research/object_detection/predictors/heads/class_head.py
# 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.
# ==============================================================================
"""Class Head.
Contains Class prediction head classes for different meta architectures.
All the class prediction heads have a predict function that receives the
`features` as the first argument and returns class predictions with background.
"""
import functools
import tensorflow.compat.v1 as tf
import tf_slim as slim
from object_detection.predictors.heads import head
from object_detection.utils import shape_utils
class MaskRCNNClassHead(head.Head):
"""Mask RCNN class prediction head.
Please refer to Mask RCNN paper:
https://arxiv.org/abs/1703.06870
"""
def __init__(self,
is_training,
num_class_slots,
fc_hyperparams_fn,
use_dropout,
dropout_keep_prob,
scope='ClassPredictor'):
"""Constructor.
Args:
is_training: Indicates whether the BoxPredictor is in training mode.
num_class_slots: number of class slots. Note that num_class_slots may or
may not include an implicit background category.
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.
scope: Scope name for the convolution operation.
"""
super(MaskRCNNClassHead, self).__init__()
self._is_training = is_training
self._num_class_slots = num_class_slots
self._fc_hyperparams_fn = fc_hyperparams_fn
self._use_dropout = use_dropout
self._dropout_keep_prob = dropout_keep_prob
self._scope = scope
def predict(self, features, num_predictions_per_location=1):
"""Predicts boxes and class scores.
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:
class_predictions_with_background: A float tensor of shape
[batch_size, 1, num_class_slots] representing the class predictions for
the proposals.
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)
with slim.arg_scope(self._fc_hyperparams_fn()):
class_predictions_with_background = slim.fully_connected(
flattened_roi_pooled_features,
self._num_class_slots,
reuse=tf.AUTO_REUSE,
activation_fn=None,
scope=self._scope)
class_predictions_with_background = tf.reshape(
class_predictions_with_background,
[-1, 1, self._num_class_slots])
return class_predictions_with_background
class ConvolutionalClassHead(head.Head):
"""Convolutional class prediction head."""
def __init__(self,
is_training,
num_class_slots,
use_dropout,
dropout_keep_prob,
kernel_size,
apply_sigmoid_to_scores=False,
class_prediction_bias_init=0.0,
use_depthwise=False,
scope='ClassPredictor'):
"""Constructor.
Args:
is_training: Indicates whether the BoxPredictor is in training mode.
num_class_slots: number of class slots. Note that num_class_slots may or
may not include an implicit background category.
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.
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).
apply_sigmoid_to_scores: if True, apply the sigmoid on the output
class_predictions.
class_prediction_bias_init: constant value to initialize bias of the last
conv2d layer before class prediction.
use_depthwise: Whether to use depthwise convolutions for prediction
steps. Default is False.
scope: Scope name for the convolution operation.
Raises:
ValueError: if min_depth > max_depth.
ValueError: if use_depthwise is True and kernel_size is 1.
"""
if use_depthwise and (kernel_size == 1):
raise ValueError('Should not use 1x1 kernel when using depthwise conv')
super(ConvolutionalClassHead, self).__init__()
self._is_training = is_training
self._num_class_slots = num_class_slots
self._use_dropout = use_dropout
self._dropout_keep_prob = dropout_keep_prob
self._kernel_size = kernel_size
self._apply_sigmoid_to_scores = apply_sigmoid_to_scores
self._class_prediction_bias_init = class_prediction_bias_init
self._use_depthwise = use_depthwise
self._scope = scope
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:
class_predictions_with_background: A float tensors of shape
[batch_size, num_anchors, num_class_slots] representing the class
predictions for the proposals.
"""
net = features
if self._use_dropout:
net = slim.dropout(net, keep_prob=self._dropout_keep_prob)
if self._use_depthwise:
depthwise_scope = self._scope + '_depthwise'
class_predictions_with_background = slim.separable_conv2d(
net, None, [self._kernel_size, self._kernel_size],
padding='SAME', depth_multiplier=1, stride=1,
rate=1, scope=depthwise_scope)
class_predictions_with_background = slim.conv2d(
class_predictions_with_background,
num_predictions_per_location * self._num_class_slots, [1, 1],
activation_fn=None,
normalizer_fn=None,
normalizer_params=None,
scope=self._scope)
else:
class_predictions_with_background = slim.conv2d(
net,
num_predictions_per_location * self._num_class_slots,
[self._kernel_size, self._kernel_size],
activation_fn=None,
normalizer_fn=None,
normalizer_params=None,
scope=self._scope,
biases_initializer=tf.constant_initializer(
self._class_prediction_bias_init))
if self._apply_sigmoid_to_scores:
class_predictions_with_background = tf.sigmoid(
class_predictions_with_background)
batch_size = features.get_shape().as_list()[0]
if batch_size is None:
batch_size = tf.shape(features)[0]
class_predictions_with_background = tf.reshape(
class_predictions_with_background,
[batch_size, -1, self._num_class_slots])
return class_predictions_with_background
# TODO(alirezafathi): See if possible to unify Weight Shared with regular
# convolutional class head.
class WeightSharedConvolutionalClassHead(head.Head):
"""Weight shared convolutional class prediction head.
This head allows sharing the same set of parameters (weights) when called more
then once on different feature maps.
"""
def __init__(self,
num_class_slots,
kernel_size=3,
class_prediction_bias_init=0.0,
use_dropout=False,
dropout_keep_prob=0.8,
use_depthwise=False,
score_converter_fn=tf.identity,
return_flat_predictions=True,
scope='ClassPredictor'):
"""Constructor.
Args:
num_class_slots: number of class slots. Note that num_class_slots may or
may not include an implicit background category.
kernel_size: Size of final convolution kernel.
class_prediction_bias_init: constant value to initialize bias of the last
conv2d layer before class prediction.
use_dropout: Whether to apply dropout to class prediction head.
dropout_keep_prob: Probability of keeping activiations.
use_depthwise: Whether to use depthwise convolutions for prediction
steps. Default is False.
score_converter_fn: Callable elementwise nonlinearity (that takes tensors
as inputs and returns tensors).
return_flat_predictions: If true, returns flattened prediction tensor
of shape [batch, height * width * num_predictions_per_location,
box_coder]. Otherwise returns the prediction tensor before reshaping,
whose shape is [batch, height, width, num_predictions_per_location *
num_class_slots].
scope: Scope name for the convolution operation.
Raises:
ValueError: if use_depthwise is True and kernel_size is 1.
"""
if use_depthwise and (kernel_size == 1):
raise ValueError('Should not use 1x1 kernel when using depthwise conv')
super(WeightSharedConvolutionalClassHead, self).__init__()
self._num_class_slots = num_class_slots
self._kernel_size = kernel_size
self._class_prediction_bias_init = class_prediction_bias_init
self._use_dropout = use_dropout
self._dropout_keep_prob = dropout_keep_prob
self._use_depthwise = use_depthwise
self._score_converter_fn = score_converter_fn
self._return_flat_predictions = return_flat_predictions
self._scope = scope
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:
class_predictions_with_background: A tensor of shape
[batch_size, num_anchors, num_class_slots] representing the class
predictions for the proposals, or a tensor of shape [batch, height,
width, num_predictions_per_location * num_class_slots] representing
class predictions before reshaping if self._return_flat_predictions is
False.
"""
class_predictions_net = features
if self._use_dropout:
class_predictions_net = slim.dropout(
class_predictions_net, keep_prob=self._dropout_keep_prob)
if self._use_depthwise:
conv_op = functools.partial(slim.separable_conv2d, depth_multiplier=1)
else:
conv_op = slim.conv2d
class_predictions_with_background = conv_op(
class_predictions_net,
num_predictions_per_location * self._num_class_slots,
[self._kernel_size, self._kernel_size],
activation_fn=None, stride=1, padding='SAME',
normalizer_fn=None,
biases_initializer=tf.constant_initializer(
self._class_prediction_bias_init),
scope=self._scope)
batch_size, height, width = shape_utils.combined_static_and_dynamic_shape(
features)[0:3]
class_predictions_with_background = tf.reshape(
class_predictions_with_background, [
batch_size, height, width, num_predictions_per_location,
self._num_class_slots
])
class_predictions_with_background = self._score_converter_fn(
class_predictions_with_background)
if self._return_flat_predictions:
class_predictions_with_background = tf.reshape(
class_predictions_with_background,
[batch_size, -1, self._num_class_slots])
else:
class_predictions_with_background = tf.reshape(
class_predictions_with_background, [
batch_size, height, width,
num_predictions_per_location * self._num_class_slots
])
return class_predictions_with_background