import numpy as np
import torch
import torch.nn as nn
from mmcv.cnn import ConvModule
from mmcv.runner import force_fp32
from mmdet.core import (build_anchor_generator, build_assigner,
build_bbox_coder, build_sampler, images_to_levels,
multi_apply, multiclass_nms, unmap)
from ..builder import HEADS, build_loss
from .base_dense_head import BaseDenseHead
from .dense_test_mixins import BBoxTestMixin
from .guided_anchor_head import GuidedAnchorHead
[docs]@HEADS.register_module()
class SABLRetinaHead(BaseDenseHead, BBoxTestMixin):
"""Side-Aware Boundary Localization (SABL) for RetinaNet.
The anchor generation, assigning and sampling in SABLRetinaHead
are the same as GuidedAnchorHead for guided anchoring.
Please refer to https://arxiv.org/abs/1912.04260 for more details.
Args:
num_classes (int): Number of classes.
in_channels (int): Number of channels in the input feature map.
stacked_convs (int): Number of Convs for classification \
and regression branches. Defaults to 4.
feat_channels (int): Number of hidden channels. \
Defaults to 256.
approx_anchor_generator (dict): Config dict for approx generator.
square_anchor_generator (dict): Config dict for square generator.
conv_cfg (dict): Config dict for ConvModule. Defaults to None.
norm_cfg (dict): Config dict for Norm Layer. Defaults to None.
bbox_coder (dict): Config dict for bbox coder.
reg_decoded_bbox (bool): If true, the regression loss would be
applied directly on decoded bounding boxes, converting both
the predicted boxes and regression targets to absolute
coordinates format. Default False. It should be `True` when
using `IoULoss`, `GIoULoss`, or `DIoULoss` in the bbox head.
train_cfg (dict): Training config of SABLRetinaHead.
test_cfg (dict): Testing config of SABLRetinaHead.
loss_cls (dict): Config of classification loss.
loss_bbox_cls (dict): Config of classification loss for bbox branch.
loss_bbox_reg (dict): Config of regression loss for bbox branch.
init_cfg (dict or list[dict], optional): Initialization config dict.
"""
def __init__(self,
num_classes,
in_channels,
stacked_convs=4,
feat_channels=256,
approx_anchor_generator=dict(
type='AnchorGenerator',
octave_base_scale=4,
scales_per_octave=3,
ratios=[0.5, 1.0, 2.0],
strides=[8, 16, 32, 64, 128]),
square_anchor_generator=dict(
type='AnchorGenerator',
ratios=[1.0],
scales=[4],
strides=[8, 16, 32, 64, 128]),
conv_cfg=None,
norm_cfg=None,
bbox_coder=dict(
type='BucketingBBoxCoder',
num_buckets=14,
scale_factor=3.0),
reg_decoded_bbox=False,
train_cfg=None,
test_cfg=None,
loss_cls=dict(
type='FocalLoss',
use_sigmoid=True,
gamma=2.0,
alpha=0.25,
loss_weight=1.0),
loss_bbox_cls=dict(
type='CrossEntropyLoss',
use_sigmoid=True,
loss_weight=1.5),
loss_bbox_reg=dict(
type='SmoothL1Loss', beta=1.0 / 9.0, loss_weight=1.5),
init_cfg=dict(
type='Normal',
layer='Conv2d',
std=0.01,
override=dict(
type='Normal',
name='retina_cls',
std=0.01,
bias_prob=0.01))):
super(SABLRetinaHead, self).__init__(init_cfg)
self.in_channels = in_channels
self.num_classes = num_classes
self.feat_channels = feat_channels
self.num_buckets = bbox_coder['num_buckets']
self.side_num = int(np.ceil(self.num_buckets / 2))
assert (approx_anchor_generator['octave_base_scale'] ==
square_anchor_generator['scales'][0])
assert (approx_anchor_generator['strides'] ==
square_anchor_generator['strides'])
self.approx_anchor_generator = build_anchor_generator(
approx_anchor_generator)
self.square_anchor_generator = build_anchor_generator(
square_anchor_generator)
self.approxs_per_octave = (
self.approx_anchor_generator.num_base_anchors[0])
# one anchor per location
self.num_anchors = 1
self.stacked_convs = stacked_convs
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
self.reg_decoded_bbox = reg_decoded_bbox
self.use_sigmoid_cls = loss_cls.get('use_sigmoid', False)
self.sampling = loss_cls['type'] not in [
'FocalLoss', 'GHMC', 'QualityFocalLoss'
]
if self.use_sigmoid_cls:
self.cls_out_channels = num_classes
else:
self.cls_out_channels = num_classes + 1
self.bbox_coder = build_bbox_coder(bbox_coder)
self.loss_cls = build_loss(loss_cls)
self.loss_bbox_cls = build_loss(loss_bbox_cls)
self.loss_bbox_reg = build_loss(loss_bbox_reg)
self.train_cfg = train_cfg
self.test_cfg = test_cfg
if self.train_cfg:
self.assigner = build_assigner(self.train_cfg.assigner)
# use PseudoSampler when sampling is False
if self.sampling and hasattr(self.train_cfg, 'sampler'):
sampler_cfg = self.train_cfg.sampler
else:
sampler_cfg = dict(type='PseudoSampler')
self.sampler = build_sampler(sampler_cfg, context=self)
self.fp16_enabled = False
self._init_layers()
def _init_layers(self):
self.relu = nn.ReLU(inplace=True)
self.cls_convs = nn.ModuleList()
self.reg_convs = nn.ModuleList()
for i in range(self.stacked_convs):
chn = self.in_channels if i == 0 else self.feat_channels
self.cls_convs.append(
ConvModule(
chn,
self.feat_channels,
3,
stride=1,
padding=1,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg))
self.reg_convs.append(
ConvModule(
chn,
self.feat_channels,
3,
stride=1,
padding=1,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg))
self.retina_cls = nn.Conv2d(
self.feat_channels, self.cls_out_channels, 3, padding=1)
self.retina_bbox_reg = nn.Conv2d(
self.feat_channels, self.side_num * 4, 3, padding=1)
self.retina_bbox_cls = nn.Conv2d(
self.feat_channels, self.side_num * 4, 3, padding=1)
def forward_single(self, x):
cls_feat = x
reg_feat = x
for cls_conv in self.cls_convs:
cls_feat = cls_conv(cls_feat)
for reg_conv in self.reg_convs:
reg_feat = reg_conv(reg_feat)
cls_score = self.retina_cls(cls_feat)
bbox_cls_pred = self.retina_bbox_cls(reg_feat)
bbox_reg_pred = self.retina_bbox_reg(reg_feat)
bbox_pred = (bbox_cls_pred, bbox_reg_pred)
return cls_score, bbox_pred
[docs] def forward(self, feats):
return multi_apply(self.forward_single, feats)
[docs] def get_anchors(self, featmap_sizes, img_metas, device='cuda'):
"""Get squares according to feature map sizes and guided anchors.
Args:
featmap_sizes (list[tuple]): Multi-level feature map sizes.
img_metas (list[dict]): Image meta info.
device (torch.device | str): device for returned tensors
Returns:
tuple: square approxs of each image
"""
num_imgs = len(img_metas)
# since feature map sizes of all images are the same, we only compute
# squares for one time
multi_level_squares = self.square_anchor_generator.grid_anchors(
featmap_sizes, device=device)
squares_list = [multi_level_squares for _ in range(num_imgs)]
return squares_list
[docs] def get_target(self,
approx_list,
inside_flag_list,
square_list,
gt_bboxes_list,
img_metas,
gt_bboxes_ignore_list=None,
gt_labels_list=None,
label_channels=None,
sampling=True,
unmap_outputs=True):
"""Compute bucketing targets.
Args:
approx_list (list[list]): Multi level approxs of each image.
inside_flag_list (list[list]): Multi level inside flags of each
image.
square_list (list[list]): Multi level squares of each image.
gt_bboxes_list (list[Tensor]): Ground truth bboxes of each image.
img_metas (list[dict]): Meta info of each image.
gt_bboxes_ignore_list (list[Tensor]): ignore list of gt bboxes.
gt_bboxes_list (list[Tensor]): Gt bboxes of each image.
label_channels (int): Channel of label.
sampling (bool): Sample Anchors or not.
unmap_outputs (bool): unmap outputs or not.
Returns:
tuple: Returns a tuple containing learning targets.
- labels_list (list[Tensor]): Labels of each level.
- label_weights_list (list[Tensor]): Label weights of each \
level.
- bbox_cls_targets_list (list[Tensor]): BBox cls targets of \
each level.
- bbox_cls_weights_list (list[Tensor]): BBox cls weights of \
each level.
- bbox_reg_targets_list (list[Tensor]): BBox reg targets of \
each level.
- bbox_reg_weights_list (list[Tensor]): BBox reg weights of \
each level.
- num_total_pos (int): Number of positive samples in all \
images.
- num_total_neg (int): Number of negative samples in all \
images.
"""
num_imgs = len(img_metas)
assert len(approx_list) == len(inside_flag_list) == len(
square_list) == num_imgs
# anchor number of multi levels
num_level_squares = [squares.size(0) for squares in square_list[0]]
# concat all level anchors and flags to a single tensor
inside_flag_flat_list = []
approx_flat_list = []
square_flat_list = []
for i in range(num_imgs):
assert len(square_list[i]) == len(inside_flag_list[i])
inside_flag_flat_list.append(torch.cat(inside_flag_list[i]))
approx_flat_list.append(torch.cat(approx_list[i]))
square_flat_list.append(torch.cat(square_list[i]))
# compute targets for each image
if gt_bboxes_ignore_list is None:
gt_bboxes_ignore_list = [None for _ in range(num_imgs)]
if gt_labels_list is None:
gt_labels_list = [None for _ in range(num_imgs)]
(all_labels, all_label_weights, all_bbox_cls_targets,
all_bbox_cls_weights, all_bbox_reg_targets, all_bbox_reg_weights,
pos_inds_list, neg_inds_list) = multi_apply(
self._get_target_single,
approx_flat_list,
inside_flag_flat_list,
square_flat_list,
gt_bboxes_list,
gt_bboxes_ignore_list,
gt_labels_list,
img_metas,
label_channels=label_channels,
sampling=sampling,
unmap_outputs=unmap_outputs)
# no valid anchors
if any([labels is None for labels in all_labels]):
return None
# sampled anchors of all images
num_total_pos = sum([max(inds.numel(), 1) for inds in pos_inds_list])
num_total_neg = sum([max(inds.numel(), 1) for inds in neg_inds_list])
# split targets to a list w.r.t. multiple levels
labels_list = images_to_levels(all_labels, num_level_squares)
label_weights_list = images_to_levels(all_label_weights,
num_level_squares)
bbox_cls_targets_list = images_to_levels(all_bbox_cls_targets,
num_level_squares)
bbox_cls_weights_list = images_to_levels(all_bbox_cls_weights,
num_level_squares)
bbox_reg_targets_list = images_to_levels(all_bbox_reg_targets,
num_level_squares)
bbox_reg_weights_list = images_to_levels(all_bbox_reg_weights,
num_level_squares)
return (labels_list, label_weights_list, bbox_cls_targets_list,
bbox_cls_weights_list, bbox_reg_targets_list,
bbox_reg_weights_list, num_total_pos, num_total_neg)
def _get_target_single(self,
flat_approxs,
inside_flags,
flat_squares,
gt_bboxes,
gt_bboxes_ignore,
gt_labels,
img_meta,
label_channels=None,
sampling=True,
unmap_outputs=True):
"""Compute regression and classification targets for anchors in a
single image.
Args:
flat_approxs (Tensor): flat approxs of a single image,
shape (n, 4)
inside_flags (Tensor): inside flags of a single image,
shape (n, ).
flat_squares (Tensor): flat squares of a single image,
shape (approxs_per_octave * n, 4)
gt_bboxes (Tensor): Ground truth bboxes of a single image, \
shape (num_gts, 4).
gt_bboxes_ignore (Tensor): Ground truth bboxes to be
ignored, shape (num_ignored_gts, 4).
gt_labels (Tensor): Ground truth labels of each box,
shape (num_gts,).
img_meta (dict): Meta info of the image.
label_channels (int): Channel of label.
sampling (bool): Sample Anchors or not.
unmap_outputs (bool): unmap outputs or not.
Returns:
tuple:
- labels_list (Tensor): Labels in a single image
- label_weights (Tensor): Label weights in a single image
- bbox_cls_targets (Tensor): BBox cls targets in a single image
- bbox_cls_weights (Tensor): BBox cls weights in a single image
- bbox_reg_targets (Tensor): BBox reg targets in a single image
- bbox_reg_weights (Tensor): BBox reg weights in a single image
- num_total_pos (int): Number of positive samples \
in a single image
- num_total_neg (int): Number of negative samples \
in a single image
"""
if not inside_flags.any():
return (None, ) * 8
# assign gt and sample anchors
expand_inside_flags = inside_flags[:, None].expand(
-1, self.approxs_per_octave).reshape(-1)
approxs = flat_approxs[expand_inside_flags, :]
squares = flat_squares[inside_flags, :]
assign_result = self.assigner.assign(approxs, squares,
self.approxs_per_octave,
gt_bboxes, gt_bboxes_ignore)
sampling_result = self.sampler.sample(assign_result, squares,
gt_bboxes)
num_valid_squares = squares.shape[0]
bbox_cls_targets = squares.new_zeros(
(num_valid_squares, self.side_num * 4))
bbox_cls_weights = squares.new_zeros(
(num_valid_squares, self.side_num * 4))
bbox_reg_targets = squares.new_zeros(
(num_valid_squares, self.side_num * 4))
bbox_reg_weights = squares.new_zeros(
(num_valid_squares, self.side_num * 4))
labels = squares.new_full((num_valid_squares, ),
self.num_classes,
dtype=torch.long)
label_weights = squares.new_zeros(num_valid_squares, dtype=torch.float)
pos_inds = sampling_result.pos_inds
neg_inds = sampling_result.neg_inds
if len(pos_inds) > 0:
(pos_bbox_reg_targets, pos_bbox_reg_weights, pos_bbox_cls_targets,
pos_bbox_cls_weights) = self.bbox_coder.encode(
sampling_result.pos_bboxes, sampling_result.pos_gt_bboxes)
bbox_cls_targets[pos_inds, :] = pos_bbox_cls_targets
bbox_reg_targets[pos_inds, :] = pos_bbox_reg_targets
bbox_cls_weights[pos_inds, :] = pos_bbox_cls_weights
bbox_reg_weights[pos_inds, :] = pos_bbox_reg_weights
if gt_labels is None:
# Only rpn gives gt_labels as None
# Foreground is the first class
labels[pos_inds] = 0
else:
labels[pos_inds] = gt_labels[
sampling_result.pos_assigned_gt_inds]
if self.train_cfg.pos_weight <= 0:
label_weights[pos_inds] = 1.0
else:
label_weights[pos_inds] = self.train_cfg.pos_weight
if len(neg_inds) > 0:
label_weights[neg_inds] = 1.0
# map up to original set of anchors
if unmap_outputs:
num_total_anchors = flat_squares.size(0)
labels = unmap(
labels, num_total_anchors, inside_flags, fill=self.num_classes)
label_weights = unmap(label_weights, num_total_anchors,
inside_flags)
bbox_cls_targets = unmap(bbox_cls_targets, num_total_anchors,
inside_flags)
bbox_cls_weights = unmap(bbox_cls_weights, num_total_anchors,
inside_flags)
bbox_reg_targets = unmap(bbox_reg_targets, num_total_anchors,
inside_flags)
bbox_reg_weights = unmap(bbox_reg_weights, num_total_anchors,
inside_flags)
return (labels, label_weights, bbox_cls_targets, bbox_cls_weights,
bbox_reg_targets, bbox_reg_weights, pos_inds, neg_inds)
def loss_single(self, cls_score, bbox_pred, labels, label_weights,
bbox_cls_targets, bbox_cls_weights, bbox_reg_targets,
bbox_reg_weights, num_total_samples):
# classification loss
labels = labels.reshape(-1)
label_weights = label_weights.reshape(-1)
cls_score = cls_score.permute(0, 2, 3,
1).reshape(-1, self.cls_out_channels)
loss_cls = self.loss_cls(
cls_score, labels, label_weights, avg_factor=num_total_samples)
# regression loss
bbox_cls_targets = bbox_cls_targets.reshape(-1, self.side_num * 4)
bbox_cls_weights = bbox_cls_weights.reshape(-1, self.side_num * 4)
bbox_reg_targets = bbox_reg_targets.reshape(-1, self.side_num * 4)
bbox_reg_weights = bbox_reg_weights.reshape(-1, self.side_num * 4)
(bbox_cls_pred, bbox_reg_pred) = bbox_pred
bbox_cls_pred = bbox_cls_pred.permute(0, 2, 3, 1).reshape(
-1, self.side_num * 4)
bbox_reg_pred = bbox_reg_pred.permute(0, 2, 3, 1).reshape(
-1, self.side_num * 4)
loss_bbox_cls = self.loss_bbox_cls(
bbox_cls_pred,
bbox_cls_targets.long(),
bbox_cls_weights,
avg_factor=num_total_samples * 4 * self.side_num)
loss_bbox_reg = self.loss_bbox_reg(
bbox_reg_pred,
bbox_reg_targets,
bbox_reg_weights,
avg_factor=num_total_samples * 4 * self.bbox_coder.offset_topk)
return loss_cls, loss_bbox_cls, loss_bbox_reg
[docs] @force_fp32(apply_to=('cls_scores', 'bbox_preds'))
def loss(self,
cls_scores,
bbox_preds,
gt_bboxes,
gt_labels,
img_metas,
gt_bboxes_ignore=None):
featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores]
assert len(featmap_sizes) == self.approx_anchor_generator.num_levels
device = cls_scores[0].device
# get sampled approxes
approxs_list, inside_flag_list = GuidedAnchorHead.get_sampled_approxs(
self, featmap_sizes, img_metas, device=device)
square_list = self.get_anchors(featmap_sizes, img_metas, device=device)
label_channels = self.cls_out_channels if self.use_sigmoid_cls else 1
cls_reg_targets = self.get_target(
approxs_list,
inside_flag_list,
square_list,
gt_bboxes,
img_metas,
gt_bboxes_ignore_list=gt_bboxes_ignore,
gt_labels_list=gt_labels,
label_channels=label_channels,
sampling=self.sampling)
if cls_reg_targets is None:
return None
(labels_list, label_weights_list, bbox_cls_targets_list,
bbox_cls_weights_list, bbox_reg_targets_list, bbox_reg_weights_list,
num_total_pos, num_total_neg) = cls_reg_targets
num_total_samples = (
num_total_pos + num_total_neg if self.sampling else num_total_pos)
losses_cls, losses_bbox_cls, losses_bbox_reg = multi_apply(
self.loss_single,
cls_scores,
bbox_preds,
labels_list,
label_weights_list,
bbox_cls_targets_list,
bbox_cls_weights_list,
bbox_reg_targets_list,
bbox_reg_weights_list,
num_total_samples=num_total_samples)
return dict(
loss_cls=losses_cls,
loss_bbox_cls=losses_bbox_cls,
loss_bbox_reg=losses_bbox_reg)
[docs] @force_fp32(apply_to=('cls_scores', 'bbox_preds'))
def get_bboxes(self,
cls_scores,
bbox_preds,
img_metas,
cfg=None,
rescale=False):
assert len(cls_scores) == len(bbox_preds)
num_levels = len(cls_scores)
featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores]
device = cls_scores[0].device
mlvl_anchors = self.get_anchors(
featmap_sizes, img_metas, device=device)
result_list = []
for img_id in range(len(img_metas)):
cls_score_list = [
cls_scores[i][img_id].detach() for i in range(num_levels)
]
bbox_cls_pred_list = [
bbox_preds[i][0][img_id].detach() for i in range(num_levels)
]
bbox_reg_pred_list = [
bbox_preds[i][1][img_id].detach() for i in range(num_levels)
]
img_shape = img_metas[img_id]['img_shape']
scale_factor = img_metas[img_id]['scale_factor']
proposals = self.get_bboxes_single(cls_score_list,
bbox_cls_pred_list,
bbox_reg_pred_list,
mlvl_anchors[img_id], img_shape,
scale_factor, cfg, rescale)
result_list.append(proposals)
return result_list
def get_bboxes_single(self,
cls_scores,
bbox_cls_preds,
bbox_reg_preds,
mlvl_anchors,
img_shape,
scale_factor,
cfg,
rescale=False):
cfg = self.test_cfg if cfg is None else cfg
mlvl_bboxes = []
mlvl_scores = []
mlvl_confids = []
assert len(cls_scores) == len(bbox_cls_preds) == len(
bbox_reg_preds) == len(mlvl_anchors)
for cls_score, bbox_cls_pred, bbox_reg_pred, anchors in zip(
cls_scores, bbox_cls_preds, bbox_reg_preds, mlvl_anchors):
assert cls_score.size()[-2:] == bbox_cls_pred.size(
)[-2:] == bbox_reg_pred.size()[-2::]
cls_score = cls_score.permute(1, 2,
0).reshape(-1, self.cls_out_channels)
if self.use_sigmoid_cls:
scores = cls_score.sigmoid()
else:
scores = cls_score.softmax(-1)
bbox_cls_pred = bbox_cls_pred.permute(1, 2, 0).reshape(
-1, self.side_num * 4)
bbox_reg_pred = bbox_reg_pred.permute(1, 2, 0).reshape(
-1, self.side_num * 4)
nms_pre = cfg.get('nms_pre', -1)
if nms_pre > 0 and scores.shape[0] > nms_pre:
if self.use_sigmoid_cls:
max_scores, _ = scores.max(dim=1)
else:
max_scores, _ = scores[:, :-1].max(dim=1)
_, topk_inds = max_scores.topk(nms_pre)
anchors = anchors[topk_inds, :]
bbox_cls_pred = bbox_cls_pred[topk_inds, :]
bbox_reg_pred = bbox_reg_pred[topk_inds, :]
scores = scores[topk_inds, :]
bbox_preds = [
bbox_cls_pred.contiguous(),
bbox_reg_pred.contiguous()
]
bboxes, confids = self.bbox_coder.decode(
anchors.contiguous(), bbox_preds, max_shape=img_shape)
mlvl_bboxes.append(bboxes)
mlvl_scores.append(scores)
mlvl_confids.append(confids)
mlvl_bboxes = torch.cat(mlvl_bboxes)
if rescale:
mlvl_bboxes /= mlvl_bboxes.new_tensor(scale_factor)
mlvl_scores = torch.cat(mlvl_scores)
mlvl_confids = torch.cat(mlvl_confids)
if self.use_sigmoid_cls:
padding = mlvl_scores.new_zeros(mlvl_scores.shape[0], 1)
mlvl_scores = torch.cat([mlvl_scores, padding], dim=1)
det_bboxes, det_labels = multiclass_nms(
mlvl_bboxes,
mlvl_scores,
cfg.score_thr,
cfg.nms,
cfg.max_per_img,
score_factors=mlvl_confids)
return det_bboxes, det_labels