners = self.decode_head.align_corners
self.num_classes = self.decode_head.num_classes
self.out_channels = self.decode_head.out_channels
def _init_auxiliary_head(self, auxiliary_head: ConfigType) -> None:
"""Initialize ``auxiliary_head``"""
if auxiliary_head is not None:
if isinstance(auxiliary_head, list):
self.auxiliary_head = nn.ModuleList()
for head_cfg in auxiliary_head:
self.auxiliary_head.append(MODELS.build(head_cfg))
else:
self.auxiliary_head = MODELS.build(auxiliary_head)
def extract_feat(self, inputs: Tensor) -> List[Tensor]:
"""Extract features from images."""
x = self.backbone(inputs)
if self.with_neck:
x = self.neck(x)
return x
def encode_decode(self, inputs: Tensor,
batch_img_metas: List[dict]) -> Tensor:
"""Encode images with backbone and decode into a semantic segmentation
map of the same size as input."""
x = self.extract_feat(inputs)
seg_logits = self.decode_head.predict(x, batch_img_metas,
self.test_cfg)
return seg_logits
def _decode_head_forward_train(self, inputs: List[Tensor],
data_samples: SampleList) -> dict:
"""Run forward function and calculate loss for decode head in
training."""
losses = dict()
loss_decode = self.decode_head.loss(inputs, data_samples,
self.train_cfg)
losses.update(add_prefix(loss_decode, 'decode'))
return losses
def _auxiliary_head_forward_train(self, inputs: List[Tensor],
data_samples: SampleList) -> dict:
"""Run forward function and calculate loss for auxiliary head in
training."""
losses = dict()
if isinstance(self.auxiliary_head, nn.ModuleList):
for idx, aux_head in enumerate(self.auxiliary_head):
loss_aux = aux_head.loss(inputs, data_samples, self.train_cfg)
losses.update(add_prefix(loss_aux, f'aux_{idx}'))
else:
loss_aux = self.auxiliary_head.loss(inputs, data_samples,
self.train_cfg)
losses.update(add_prefix(loss_aux, 'aux'))
return losses
def loss(self, inputs: Tensor, data_samples: SampleList) -> dict:
"""Calculate losses from a batch of inputs and data samples.
Args:
inputs (Tensor): Input images.
data_samples (list[:obj:`SegDataSample`]): The seg data samples.
It usually includes information such as `metainfo` and
`gt_sem_seg`.
Returns:
dict[str, Tensor]: a dictionary of loss components
"""
x = self.extract_feat(inputs)
losses = dict()
loss_decode = self._decode_head_forward_train(x, data_samples)
losses.update(loss_decode)
if self.with_auxiliary_head:
loss_aux = self._auxiliary_head_forward_train(x, data_samples)
losses.update(loss_aux)
return losses
def predict(self,
inputs: Tensor,
data_samples: OptSampleList = None) -> SampleList:
"""Predict results from a batch of inputs and data samples with post-
processing.
Args:
inputs (Tensor): Inputs with shape (N, C, H, W).
data_samples (List[:obj:`SegDataSample`], optional): The seg data
samples. It usually includes information such as `metainfo`
and `gt_sem_seg`.
Returns:
list[:obj:`SegDataSample`]: Segmentation results of the
input images. Each SegDataSample usually contain:
- ``pred_sem_seg``(PixelData): Prediction of semantic segmentation.
- ``seg_logits``(PixelData): Predicted logits of semantic
segmentation before normalization.
"""
if data_samples is not None:
batch_img_metas = [
data_sample.metainfo for data_sample in data_samples
]
else:
batch_img_metas = [
dict(
ori_shape=inputs.shape[2:],
img_shape=inputs.shape[2:],
pad_shape=inputs.shape[2:],
padding_size=[0, 0, 0, 0])
] * inputs.shape[0]
seg_logits = self.inference(inputs, batch_img_metas)
return self.postprocess_result(seg_logits, data_samples)
def _forward(self,
inputs: Tensor,
data_samples: OptSampleList = None) -> Tensor:
"""Network forward process.
Args:
inputs (Tensor): Inputs with shape (N, C, H, W).
data_samples (List[:obj:`SegDataSample`]): The seg
data samples. It usually includes information such
as `metainfo` and `gt_sem_seg`.
Returns:
Tensor: Forward output of model without any post-processes.
"""
x = self.extract_feat(inputs)
return self.decode_head.forward(x)
def slide_inference(self, inputs: Tensor,
batch_img_metas: List[dict]) -> Tensor:
"""Inference by sliding-window with overlap.
If h_crop > h_img or w_crop > w_img, the small patch will be used to
decode without padding.
Args:
inputs (tensor): the tensor should have a shape NxCxHxW,
which contains all images in the batch.
batch_img_metas (List[dict]): List of image metainfo where each may
also contain: 'img_shape', 'scale_factor', 'flip', 'img_path',
'ori_shape', and 'pad_shape'.
For details on the values of these keys see
`mmseg/datasets/pipelines/formatting.py:PackSegInputs`.
Returns:
Tensor: The segmentation results, seg_logits from model of each
input image.
"""
h_stride, w_stride = self.test_cfg.stride
h_crop, w_crop = self.test_cfg.crop_size
batch_size, _, h_img, w_img = inputs.size()
out_channels = self.out_channels
h_grids = max(h_img - h_crop + h_stride - 1, 0) // h_stride + 1
w_grids = max(w_img - w_crop + w_stride - 1, 0) // w_stride + 1
preds = inputs.new_zeros((batch_size, out_channels, h_img, w_img))
count_mat = inputs.new_zeros((batch_size, 1, h_img, w_img))
for h_idx in range(h_grids):
for w_idx in range(w_grids):
y1 = h_idx * h_stride
x1 = w_idx * w_stride
y2 = min(y1 + h_crop, h_img)
x2 = min(x1 + w_crop, w_img)
y1 = max(y2 - h_crop, 0)
x1 = max(x2 - w_crop, 0)
crop_img = inputs[:, :, y1:y2, x1:x2]
# change the image shape to patch shape
batch_img_metas[0]['img_shape'] = crop_img.shape[2:]
# the output of encode_decode is seg logits tensor map
# with shape [N, C, H, W]
crop_seg_logit = self.encode_decode(crop_img, batch_img_metas)
preds += F.pad(crop_seg_logit,
(int(x1), int(preds.shape[3] - x2), int(y1),
int(preds.shape[2] - y2)))
count_mat[:, :, y1:y2, x1:x2] += 1
assert (count_mat == 0).sum() == 0
seg_logits = preds / count_mat
return seg_logits
def whole_inference(self, inputs: Tensor,
batch_img_metas: List[dict]) -> Tensor:
"""Inference with full image.
Args:
inputs (Tensor): The tensor should have a shape NxCxHxW, which
contains all images in the batch.
batch_img_metas (List[dict]): List of image metainfo where each may
also contain: 'img_shape', 'scale_factor', 'flip', 'img_path',
'ori_shape', and 'pad_shape'.
For details on the values of these keys see
`mmseg/datasets/pipelines/formatting.py:PackSegInputs`.
Returns:
Tensor: The segmentation results, seg_logits from model of each
input image.
"""
seg_logits = self.encode_decode(inputs, batch_img_metas)
return seg_logits
def inference(self, inputs: Tensor, batch_img_metas: List[dict]) -> Tensor:
"""Inference with slide/whole style.
Args:
inputs (Tensor): The input image of shape (N, 3, H, W).
batch_img_metas (List[dict]): List of image metainfo where each may
also contain: 'img_shape', 'scale_factor', 'flip', 'img_path',
'ori_shape', 'pad_shape', and 'padding_size'.
For details on the values of these keys see
`mmseg/datasets/pipelines/formatting.py:PackSegInputs`.
Returns:
Tensor: The segmentation results, seg_logits from model of each
input image.
"""
assert self.test_cfg.get('mode', 'whole') in ['slide', 'whole'], \
f'Only "slide" or "whole" test mode are supported, but got ' \
f'{self.test_cfg["mode"]}.'
ori_shape = batch_img_metas[0]['ori_shape']
if not all(_['ori_shape'] == ori_shape for _ in batch_img_metas):
print_log(
'Image shapes are different in the batch.',
logger='current',
level=logging.WARN)
if self.test_cfg.mode == 'slide':
seg_logit = self.slide_inference(inputs, batch_img_metas)
else:
seg_logit = self.whole_inference(inputs, batch_img_metas)
return seg_logit
def aug_test(self, inputs, batch_img_metas, rescale=True):
"""Test with augmentations.
Only rescale=True is supported.
"""
# aug_test rescale all imgs back to ori_shape for now
assert rescale
# to save memory, we get augmented seg logit inplace
seg_logit = self.inference(inputs[0], batch_img_metas[0], rescale)
for i in range(1, len(inputs)):
cur_seg_logit = self.inference(inputs[i], batch_img_metas[i],
rescale)
seg_logit += cur_seg_logit
seg_logit /= len(inputs)
seg_pred = seg_logit.argmax(dim=1)
# unravel batch dim
seg_pred = list(seg_pred)
return seg_pred