# Copyright 2017 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.
# ==============================================================================
"""Builder function for post processing operations."""
import functools
import tensorflow as tf
from object_detection.core import post_processing
from object_detection.protos import post_processing_pb2
def build(post_processing_config):
"""Builds callables for post-processing operations.
Builds callables for non-max suppression and score conversion based on the
configuration.
Non-max suppression callable takes `boxes`, `scores`, and optionally
`clip_window`, `parallel_iterations` `masks, and `scope` as inputs. It returns
`nms_boxes`, `nms_scores`, `nms_classes` `nms_masks` and `num_detections`. See
post_processing.batch_multiclass_non_max_suppression for the type and shape
of these tensors.
Score converter callable should be called with `input` tensor. The callable
returns the output from one of 3 tf operations based on the configuration -
tf.identity, tf.sigmoid or tf.nn.softmax. See tensorflow documentation for
argument and return value descriptions.
Args:
post_processing_config: post_processing.proto object containing the
parameters for the post-processing operations.
Returns:
non_max_suppressor_fn: Callable for non-max suppression.
score_converter_fn: Callable for score conversion.
Raises:
ValueError: if the post_processing_config is of incorrect type.
"""
if not isinstance(post_processing_config, post_processing_pb2.PostProcessing):
raise ValueError('post_processing_config not of type '
'post_processing_pb2.Postprocessing.')
non_max_suppressor_fn = _build_non_max_suppressor(
post_processing_config.batch_non_max_suppression)
score_converter_fn = _build_score_converter(
post_processing_config.score_converter,
post_processing_config.logit_scale)
return non_max_suppressor_fn, score_converter_fn
def _build_non_max_suppressor(nms_config):
"""Builds non-max suppresson based on the nms config.
Args:
nms_config: post_processing_pb2.PostProcessing.BatchNonMaxSuppression proto.
Returns:
non_max_suppressor_fn: Callable non-max suppressor.
Raises:
ValueError: On incorrect iou_threshold or on incompatible values of
max_total_detections and max_detections_per_class.
"""
if nms_config.iou_threshold < 0 or nms_config.iou_threshold > 1.0:
raise ValueError('iou_threshold not in [0, 1.0].')
if nms_config.max_detections_per_class > nms_config.max_total_detections:
raise ValueError('max_detections_per_class should be no greater than '
'max_total_detections.')
non_max_suppressor_fn = functools.partial(
post_processing.batch_multiclass_non_max_suppression,
score_thresh=nms_config.score_threshold,
iou_thresh=nms_config.iou_threshold,
max_size_per_class=nms_config.max_detections_per_class,
max_total_size=nms_config.max_total_detections)
return non_max_suppressor_fn
def _score_converter_fn_with_logit_scale(tf_score_converter_fn, logit_scale):
"""Create a function to scale logits then apply a Tensorflow function."""
def score_converter_fn(logits):
scaled_logits = tf.divide(logits, logit_scale, name='scale_logits')
return tf_score_converter_fn(scaled_logits, name='convert_scores')
score_converter_fn.__name__ = '%s_with_logit_scale' % (
tf_score_converter_fn.__name__)
return score_converter_fn
def _build_score_converter(score_converter_config, logit_scale):
"""Builds score converter based on the config.
Builds one of [tf.identity, tf.sigmoid, tf.softmax] score converters based on
the config.
Args:
score_converter_config: post_processing_pb2.PostProcessing.score_converter.
logit_scale: temperature to use for SOFTMAX score_converter.
Returns:
Callable score converter op.
Raises:
ValueError: On unknown score converter.
"""
if score_converter_config == post_processing_pb2.PostProcessing.IDENTITY:
return _score_converter_fn_with_logit_scale(tf.identity, logit_scale)
if score_converter_config == post_processing_pb2.PostProcessing.SIGMOID:
return _score_converter_fn_with_logit_scale(tf.sigmoid, logit_scale)
if score_converter_config == post_processing_pb2.PostProcessing.SOFTMAX:
return _score_converter_fn_with_logit_scale(tf.nn.softmax, logit_scale)
raise ValueError('Unknown score converter.')
