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# Copyright 2023 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Contains definitions of ROI generator."""
from typing import Optional, Mapping
# Import libraries
import tensorflow as tf, tf_keras
from official.vision.ops import box_ops
from official.vision.ops import nms
def _multilevel_propose_rois(raw_boxes: Mapping[str, tf.Tensor],
raw_scores: Mapping[str, tf.Tensor],
anchor_boxes: Mapping[str, tf.Tensor],
image_shape: tf.Tensor,
pre_nms_top_k: int = 2000,
pre_nms_score_threshold: float = 0.0,
pre_nms_min_size_threshold: float = 0.0,
nms_iou_threshold: float = 0.7,
num_proposals: int = 1000,
use_batched_nms: bool = False,
decode_boxes: bool = True,
clip_boxes: bool = True,
apply_sigmoid_to_score: bool = True):
"""Proposes RoIs given a group of candidates from different FPN levels.
The following describes the steps:
1. For each individual level:
a. Apply sigmoid transform if specified.
b. Decode boxes if specified.
c. Clip boxes if specified.
d. Filter small boxes and those fall outside image if specified.
e. Apply pre-NMS filtering including pre-NMS top k and score thresholding.
f. Apply NMS.
2. Aggregate post-NMS boxes from each level.
3. Apply an overall top k to generate the final selected RoIs.
Args:
raw_boxes: A `dict` with keys representing FPN levels and values
representing box tenors of shape
[batch_size, feature_h, feature_w, num_anchors * 4].
raw_scores: A `dict` with keys representing FPN levels and values
representing logit tensors of shape
[batch_size, feature_h, feature_w, num_anchors].
anchor_boxes: A `dict` with keys representing FPN levels and values
representing anchor box tensors of shape
[batch_size, feature_h * feature_w * num_anchors, 4].
image_shape: A `tf.Tensor` of shape [batch_size, 2] where the last dimension
are [height, width] of the scaled image.
pre_nms_top_k: An `int` of top scoring RPN proposals *per level* to keep
before applying NMS. Default: 2000.
pre_nms_score_threshold: A `float` between 0 and 1 representing the minimal
box score to keep before applying NMS. This is often used as a
pre-filtering step for better performance. Default: 0, no filtering is
applied.
pre_nms_min_size_threshold: A `float` representing the minimal box size in
each side (w.r.t. the scaled image) to keep before applying NMS. This is
often used as a pre-filtering step for better performance. Default: 0, no
filtering is applied.
nms_iou_threshold: A `float` between 0 and 1 representing the IoU threshold
used for NMS. If 0.0, no NMS is applied. Default: 0.7.
num_proposals: An `int` of top scoring RPN proposals *in total* to keep
after applying NMS. Default: 1000.
use_batched_nms: A `bool` indicating whether NMS is applied in batch using
`tf.image.combined_non_max_suppression`. Currently only available in
CPU/GPU. Default is False.
decode_boxes: A `bool` indicating whether `raw_boxes` needs to be decoded
using `anchor_boxes`. If False, use `raw_boxes` directly and ignore
`anchor_boxes`. Default is True.
clip_boxes: A `bool` indicating whether boxes are first clipped to the
scaled image size before appliying NMS. If False, no clipping is applied
and `image_shape` is ignored. Default is True.
apply_sigmoid_to_score: A `bool` indicating whether apply sigmoid to
`raw_scores` before applying NMS. Default is True.
Returns:
selected_rois: A `tf.Tensor` of shape [batch_size, num_proposals, 4],
representing the box coordinates of the selected proposals w.r.t. the
scaled image.
selected_roi_scores: A `tf.Tensor` of shape [batch_size, num_proposals, 1],
representing the scores of the selected proposals.
"""
with tf.name_scope('multilevel_propose_rois'):
rois = []
roi_scores = []
image_shape = tf.expand_dims(image_shape, axis=1)
for level in sorted(raw_scores.keys()):
with tf.name_scope('level_%s' % level):
_, feature_h, feature_w, num_anchors_per_location = (
raw_scores[level].get_shape().as_list())
num_boxes = feature_h * feature_w * num_anchors_per_location
this_level_scores = tf.reshape(raw_scores[level], [-1, num_boxes])
this_level_boxes = tf.reshape(raw_boxes[level], [-1, num_boxes, 4])
this_level_anchors = tf.cast(
tf.reshape(anchor_boxes[level], [-1, num_boxes, 4]),
dtype=this_level_scores.dtype)
if apply_sigmoid_to_score:
this_level_scores = tf.sigmoid(this_level_scores)
if decode_boxes:
this_level_boxes = box_ops.decode_boxes(
this_level_boxes, this_level_anchors)
if clip_boxes:
this_level_boxes = box_ops.clip_boxes(
this_level_boxes, image_shape)
if pre_nms_min_size_threshold > 0.0:
this_level_boxes, this_level_scores = box_ops.filter_boxes(
this_level_boxes,
this_level_scores,
image_shape,
pre_nms_min_size_threshold)
this_level_pre_nms_top_k = min(num_boxes, pre_nms_top_k)
this_level_post_nms_top_k = min(num_boxes, num_proposals)
if nms_iou_threshold > 0.0:
if use_batched_nms:
this_level_rois, this_level_roi_scores, _, _ = (
tf.image.combined_non_max_suppression(
tf.expand_dims(this_level_boxes, axis=2),
tf.expand_dims(this_level_scores, axis=-1),
max_output_size_per_class=this_level_pre_nms_top_k,
max_total_size=this_level_post_nms_top_k,
iou_threshold=nms_iou_threshold,
score_threshold=pre_nms_score_threshold,
pad_per_class=False,
clip_boxes=False))
else:
if pre_nms_score_threshold > 0.0:
this_level_boxes, this_level_scores = (
box_ops.filter_boxes_by_scores(
this_level_boxes,
this_level_scores,
pre_nms_score_threshold))
this_level_boxes, this_level_scores = box_ops.top_k_boxes(
this_level_boxes, this_level_scores, k=this_level_pre_nms_top_k)
this_level_roi_scores, this_level_rois = (
nms.sorted_non_max_suppression_padded(
this_level_scores,
this_level_boxes,
max_output_size=this_level_post_nms_top_k,
iou_threshold=nms_iou_threshold))
else:
this_level_rois, this_level_roi_scores = box_ops.top_k_boxes(
this_level_boxes,
this_level_scores,
k=this_level_post_nms_top_k)
rois.append(this_level_rois)
roi_scores.append(this_level_roi_scores)
all_rois = tf.concat(rois, axis=1)
all_roi_scores = tf.concat(roi_scores, axis=1)
with tf.name_scope('top_k_rois'):
_, num_valid_rois = all_roi_scores.get_shape().as_list()
overall_top_k = min(num_valid_rois, num_proposals)
selected_rois, selected_roi_scores = box_ops.top_k_boxes(
all_rois, all_roi_scores, k=overall_top_k)
return selected_rois, selected_roi_scores
@tf_keras.utils.register_keras_serializable(package='Vision')
class MultilevelROIGenerator(tf_keras.layers.Layer):
"""Proposes RoIs for the second stage processing."""
def __init__(self,
pre_nms_top_k: int = 2000,
pre_nms_score_threshold: float = 0.0,
pre_nms_min_size_threshold: float = 0.0,
nms_iou_threshold: float = 0.7,
num_proposals: int = 1000,
test_pre_nms_top_k: int = 1000,
test_pre_nms_score_threshold: float = 0.0,
test_pre_nms_min_size_threshold: float = 0.0,
test_nms_iou_threshold: float = 0.7,
test_num_proposals: int = 1000,
use_batched_nms: bool = False,
**kwargs):
"""Initializes a ROI generator.
The ROI generator transforms the raw predictions from RPN to ROIs.
Args:
pre_nms_top_k: An `int` of the number of top scores proposals to be kept
before applying NMS.
pre_nms_score_threshold: A `float` of the score threshold to apply before
applying NMS. Proposals whose scores are below this threshold are
thrown away.
pre_nms_min_size_threshold: A `float` of the threshold of each side of the
box (w.r.t. the scaled image). Proposals whose sides are below this
threshold are thrown away.
nms_iou_threshold: A `float` in [0, 1], the NMS IoU threshold.
num_proposals: An `int` of the final number of proposals to generate.
test_pre_nms_top_k: An `int` of the number of top scores proposals to be
kept before applying NMS in testing.
test_pre_nms_score_threshold: A `float` of the score threshold to apply
before applying NMS in testing. Proposals whose scores are below this
threshold are thrown away.
test_pre_nms_min_size_threshold: A `float` of the threshold of each side
of the box (w.r.t. the scaled image) in testing. Proposals whose sides
are below this threshold are thrown away.
test_nms_iou_threshold: A `float` in [0, 1] of the NMS IoU threshold in
testing.
test_num_proposals: An `int` of the final number of proposals to generate
in testing.
use_batched_nms: A `bool` of whether or not use
`tf.image.combined_non_max_suppression`.
**kwargs: Additional keyword arguments passed to Layer.
"""
self._config_dict = {
'pre_nms_top_k': pre_nms_top_k,
'pre_nms_score_threshold': pre_nms_score_threshold,
'pre_nms_min_size_threshold': pre_nms_min_size_threshold,
'nms_iou_threshold': nms_iou_threshold,
'num_proposals': num_proposals,
'test_pre_nms_top_k': test_pre_nms_top_k,
'test_pre_nms_score_threshold': test_pre_nms_score_threshold,
'test_pre_nms_min_size_threshold': test_pre_nms_min_size_threshold,
'test_nms_iou_threshold': test_nms_iou_threshold,
'test_num_proposals': test_num_proposals,
'use_batched_nms': use_batched_nms,
}
super(MultilevelROIGenerator, self).__init__(**kwargs)
def call(self,
raw_boxes: Mapping[str, tf.Tensor],
raw_scores: Mapping[str, tf.Tensor],
anchor_boxes: Mapping[str, tf.Tensor],
image_shape: tf.Tensor,
training: Optional[bool] = None):
"""Proposes RoIs given a group of candidates from different FPN levels.
The following describes the steps:
1. For each individual level:
a. Apply sigmoid transform if specified.
b. Decode boxes if specified.
c. Clip boxes if specified.
d. Filter small boxes and those fall outside image if specified.
e. Apply pre-NMS filtering including pre-NMS top k and score
thresholding.
f. Apply NMS.
2. Aggregate post-NMS boxes from each level.
3. Apply an overall top k to generate the final selected RoIs.
Args:
raw_boxes: A `dict` with keys representing FPN levels and values
representing box tenors of shape
[batch, feature_h, feature_w, num_anchors * 4].
raw_scores: A `dict` with keys representing FPN levels and values
representing logit tensors of shape
[batch, feature_h, feature_w, num_anchors].
anchor_boxes: A `dict` with keys representing FPN levels and values
representing anchor box tensors of shape
[batch, feature_h * feature_w * num_anchors, 4].
image_shape: A `tf.Tensor` of shape [batch, 2] where the last dimension
are [height, width] of the scaled image.
training: A `bool` that indicates whether it is in training mode.
Returns:
roi_boxes: A `tf.Tensor` of shape [batch, num_proposals, 4], the proposed
ROIs in the scaled image coordinate.
roi_scores: A `tf.Tensor` of shape [batch, num_proposals], scores of the
proposed ROIs.
"""
roi_boxes, roi_scores = _multilevel_propose_rois(
raw_boxes,
raw_scores,
anchor_boxes,
image_shape,
pre_nms_top_k=(
self._config_dict['pre_nms_top_k'] if training
else self._config_dict['test_pre_nms_top_k']),
pre_nms_score_threshold=(
self._config_dict['pre_nms_score_threshold'] if training
else self._config_dict['test_pre_nms_score_threshold']),
pre_nms_min_size_threshold=(
self._config_dict['pre_nms_min_size_threshold'] if training
else self._config_dict['test_pre_nms_min_size_threshold']),
nms_iou_threshold=(
self._config_dict['nms_iou_threshold'] if training
else self._config_dict['test_nms_iou_threshold']),
num_proposals=(
self._config_dict['num_proposals'] if training
else self._config_dict['test_num_proposals']),
use_batched_nms=self._config_dict['use_batched_nms'],
decode_boxes=True,
clip_boxes=True,
apply_sigmoid_to_score=True)
return roi_boxes, roi_scores
def get_config(self):
return self._config_dict
@classmethod
def from_config(cls, config, custom_objects=None):
return cls(**config)
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