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import torch
from ..inference import RPNPostProcessor
from ..utils import permute_and_flatten
from maskrcnn_benchmark.modeling.box_coder import BoxCoder
from maskrcnn_benchmark.modeling.utils import cat
from maskrcnn_benchmark.structures.bounding_box import BoxList
from maskrcnn_benchmark.structures.boxlist_ops import cat_boxlist
from maskrcnn_benchmark.structures.boxlist_ops import boxlist_nms
from maskrcnn_benchmark.structures.boxlist_ops import remove_small_boxes
class RetinaNetPostProcessor(RPNPostProcessor):
"""
Performs post-processing on the outputs of the RetinaNet boxes.
This is only used in the testing.
"""
def __init__(
self,
pre_nms_thresh,
pre_nms_top_n,
nms_thresh,
fpn_post_nms_top_n,
min_size,
num_classes,
box_coder=None,
):
"""
Arguments:
pre_nms_thresh (float)
pre_nms_top_n (int)
nms_thresh (float)
fpn_post_nms_top_n (int)
min_size (int)
num_classes (int)
box_coder (BoxCoder)
"""
super(RetinaNetPostProcessor, self).__init__(
pre_nms_thresh, 0, nms_thresh, min_size
)
self.pre_nms_thresh = pre_nms_thresh
self.pre_nms_top_n = pre_nms_top_n
self.nms_thresh = nms_thresh
self.fpn_post_nms_top_n = fpn_post_nms_top_n
self.min_size = min_size
self.num_classes = num_classes
if box_coder is None:
box_coder = BoxCoder(weights=(10., 10., 5., 5.))
self.box_coder = box_coder
def add_gt_proposals(self, proposals, targets):
"""
This function is not used in RetinaNet
"""
pass
def forward_for_single_feature_map(
self, anchors, box_cls, box_regression):
"""
Arguments:
anchors: list[BoxList]
box_cls: tensor of size N, A * C, H, W
box_regression: tensor of size N, A * 4, H, W
"""
device = box_cls.device
N, _, H, W = box_cls.shape
A = box_regression.size(1) // 4
C = box_cls.size(1) // A
# put in the same format as anchors
box_cls = permute_and_flatten(box_cls, N, A, C, H, W)
box_cls = box_cls.sigmoid()
box_regression = permute_and_flatten(box_regression, N, A, 4, H, W)
box_regression = box_regression.reshape(N, -1, 4)
num_anchors = A * H * W
candidate_inds = box_cls > self.pre_nms_thresh
pre_nms_top_n = candidate_inds.view(N, -1).sum(1)
pre_nms_top_n = pre_nms_top_n.clamp(max=self.pre_nms_top_n)
results = []
for per_box_cls, per_box_regression, per_pre_nms_top_n, \
per_candidate_inds, per_anchors in zip(
box_cls,
box_regression,
pre_nms_top_n,
candidate_inds,
anchors):
# Sort and select TopN
# TODO most of this can be made out of the loop for
# all images.
# TODO:Yang: Not easy to do. Because the numbers of detections are
# different in each image. Therefore, this part needs to be done
# per image.
per_box_cls = per_box_cls[per_candidate_inds]
per_box_cls, top_k_indices = \
per_box_cls.topk(per_pre_nms_top_n, sorted=False)
per_candidate_nonzeros = \
per_candidate_inds.nonzero()[top_k_indices, :]
per_box_loc = per_candidate_nonzeros[:, 0]
per_class = per_candidate_nonzeros[:, 1]
per_class += 1
detections = self.box_coder.decode(
per_box_regression[per_box_loc, :].view(-1, 4),
per_anchors.bbox[per_box_loc, :].view(-1, 4)
)
boxlist = BoxList(detections, per_anchors.size, mode="xyxy")
boxlist.add_field("labels", per_class)
boxlist.add_field("scores", per_box_cls)
boxlist = boxlist.clip_to_image(remove_empty=False)
boxlist = remove_small_boxes(boxlist, self.min_size)
results.append(boxlist)
return results
# TODO very similar to filter_results from PostProcessor
# but filter_results is per image
# TODO Yang: solve this issue in the future. No good solution
# right now.
def select_over_all_levels(self, boxlists):
num_images = len(boxlists)
results = []
for i in range(num_images):
scores = boxlists[i].get_field("scores")
labels = boxlists[i].get_field("labels")
boxes = boxlists[i].bbox
boxlist = boxlists[i]
result = []
# skip the background
for j in range(1, self.num_classes):
inds = (labels == j).nonzero().view(-1)
scores_j = scores[inds]
boxes_j = boxes[inds, :].view(-1, 4)
boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
boxlist_for_class.add_field("scores", scores_j)
boxlist_for_class = boxlist_nms(
boxlist_for_class, self.nms_thresh,
score_field="scores"
)
num_labels = len(boxlist_for_class)
boxlist_for_class.add_field(
"labels", torch.full((num_labels,), j,
dtype=torch.int64,
device=scores.device)
)
result.append(boxlist_for_class)
result = cat_boxlist(result)
number_of_detections = len(result)
# Limit to max_per_image detections **over all classes**
if number_of_detections > self.fpn_post_nms_top_n > 0:
cls_scores = result.get_field("scores")
image_thresh, _ = torch.kthvalue(
cls_scores.cpu(),
number_of_detections - self.fpn_post_nms_top_n + 1
)
keep = cls_scores >= image_thresh.item()
keep = torch.nonzero(keep).squeeze(1)
result = result[keep]
results.append(result)
return results
def make_retinanet_postprocessor(config, rpn_box_coder, is_train):
pre_nms_thresh = config.MODEL.RETINANET.INFERENCE_TH
pre_nms_top_n = config.MODEL.RETINANET.PRE_NMS_TOP_N
nms_thresh = config.MODEL.RETINANET.NMS_TH
fpn_post_nms_top_n = config.TEST.DETECTIONS_PER_IMG
min_size = 0
box_selector = RetinaNetPostProcessor(
pre_nms_thresh=pre_nms_thresh,
pre_nms_top_n=pre_nms_top_n,
nms_thresh=nms_thresh,
fpn_post_nms_top_n=fpn_post_nms_top_n,
min_size=min_size,
num_classes=config.MODEL.RETINANET.NUM_CLASSES,
box_coder=rpn_box_coder,
)
return box_selector
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