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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.
"""Base box coder.
Box coders convert between coordinate frames, namely image-centric
(with (0,0) on the top left of image) and anchor-centric (with (0,0) being
defined by a specific anchor).
Users of a BoxCoder can call two methods:
encode: which encodes a box with respect to a given anchor
(or rather, a tensor of boxes wrt a corresponding tensor of anchors) and
decode: which inverts this encoding with a decode operation.
In both cases, the arguments are assumed to be in 1-1 correspondence already;
it is not the job of a BoxCoder to perform matching.
"""
from abc import ABCMeta
from abc import abstractmethod
from abc import abstractproperty
import tensorflow as tf, tf_keras
# Box coder types.
FASTER_RCNN = 'faster_rcnn'
KEYPOINT = 'keypoint'
MEAN_STDDEV = 'mean_stddev'
SQUARE = 'square'
class BoxCoder(object):
"""Abstract base class for box coder."""
__metaclass__ = ABCMeta
@abstractproperty
def code_size(self):
"""Return the size of each code.
This number is a constant and should agree with the output of the `encode`
op (e.g. if rel_codes is the output of self.encode(...), then it should have
shape [N, code_size()]). This abstractproperty should be overridden by
implementations.
Returns:
an integer constant
"""
pass
def encode(self, boxes, anchors):
"""Encode a box list relative to an anchor collection.
Args:
boxes: BoxList holding N boxes to be encoded
anchors: BoxList of N anchors
Returns:
a tensor representing N relative-encoded boxes
"""
with tf.name_scope('Encode'):
return self._encode(boxes, anchors)
def decode(self, rel_codes, anchors):
"""Decode boxes that are encoded relative to an anchor collection.
Args:
rel_codes: a tensor representing N relative-encoded boxes
anchors: BoxList of anchors
Returns:
boxlist: BoxList holding N boxes encoded in the ordinary way (i.e.,
with corners y_min, x_min, y_max, x_max)
"""
with tf.name_scope('Decode'):
return self._decode(rel_codes, anchors)
@abstractmethod
def _encode(self, boxes, anchors):
"""Method to be overriden by implementations.
Args:
boxes: BoxList holding N boxes to be encoded
anchors: BoxList of N anchors
Returns:
a tensor representing N relative-encoded boxes
"""
pass
@abstractmethod
def _decode(self, rel_codes, anchors):
"""Method to be overriden by implementations.
Args:
rel_codes: a tensor representing N relative-encoded boxes
anchors: BoxList of anchors
Returns:
boxlist: BoxList holding N boxes encoded in the ordinary way (i.e.,
with corners y_min, x_min, y_max, x_max)
"""
pass
def batch_decode(encoded_boxes, box_coder, anchors):
"""Decode a batch of encoded boxes.
This op takes a batch of encoded bounding boxes and transforms
them to a batch of bounding boxes specified by their corners in
the order of [y_min, x_min, y_max, x_max].
Args:
encoded_boxes: a float32 tensor of shape [batch_size, num_anchors,
code_size] representing the location of the objects.
box_coder: a BoxCoder object.
anchors: a BoxList of anchors used to encode `encoded_boxes`.
Returns:
decoded_boxes: a float32 tensor of shape [batch_size, num_anchors,
coder_size] representing the corners of the objects in the order
of [y_min, x_min, y_max, x_max].
Raises:
ValueError: if batch sizes of the inputs are inconsistent, or if
the number of anchors inferred from encoded_boxes and anchors are
inconsistent.
"""
encoded_boxes.get_shape().assert_has_rank(3)
if encoded_boxes.get_shape()[1].value != anchors.num_boxes_static():
raise ValueError(
'The number of anchors inferred from encoded_boxes'
' and anchors are inconsistent: shape[1] of encoded_boxes'
' %s should be equal to the number of anchors: %s.' %
(encoded_boxes.get_shape()[1].value, anchors.num_boxes_static()))
decoded_boxes = tf.stack([
box_coder.decode(boxes, anchors).get()
for boxes in tf.unstack(encoded_boxes)
])
return decoded_boxes
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