Add Faster RCNN Resnet V1 FPN Keras feature extractor (tensorflow#8716)

* Initial commit for faster rcnn resnet v1 fpn feature extractor.

1. Setup code structure for fpn feature extractor

* draft for faster rcnn resnet vi fpn feature extractor

* draft for faster rcnn resnet v1 fpn feature extractor

* add seperated class for resnet 50 101 152

* draft for get_box_classifier_feature_extractor_model

* remove unused code

* Init test file for faster_rcnn_fpn_keras_feature extractor

* add unit test for get_proposal_feature_extractor_model

* add unit test for get_proposal_feature_extractor_model smaller input size

* add unit test for get_proposal_feature_extractor_model incorrect dimension

* change keras model output format

* Update size on extract_proposal_features tests

* change default fpn_min_level to 2

* fix error in get_box_classifier_feature_extractor_model

* add shape test for get_box_classifier_feature_extractor_model

* fix coding style

* Fix coding style for feature extractor.

* add faster rcnn resnet v1 fpn feature extractor to model builder

* rename fpn feature extractors

* modify doc string for Feature extractor:

drop word "implementation"

* add todo in get_box_classifier_feature_extractor_model

* remove enable_v2_behavior

* drop unittest test_extract_proposal_features_dies_with_incorrect_rank_inputs

* modify feature extractor name

* remove min_depth and depth_multiplier feature

* Add coarse layers for faster rcnn fpn keras model

1. Add coarse layers
2. Update corresponding unit test to check the size of the coarse layer
is correct

* change the default max_fpn_level to 6

* change unittest since default max_fpn_level is change to 6

research/object_detection/builders/model_builder.py

@@ -52,6 +52,7 @@
   from object_detection.models import faster_rcnn_inception_resnet_v2_keras_feature_extractor as frcnn_inc_res_keras
   from object_detection.models import faster_rcnn_resnet_keras_feature_extractor as frcnn_resnet_keras
   from object_detection.models import ssd_resnet_v1_fpn_keras_feature_extractor as ssd_resnet_v1_fpn_keras
+  from object_detection.models import faster_rcnn_resnet_v1_fpn_keras_feature_extractor as frcnn_resnet_fpn_keras
   from object_detection.models.ssd_mobilenet_v1_fpn_keras_feature_extractor import SSDMobileNetV1FpnKerasFeatureExtractor
   from object_detection.models.ssd_mobilenet_v1_keras_feature_extractor import SSDMobileNetV1KerasFeatureExtractor
   from object_detection.models.ssd_mobilenet_v2_fpn_keras_feature_extractor import SSDMobileNetV2FpnKerasFeatureExtractor
@@ -109,6 +110,12 @@
           frcnn_resnet_keras.FasterRCNNResnet152KerasFeatureExtractor,
       'faster_rcnn_inception_resnet_v2_keras':
       frcnn_inc_res_keras.FasterRCNNInceptionResnetV2KerasFeatureExtractor,
+      'fasret_rcnn_resnet50_fpn_keras':
+          frcnn_resnet_fpn_keras.FasterRCNNResnet50FpnKerasFeatureExtractor,
+      'fasret_rcnn_resnet101_fpn_keras':
+          frcnn_resnet_fpn_keras.FasterRCNNResnet101FpnKerasFeatureExtractor,
+      'fasret_rcnn_resnet152_fpn_keras':
+          frcnn_resnet_fpn_keras.FasterRCNNResnet152FpnKerasFeatureExtractor,
   }
 
   CENTER_NET_EXTRACTOR_FUNCTION_MAP = {

research/object_detection/models/faster_rcnn_resnet_v1_fpn_keras_feature_extractor.py

@@ -0,0 +1,367 @@
+# Copyright 2020 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.
+# ==============================================================================
+
+"""Faster RCNN Keras-based Resnet V1 FPN Feature Extractor."""
+
+import tensorflow.compat.v1 as tf
+
+from object_detection.meta_architectures import faster_rcnn_meta_arch
+from object_detection.models import feature_map_generators
+from object_detection.models.keras_models import resnet_v1
+
+
+_RESNET_MODEL_OUTPUT_LAYERS = {
+    'resnet_v1_50': ['conv2_block3_out', 'conv3_block4_out',
+                     'conv4_block6_out', 'conv5_block3_out'],
+    'resnet_v1_101': ['conv2_block3_out', 'conv3_block4_out',
+                      'conv4_block23_out', 'conv5_block3_out'],
+    'resnet_v1_152': ['conv2_block3_out', 'conv3_block8_out',
+                      'conv4_block36_out', 'conv5_block3_out'],
+}
+
+
+class FasterRCNNResnetV1FpnKerasFeatureExtractor(
+    faster_rcnn_meta_arch.FasterRCNNKerasFeatureExtractor):
+  """Faster RCNN Feature Extractor using Keras-based Resnet V1 FPN features."""
+
+  def __init__(self,
+               is_training,
+               resnet_v1_base_model,
+               resnet_v1_base_model_name,
+               first_stage_features_stride,
+               conv_hyperparams,
+               batch_norm_trainable=False,
+               weight_decay=0.0,
+               fpn_min_level=2,
+               fpn_max_level=6,
+               additional_layer_depth=256,
+               override_base_feature_extractor_hyperparams=False):
+    """Constructor.
+
+    Args:
+      is_training: See base class.
+      resnet_v1_base_model: base resnet v1 network to use. One of
+        the resnet_v1.resnet_v1_{50,101,152} models.
+      resnet_v1_base_model_name: model name under which to construct resnet v1.
+      first_stage_features_stride: See base class.
+      conv_hyperparameters: a `hyperparams_builder.KerasLayerHyperparams` object
+        containing convolution hyperparameters for the layers added on top of
+        the base feature extractor.
+      batch_norm_trainable: See base class.
+      weight_decay: See base class.
+      fpn_min_level: the highest resolution feature map to use in FPN. The valid
+        values are {2, 3, 4, 5} which map to Resnet v1 layers.
+      fpn_max_level: the smallest resolution feature map to construct or use in
+        FPN. FPN constructions uses features maps starting from fpn_min_level
+        upto the fpn_max_level. In the case that there are not enough feature
+        maps in the backbone network, additional feature maps are created by
+        applying stride 2 convolutions until we get the desired number of fpn
+        levels.
+      additional_layer_depth: additional feature map layer channel depth.
+      override_base_feature_extractor_hyperparams: Whether to override
+        hyperparameters of the base feature extractor with the one from
+        `conv_hyperparams`.
+
+    Raises:
+      ValueError: If `first_stage_features_stride` is not 8 or 16.
+    """
+    if first_stage_features_stride != 8 and first_stage_features_stride != 16:
+      raise ValueError('`first_stage_features_stride` must be 8 or 16.')
+
+    super(FasterRCNNResnetV1FpnKerasFeatureExtractor, self).__init__(
+        is_training=is_training,
+        first_stage_features_stride=first_stage_features_stride,
+        batch_norm_trainable=batch_norm_trainable,
+        weight_decay=weight_decay)
+
+    self._resnet_v1_base_model = resnet_v1_base_model
+    self._resnet_v1_base_model_name = resnet_v1_base_model_name
+    self._conv_hyperparams = conv_hyperparams
+    self._fpn_min_level = fpn_min_level
+    self._fpn_max_level = fpn_max_level
+    self._additional_layer_depth = additional_layer_depth
+    self._freeze_batchnorm = (not batch_norm_trainable)
+    self._override_base_feature_extractor_hyperparams = \
+                    override_base_feature_extractor_hyperparams
+    self._resnet_block_names = ['block1', 'block2', 'block3', 'block4']
+    self.classification_backbone = None
+    self._fpn_features_generator = None
+    self._coarse_feature_layers = []
+
+  def preprocess(self, resized_inputs):
+    """Faster R-CNN Resnet V1 preprocessing.
+
+    VGG style channel mean subtraction as described here:
+    https://gist.github.com/ksimonyan/211839e770f7b538e2d8#file-readme-md
+    Note that if the number of channels is not equal to 3, the mean subtraction
+    will be skipped and the original resized_inputs will be returned.
+
+    Args:
+      resized_inputs: A [batch, height_in, width_in, channels] float32 tensor
+        representing a batch of images with values between 0 and 255.0.
+
+    Returns:
+      preprocessed_inputs: A [batch, height_out, width_out, channels] float32
+        tensor representing a batch of images.
+
+    """
+    if resized_inputs.shape.as_list()[3] == 3:
+      channel_means = [123.68, 116.779, 103.939]
+      return resized_inputs - [[channel_means]]
+    else:
+      return resized_inputs
+
+  def get_proposal_feature_extractor_model(self, name=None):
+    """Returns a model that extracts first stage RPN features.
+
+    Extracts features using the Resnet v1 FPN network.
+
+    Args:
+      name: A scope name to construct all variables within.
+
+    Returns:
+      A Keras model that takes preprocessed_inputs:
+        A [batch, height, width, channels] float32 tensor
+        representing a batch of images.
+
+      And returns rpn_feature_map:
+        A list of tensors with shape [batch, height, width, depth]
+    """
+    with tf.name_scope(name):
+      with tf.name_scope('ResnetV1FPN'):
+        full_resnet_v1_model = self._resnet_v1_base_model(
+            batchnorm_training=self._train_batch_norm,
+            conv_hyperparams=(self._conv_hyperparams
+                              if self._override_base_feature_extractor_hyperparams
+                              else None),
+            classes=None,
+            weights=None,
+            include_top=False)
+        output_layers = _RESNET_MODEL_OUTPUT_LAYERS[self._resnet_v1_base_model_name]
+        outputs = [full_resnet_v1_model.get_layer(output_layer_name).output
+                   for output_layer_name in output_layers]
+        self.classification_backbone = tf.keras.Model(
+            inputs=full_resnet_v1_model.inputs,
+            outputs=outputs)
+        backbone_outputs = self.classification_backbone(full_resnet_v1_model.inputs)
+
+        # construct FPN feature generator
+        self._base_fpn_max_level = min(self._fpn_max_level, 5)
+        self._num_levels = self._base_fpn_max_level + 1 - self._fpn_min_level
+        self._fpn_features_generator = (
+            feature_map_generators.KerasFpnTopDownFeatureMaps(
+                num_levels=self._num_levels,
+                depth=self._additional_layer_depth,
+                is_training=self._is_training,
+                conv_hyperparams=self._conv_hyperparams,
+                freeze_batchnorm=self._freeze_batchnorm,
+                name='FeatureMaps'))
+
+        feature_block_list = []
+        for level in range(self._fpn_min_level, self._base_fpn_max_level + 1):
+          feature_block_list.append('block{}'.format(level - 1))
+        feature_block_map = dict(
+            list(zip(self._resnet_block_names, backbone_outputs)))
+        fpn_input_image_features = [
+            (feature_block, feature_block_map[feature_block])
+            for feature_block in feature_block_list]
+        fpn_features = self._fpn_features_generator(fpn_input_image_features)
+
+        # Construct coarse feature layers
+        for i in range(self._base_fpn_max_level, self._fpn_max_level):
+          layers = []
+          layer_name = 'bottom_up_block{}'.format(i)
+          layers.append(
+              tf.keras.layers.Conv2D(
+                  self._additional_layer_depth,
+                  [3, 3],
+                  padding='SAME',
+                  strides=2,
+                  name=layer_name + '_conv',
+                  **self._conv_hyperparams.params()))
+          layers.append(
+              self._conv_hyperparams.build_batch_norm(
+                  training=(self._is_training and not self._freeze_batchnorm),
+                  name=layer_name + '_batchnorm'))
+          layers.append(
+              self._conv_hyperparams.build_activation_layer(
+                  name=layer_name))
+          self._coarse_feature_layers.append(layers)
+
+        feature_maps = []
+        for level in range(self._fpn_min_level, self._base_fpn_max_level + 1):
+          feature_maps.append(fpn_features['top_down_block{}'.format(level-1)])
+        last_feature_map = fpn_features['top_down_block{}'.format(
+            self._base_fpn_max_level - 1)]
+
+        for coarse_feature_layers in self._coarse_feature_layers:
+          for layer in coarse_feature_layers:
+            last_feature_map = layer(last_feature_map)
+          feature_maps.append(last_feature_map)
+
+        feature_extractor_model = tf.keras.models.Model(
+            inputs=full_resnet_v1_model.inputs, outputs=feature_maps)
+        return feature_extractor_model
+
+  def get_box_classifier_feature_extractor_model(self, name=None):
+    """Returns a model that extracts second stage box classifier features.
+
+    Construct two fully connected layer to extract the box classifier features.
+
+    Args:
+      name: A scope name to construct all variables within.
+
+    Returns:
+      A Keras model that takes proposal_feature_maps:
+        A 4-D float tensor with shape
+        [batch_size * self.max_num_proposals, crop_height, crop_width, depth]
+        representing the feature map cropped to each proposal.
+
+      And returns proposal_classifier_features:
+        A 4-D float tensor with shape
+        [batch_size * self.max_num_proposals, 1024]
+        representing box classifier features for each proposal.
+    """
+    with tf.name_scope(name):
+      with tf.name_scope('ResnetV1FPN'):
+        # TODO: Add a batchnorm layer between two fc layers.
+        feature_extractor_model = tf.keras.models.Sequential([
+            tf.keras.layers.Flatten(),
+            tf.keras.layers.Dense(units=1024, activation='relu'),
+            tf.keras.layers.Dense(units=1024, activation='relu')
+        ])
+        return feature_extractor_model
+
+
+class FasterRCNNResnet50FpnKerasFeatureExtractor(
+    FasterRCNNResnetV1FpnKerasFeatureExtractor):
+  """Faster RCNN with Resnet50 FPN feature extractor."""
+
+  def __init__(self,
+               is_training,
+               first_stage_features_stride=16,
+               conv_hyperparams=None,
+               batch_norm_trainable=False,
+               weight_decay=0.0,
+               fpn_min_level=2,
+               fpn_max_level=6,
+               additional_layer_depth=256,
+               override_base_feature_extractor_hyperparams=False):
+    """Constructor.
+
+    Args:
+      is_training: See base class.
+      first_stage_features_stride: See base class.
+      conv_hyperparams: See base class.
+      batch_norm_trainable: See base class.
+      weight_decay: See base class.
+      fpn_min_level: See base class.
+      fpn_max_level: See base class.
+      additional_layer_depth: See base class.
+      override_base_feature_extractor_hyperparams: See base class.
+    """
+    super(FasterRCNNResnet50FpnKerasFeatureExtractor, self).__init__(
+        is_training=is_training,
+        first_stage_features_stride=first_stage_features_stride,
+        conv_hyperparams=conv_hyperparams,
+        resnet_v1_base_model=resnet_v1.resnet_v1_50,
+        resnet_v1_base_model_name='resnet_v1_50',
+        batch_norm_trainable=batch_norm_trainable,
+        weight_decay=weight_decay,
+        fpn_min_level=fpn_min_level,
+        fpn_max_level=fpn_max_level,
+        additional_layer_depth=additional_layer_depth,
+        override_base_feature_extractor_hyperparams=override_base_feature_extractor_hyperparams)
+
+
+class FasterRCNNResnet101FpnKerasFeatureExtractor(
+    FasterRCNNResnetV1FpnKerasFeatureExtractor):
+  """Faster RCNN with Resnet101 FPN feature extractor."""
+  def __init__(self,
+               is_training,
+               first_stage_features_stride=16,
+               conv_hyperparams=None,
+               batch_norm_trainable=False,
+               weight_decay=0.0,
+               fpn_min_level=2,
+               fpn_max_level=6,
+               additional_layer_depth=256,
+               override_base_feature_extractor_hyperparams=False):
+    """Constructor.
+
+    Args:
+      is_training: See base class.
+      first_stage_features_stride: See base class.
+      conv_hyperparams: See base class.
+      batch_norm_trainable: See base class.
+      weight_decay: See base class.
+      fpn_min_level: See base class.
+      fpn_max_level: See base class.
+      additional_layer_depth: See base class.
+      override_base_feature_extractor_hyperparams: See base class.
+    """
+    super(FasterRCNNResnet101FpnKerasFeatureExtractor, self).__init__(
+        is_training=is_training,
+        first_stage_features_stride=first_stage_features_stride,
+        conv_hyperparams=conv_hyperparams,
+        resnet_v1_base_model=resnet_v1.resnet_v1_101,
+        resnet_v1_base_model_name='resnet_v1_101',
+        batch_norm_trainable=batch_norm_trainable,
+        weight_decay=weight_decay,
+        fpn_min_level=fpn_min_level,
+        fpn_max_level=fpn_max_level,
+        additional_layer_depth=additional_layer_depth,
+        override_base_feature_extractor_hyperparams=override_base_feature_extractor_hyperparams)
+
+
+class FasterRCNNResnet152FpnKerasFeatureExtractor(
+    FasterRCNNResnetV1FpnKerasFeatureExtractor):
+  """Faster RCNN with Resnet152 FPN feature extractor."""
+
+  def __init__(self,
+               is_training,
+               first_stage_features_stride=16,
+               conv_hyperparams=None,
+               batch_norm_trainable=False,
+               weight_decay=0.0,
+               fpn_min_level=2,
+               fpn_max_level=6,
+               additional_layer_depth=256,
+               override_base_feature_extractor_hyperparams=False):
+    """Constructor.
+
+    Args:
+      is_training: See base class.
+      first_stage_features_stride: See base class.
+      conv_hyperparams: See base class.
+      batch_norm_trainable: See base class.
+      weight_decay: See base class.
+      fpn_min_level: See base class.
+      fpn_max_level: See base class.
+      additional_layer_depth: See base class.
+      override_base_feature_extractor_hyperparams: See base class.
+    """
+    super(FasterRCNNResnet152FpnKerasFeatureExtractor, self).__init__(
+        is_training=is_training,
+        first_stage_features_stride=first_stage_features_stride,
+        conv_hyperparams=conv_hyperparams,
+        resnet_v1_base_model=resnet_v1.resnet_v1_152,
+        resnet_v1_base_model_name='resnet_v1_152',
+        batch_norm_trainable=batch_norm_trainable,
+        weight_decay=weight_decay,
+        fpn_min_level=fpn_min_level,
+        fpn_max_level=fpn_max_level,
+        additional_layer_depth=additional_layer_depth,
+        override_base_feature_extractor_hyperparams=override_base_feature_extractor_hyperparams)