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# 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.
# ==============================================================================
"""Box Head.
Contains Box prediction head classes for different meta architectures.
All the box prediction heads have a predict function that receives the
`features` as the first argument and returns `box_encodings`.
"""
import functools
import tensorflow as tf
from object_detection.predictors.heads import head
slim = tf.contrib.slim
class MaskRCNNBoxHead(head.Head):
"""Box prediction head.
Please refer to Mask RCNN paper:
https://arxiv.org/abs/1703.06870
"""
def __init__(self,
is_training,
num_classes,
fc_hyperparams_fn,
use_dropout,
dropout_keep_prob,
box_code_size,
share_box_across_classes=False):
"""Constructor.
Args:
is_training: Indicates whether the BoxPredictor is in training mode.
num_classes: number of classes. Note that num_classes *does not*
include the background category, so if groundtruth labels take values
in {0, 1, .., K-1}, num_classes=K (and not K+1, even though the
assigned classification targets can range from {0,... K}).
fc_hyperparams_fn: A function to generate tf-slim arg_scope with
hyperparameters for fully connected ops.
use_dropout: Option to use dropout or not. Note that a single dropout
op is applied here prior to both box and class predictions, which stands
in contrast to the ConvolutionalBoxPredictor below.
dropout_keep_prob: Keep probability for dropout.
This is only used if use_dropout is True.
box_code_size: Size of encoding for each box.
share_box_across_classes: Whether to share boxes across classes rather
than use a different box for each class.
"""
super(MaskRCNNBoxHead, self).__init__()
self._is_training = is_training
self._num_classes = num_classes
self._fc_hyperparams_fn = fc_hyperparams_fn
self._use_dropout = use_dropout
self._dropout_keep_prob = dropout_keep_prob
self._box_code_size = box_code_size
self._share_box_across_classes = share_box_across_classes
def predict(self, features, num_predictions_per_location=1):
"""Predicts boxes.
Args:
features: A float tensor of shape [batch_size, height, width,
channels] containing features for a batch of images.
num_predictions_per_location: Int containing number of predictions per
location.
Returns:
box_encodings: A float tensor of shape
[batch_size, 1, num_classes, code_size] representing the location of the
objects.
Raises:
ValueError: If num_predictions_per_location is not 1.
"""
if num_predictions_per_location != 1:
raise ValueError('Only num_predictions_per_location=1 is supported')
spatial_averaged_roi_pooled_features = tf.reduce_mean(
features, [1, 2], keep_dims=True, name='AvgPool')
flattened_roi_pooled_features = slim.flatten(
spatial_averaged_roi_pooled_features)
if self._use_dropout:
flattened_roi_pooled_features = slim.dropout(
flattened_roi_pooled_features,
keep_prob=self._dropout_keep_prob,
is_training=self._is_training)
number_of_boxes = 1
if not self._share_box_across_classes:
number_of_boxes = self._num_classes
with slim.arg_scope(self._fc_hyperparams_fn()):
box_encodings = slim.fully_connected(
flattened_roi_pooled_features,
number_of_boxes * self._box_code_size,
activation_fn=None,
scope='BoxEncodingPredictor')
box_encodings = tf.reshape(box_encodings,
[-1, 1, number_of_boxes, self._box_code_size])
return box_encodings
class ConvolutionalBoxHead(head.Head):
"""Convolutional box prediction head."""
def __init__(self,
is_training,
box_code_size,
kernel_size,
use_depthwise=False):
"""Constructor.
Args:
is_training: Indicates whether the BoxPredictor is in training mode.
box_code_size: Size of encoding for each box.
kernel_size: Size of final convolution kernel. If the
spatial resolution of the feature map is smaller than the kernel size,
then the kernel size is automatically set to be
min(feature_width, feature_height).
use_depthwise: Whether to use depthwise convolutions for prediction
steps. Default is False.
Raises:
ValueError: if min_depth > max_depth.
"""
super(ConvolutionalBoxHead, self).__init__()
self._is_training = is_training
self._box_code_size = box_code_size
self._kernel_size = kernel_size
self._use_depthwise = use_depthwise
def predict(self, features, num_predictions_per_location):
"""Predicts boxes.
Args:
features: A float tensor of shape [batch_size, height, width, channels]
containing image features.
num_predictions_per_location: Number of box predictions to be made per
spatial location. Int specifying number of boxes per location.
Returns:
box_encodings: A float tensors of shape
[batch_size, num_anchors, q, code_size] representing the location of
the objects, where q is 1 or the number of classes.
"""
net = features
if self._use_depthwise:
box_encodings = slim.separable_conv2d(
net, None, [self._kernel_size, self._kernel_size],
padding='SAME', depth_multiplier=1, stride=1,
rate=1, scope='BoxEncodingPredictor_depthwise')
box_encodings = slim.conv2d(
box_encodings,
num_predictions_per_location * self._box_code_size, [1, 1],
activation_fn=None,
normalizer_fn=None,
normalizer_params=None,
scope='BoxEncodingPredictor')
else:
box_encodings = slim.conv2d(
net, num_predictions_per_location * self._box_code_size,
[self._kernel_size, self._kernel_size],
activation_fn=None,
normalizer_fn=None,
normalizer_params=None,
scope='BoxEncodingPredictor')
batch_size = features.get_shape().as_list()[0]
if batch_size is None:
batch_size = tf.shape(features)[0]
box_encodings = tf.reshape(box_encodings,
[batch_size, -1, 1, self._box_code_size])
return box_encodings
# TODO(alirezafathi): See if possible to unify Weight Shared with regular
# convolutional box head.
class WeightSharedConvolutionalBoxHead(head.Head):
"""Weight shared convolutional box prediction head.
This head allows sharing the same set of parameters (weights) when called more
then once on different feature maps.
"""
def __init__(self,
box_code_size,
kernel_size=3,
use_depthwise=False,
box_encodings_clip_range=None):
"""Constructor.
Args:
box_code_size: Size of encoding for each box.
kernel_size: Size of final convolution kernel.
use_depthwise: Whether to use depthwise convolutions for prediction steps.
Default is False.
box_encodings_clip_range: Min and max values for clipping box_encodings.
"""
super(WeightSharedConvolutionalBoxHead, self).__init__()
self._box_code_size = box_code_size
self._kernel_size = kernel_size
self._use_depthwise = use_depthwise
self._box_encodings_clip_range = box_encodings_clip_range
def predict(self, features, num_predictions_per_location):
"""Predicts boxes.
Args:
features: A float tensor of shape [batch_size, height, width, channels]
containing image features.
num_predictions_per_location: Number of box predictions to be made per
spatial location.
Returns:
box_encodings: A float tensor of shape
[batch_size, num_anchors, code_size] representing the location of
the objects.
"""
box_encodings_net = features
if self._use_depthwise:
conv_op = functools.partial(slim.separable_conv2d, depth_multiplier=1)
else:
conv_op = slim.conv2d
box_encodings = conv_op(
box_encodings_net,
num_predictions_per_location * self._box_code_size,
[self._kernel_size, self._kernel_size],
activation_fn=None, stride=1, padding='SAME',
normalizer_fn=None,
scope='BoxPredictor')
batch_size = features.get_shape().as_list()[0]
if batch_size is None:
batch_size = tf.shape(features)[0]
# Clipping the box encodings to make the inference graph TPU friendly.
if self._box_encodings_clip_range is not None:
box_encodings = tf.clip_by_value(
box_encodings, self._box_encodings_clip_range.min,
self._box_encodings_clip_range.max)
box_encodings = tf.reshape(box_encodings,
[batch_size, -1, self._box_code_size])
return box_encodings
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