Copybara import of the project:

--
b3be14bc by Srihari Humbarwadi <sriharihumbarwadi97@gmail.com>:

Added `PanopticMaskRCNNModel` model (#10045)

* Added `PanopticMaskRCNNModel` model

* test checkpoint loading for segmentation objects

* fixed docstring

* subclassed `MaskRCNNModel`

* always enable mask and segmentation heads

* added __init__.py

* added README.md
--
35c3a79f by Srihari Humbarwadi <sriharihumbarwadi97@gmail.com>:

fixed linting errors (#10053)

COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/models/pull/10052 from tensorflow:panoptic-segmentation 35c3a79f
PiperOrigin-RevId: 379834961

official/vision/beta/modeling/maskrcnn_model.py

@@ -16,7 +16,6 @@
 
 from typing import Any, List, Mapping, Optional, Union
 
-# Import libraries
 import tensorflow as tf
 
 from official.vision.beta.ops import anchor
@@ -147,14 +146,18 @@ class MaskRCNNModel(tf.keras.Model):
     model_outputs = {}
 
     # Feature extraction.
-    features = self.backbone(images)
+    backbone_features = self.backbone(images)
     if self.decoder:
-      features = self.decoder(features)
+      features = self.decoder(backbone_features)
+    else:
+      features = backbone_features
 
     # Region proposal network.
     rpn_scores, rpn_boxes = self.rpn_head(features)
 
     model_outputs.update({
+        'backbone_features': backbone_features,
+        'decoder_features': features,
         'rpn_boxes': rpn_boxes,
         'rpn_scores': rpn_scores
     })

official/vision/beta/projects/panoptic_maskrcnn/README.md

+# Panoptic Segmentation
+
+## Description
+
+Panoptic Segmentation combines the two distinct vision tasks - semantic
+segmentation and instance segmentation. These tasks are unified such that, each
+pixel in the image is assigned the label of the class it belongs to, and also
+the instance identifier of the object it a part of.
+
+## Environment setup
+The code can be run on multiple GPUs or TPUs with different distribution
+strategies. See the TensorFlow distributed training
+[guide](https://www.tensorflow.org/guide/distributed_training) for an overview
+of `tf.distribute`.
+
+The code is compatible with TensorFlow 2.4+. See requirements.txt for all
+prerequisites, and you can also install them using the following command. `pip
+install -r ./official/requirements.txt`
+
+**DISCLAIMER**: Panoptic MaskRCNN is still under active development, stay tuned!

official/vision/beta/projects/panoptic_maskrcnn/__init__.py

+# Copyright 2021 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.
+
+# Copyright 2021 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.

official/vision/beta/projects/panoptic_maskrcnn/modeling/panoptic_maskrcnn_model.py

+# Copyright 2021 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.
+
+"""Panoptic Segmentation model."""
+
+from typing import List, Mapping, Optional, Union
+
+import tensorflow as tf
+
+from official.vision.beta.modeling import maskrcnn_model
+
+
+@tf.keras.utils.register_keras_serializable(package='Vision')
+class PanopticMaskRCNNModel(maskrcnn_model.MaskRCNNModel):
+  """The Panoptic Segmentation model."""
+
+  def __init__(self,
+               backbone: tf.keras.Model,
+               decoder: tf.keras.Model,
+               rpn_head: tf.keras.layers.Layer,
+               detection_head: Union[tf.keras.layers.Layer,
+                                     List[tf.keras.layers.Layer]],
+               roi_generator: tf.keras.layers.Layer,
+               roi_sampler: Union[tf.keras.layers.Layer,
+                                  List[tf.keras.layers.Layer]],
+               roi_aligner: tf.keras.layers.Layer,
+               detection_generator: tf.keras.layers.Layer,
+               mask_head: Optional[tf.keras.layers.Layer] = None,
+               mask_sampler: Optional[tf.keras.layers.Layer] = None,
+               mask_roi_aligner: Optional[tf.keras.layers.Layer] = None,
+               segmentation_backbone: Optional[tf.keras.Model] = None,
+               segmentation_decoder: Optional[tf.keras.Model] = None,
+               segmentation_head: tf.keras.layers.Layer = None,
+               class_agnostic_bbox_pred: bool = False,
+               cascade_class_ensemble: bool = False,
+               min_level: Optional[int] = None,
+               max_level: Optional[int] = None,
+               num_scales: Optional[int] = None,
+               aspect_ratios: Optional[List[float]] = None,
+               anchor_size: Optional[float] = None,
+               **kwargs):
+    """Initializes the Panoptic Mask R-CNN model.
+
+    Args:
+      backbone: `tf.keras.Model`, the backbone network.
+      decoder: `tf.keras.Model`, the decoder network.
+      rpn_head: the RPN head.
+      detection_head: the detection head or a list of heads.
+      roi_generator: the ROI generator.
+      roi_sampler: a single ROI sampler or a list of ROI samplers for cascade
+        detection heads.
+      roi_aligner: the ROI aligner.
+      detection_generator: the detection generator.
+      mask_head: the mask head.
+      mask_sampler: the mask sampler.
+      mask_roi_aligner: the ROI alginer for mask prediction.
+      segmentation_backbone: `tf.keras.Model`, the backbone network for the
+        segmentation head for panoptic task. Providing `segmentation_backbone`
+        will allow the segmentation head to use a standlone backbone. Setting
+        `segmentation_backbone=None` would enable backbone sharing between the
+        MaskRCNN model and segmentation head.
+      segmentation_decoder: `tf.keras.Model`, the decoder network for the
+        segmentation head for panoptic task. Providing `segmentation_decoder`
+        will allow the segmentation head to use a standlone decoder. Setting
+        `segmentation_decoder=None` would enable decoder sharing between the
+        MaskRCNN model and segmentation head. Decoders can only be shared when
+        `segmentation_backbone` is shared as well.
+      segmentation_head: segmentatation head for panoptic task.
+      class_agnostic_bbox_pred: if True, perform class agnostic bounding box
+        prediction. Needs to be `True` for Cascade RCNN models.
+      cascade_class_ensemble: if True, ensemble classification scores over all
+        detection heads.
+      min_level: Minimum level in output feature maps.
+      max_level: Maximum level in output feature maps.
+      num_scales: A number representing intermediate scales added on each level.
+        For instances, num_scales=2 adds one additional intermediate anchor
+        scales [2^0, 2^0.5] on each level.
+      aspect_ratios: A list representing the aspect raito anchors added on each
+        level. The number indicates the ratio of width to height. For instances,
+        aspect_ratios=[1.0, 2.0, 0.5] adds three anchors on each scale level.
+      anchor_size: A number representing the scale of size of the base anchor to
+        the feature stride 2^level.
+      **kwargs: keyword arguments to be passed.
+    """
+    super(PanopticMaskRCNNModel, self).__init__(
+        backbone=backbone,
+        decoder=decoder,
+        rpn_head=rpn_head,
+        detection_head=detection_head,
+        roi_generator=roi_generator,
+        roi_sampler=roi_sampler,
+        roi_aligner=roi_aligner,
+        detection_generator=detection_generator,
+        mask_head=mask_head,
+        mask_sampler=mask_sampler,
+        mask_roi_aligner=mask_roi_aligner,
+        class_agnostic_bbox_pred=class_agnostic_bbox_pred,
+        cascade_class_ensemble=cascade_class_ensemble,
+        min_level=min_level,
+        max_level=max_level,
+        num_scales=num_scales,
+        aspect_ratios=aspect_ratios,
+        anchor_size=anchor_size,
+        **kwargs)
+
+    self._config_dict.update({
+        'segmentation_backbone': segmentation_backbone,
+        'segmentation_decoder': segmentation_decoder,
+        'segmentation_head': segmentation_head
+    })
+
+    if not self._include_mask:
+      raise ValueError(
+          '`mask_head` needs to be provided for Panoptic Mask R-CNN.')
+    if segmentation_backbone is not None and segmentation_decoder is None:
+      raise ValueError(
+          '`segmentation_decoder` needs to be provided for Panoptic Mask R-CNN'
+          'if `backbone` is not shared.')
+
+    self.segmentation_backbone = segmentation_backbone
+    self.segmentation_decoder = segmentation_decoder
+    self.segmentation_head = segmentation_head
+
+  def call(self,
+           images: tf.Tensor,
+           image_shape: tf.Tensor,
+           anchor_boxes: Optional[Mapping[str, tf.Tensor]] = None,
+           gt_boxes: Optional[tf.Tensor] = None,
+           gt_classes: Optional[tf.Tensor] = None,
+           gt_masks: Optional[tf.Tensor] = None,
+           training: Optional[bool] = None) -> Mapping[str, tf.Tensor]:
+    model_outputs = super(PanopticMaskRCNNModel, self).call(
+        images=images,
+        image_shape=image_shape,
+        anchor_boxes=anchor_boxes,
+        gt_boxes=gt_boxes,
+        gt_classes=gt_classes,
+        gt_masks=gt_masks,
+        training=training)
+
+    if self.segmentation_backbone is not None:
+      backbone_features = self.segmentation_backbone(images, training=training)
+    else:
+      backbone_features = model_outputs['backbone_features']
+
+    if self.segmentation_decoder is not None:
+      decoder_features = self.segmentation_decoder(
+          backbone_features, training=training)
+    else:
+      decoder_features = model_outputs['decoder_features']
+
+    segmentation_outputs = self.segmentation_head(
+        backbone_features, decoder_features, training=training)
+
+    model_outputs.update({
+        'segmentation_outputs': segmentation_outputs,
+    })
+
+    return model_outputs
+
+  @property
+  def checkpoint_items(
+      self) -> Mapping[str, Union[tf.keras.Model, tf.keras.layers.Layer]]:
+    """Returns a dictionary of items to be additionally checkpointed."""
+    items = super(PanopticMaskRCNNModel, self).checkpoint_items
+    if self.segmentation_backbone is not None:
+      items.update(segmentation_backbone=self.segmentation_backbone)
+    if self.segmentation_decoder is not None:
+      items.update(segmentation_decoder=self.segmentation_decoder)
+    items.update(segmentation_head=self.segmentation_head)
+    return items

official/vision/beta/projects/panoptic_maskrcnn/modeling/panoptic_maskrcnn_model_test.py

+# Copyright 2021 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.
+
+"""Tests for panoptic_maskrcnn_model.py."""
+
+import os
+
+from absl.testing import parameterized
+import numpy as np
+import tensorflow as tf
+
+from tensorflow.python.distribute import combinations
+from tensorflow.python.distribute import strategy_combinations
+from official.vision.beta.modeling.backbones import resnet
+from official.vision.beta.modeling.decoders import aspp
+from official.vision.beta.modeling.decoders import fpn
+from official.vision.beta.modeling.heads import dense_prediction_heads
+from official.vision.beta.modeling.heads import instance_heads
+from official.vision.beta.modeling.heads import segmentation_heads
+from official.vision.beta.modeling.layers import detection_generator
+from official.vision.beta.modeling.layers import mask_sampler
+from official.vision.beta.modeling.layers import roi_aligner
+from official.vision.beta.modeling.layers import roi_generator
+from official.vision.beta.modeling.layers import roi_sampler
+from official.vision.beta.ops import anchor
+from official.vision.beta.projects.panoptic_maskrcnn.modeling import panoptic_maskrcnn_model
+
+
+class PanopticMaskRCNNModelTest(parameterized.TestCase, tf.test.TestCase):
+
+  @combinations.generate(
+      combinations.combine(
+          use_separable_conv=[True, False],
+          build_anchor_boxes=[True, False],
+          shared_backbone=[True, False],
+          shared_decoder=[True, False],
+          is_training=[True, False]))
+  def test_build_model(self,
+                       use_separable_conv,
+                       build_anchor_boxes,
+                       shared_backbone,
+                       shared_decoder,
+                       is_training=True):
+    num_classes = 3
+    min_level = 3
+    max_level = 7
+    num_scales = 3
+    aspect_ratios = [1.0]
+    anchor_size = 3
+    resnet_model_id = 50
+    segmentation_resnet_model_id = 50
+    segmentation_output_stride = 16
+    aspp_dilation_rates = [6, 12, 18]
+    aspp_decoder_level = int(np.math.log2(segmentation_output_stride))
+    fpn_decoder_level = 3
+    num_anchors_per_location = num_scales * len(aspect_ratios)
+    image_size = 128
+    images = np.random.rand(2, image_size, image_size, 3)
+    image_shape = np.array([[image_size, image_size], [image_size, image_size]])
+    shared_decoder = shared_decoder and shared_backbone
+    if build_anchor_boxes:
+      anchor_boxes = anchor.Anchor(
+          min_level=min_level,
+          max_level=max_level,
+          num_scales=num_scales,
+          aspect_ratios=aspect_ratios,
+          anchor_size=3,
+          image_size=(image_size, image_size)).multilevel_boxes
+      for l in anchor_boxes:
+        anchor_boxes[l] = tf.tile(
+            tf.expand_dims(anchor_boxes[l], axis=0), [2, 1, 1, 1])
+    else:
+      anchor_boxes = None
+
+    backbone = resnet.ResNet(model_id=resnet_model_id)
+    decoder = fpn.FPN(
+        input_specs=backbone.output_specs,
+        min_level=min_level,
+        max_level=max_level,
+        use_separable_conv=use_separable_conv)
+    rpn_head = dense_prediction_heads.RPNHead(
+        min_level=min_level,
+        max_level=max_level,
+        num_anchors_per_location=num_anchors_per_location,
+        num_convs=1)
+    detection_head = instance_heads.DetectionHead(num_classes=num_classes)
+    roi_generator_obj = roi_generator.MultilevelROIGenerator()
+    roi_sampler_obj = roi_sampler.ROISampler()
+    roi_aligner_obj = roi_aligner.MultilevelROIAligner()
+    detection_generator_obj = detection_generator.DetectionGenerator()
+    mask_head = instance_heads.MaskHead(
+        num_classes=num_classes, upsample_factor=2)
+    mask_sampler_obj = mask_sampler.MaskSampler(
+        mask_target_size=28, num_sampled_masks=1)
+    mask_roi_aligner_obj = roi_aligner.MultilevelROIAligner(crop_size=14)
+
+    if shared_backbone:
+      segmentation_backbone = None
+    else:
+      segmentation_backbone = resnet.ResNet(
+          model_id=segmentation_resnet_model_id)
+    if not shared_decoder:
+      level = aspp_decoder_level
+      segmentation_decoder = aspp.ASPP(
+          level=level, dilation_rates=aspp_dilation_rates)
+    else:
+      level = fpn_decoder_level
+      segmentation_decoder = None
+    segmentation_head = segmentation_heads.SegmentationHead(
+        num_classes=2,  # stuff and common class for things,
+        level=level,
+        num_convs=2)
+
+    model = panoptic_maskrcnn_model.PanopticMaskRCNNModel(
+        backbone,
+        decoder,
+        rpn_head,
+        detection_head,
+        roi_generator_obj,
+        roi_sampler_obj,
+        roi_aligner_obj,
+        detection_generator_obj,
+        mask_head,
+        mask_sampler_obj,
+        mask_roi_aligner_obj,
+        segmentation_backbone=segmentation_backbone,
+        segmentation_decoder=segmentation_decoder,
+        segmentation_head=segmentation_head,
+        min_level=min_level,
+        max_level=max_level,
+        num_scales=num_scales,
+        aspect_ratios=aspect_ratios,
+        anchor_size=anchor_size)
+
+    gt_boxes = np.array(
+        [[[10, 10, 15, 15], [2.5, 2.5, 7.5, 7.5], [-1, -1, -1, -1]],
+         [[100, 100, 150, 150], [-1, -1, -1, -1], [-1, -1, -1, -1]]],
+        dtype=np.float32)
+    gt_classes = np.array([[2, 1, -1], [1, -1, -1]], dtype=np.int32)
+    gt_masks = np.ones((2, 3, 100, 100))
+
+    # Results will be checked in test_forward.
+    _ = model(
+        images,
+        image_shape,
+        anchor_boxes,
+        gt_boxes,
+        gt_classes,
+        gt_masks,
+        training=is_training)
+
+  @combinations.generate(
+      combinations.combine(
+          strategy=[
+              strategy_combinations.cloud_tpu_strategy,
+              strategy_combinations.one_device_strategy_gpu,
+          ],
+          shared_backbone=[True, False],
+          shared_decoder=[True, False],
+          training=[True, False],
+      ))
+  def test_forward(self, strategy, training,
+                   shared_backbone, shared_decoder):
+    num_classes = 3
+    min_level = 3
+    max_level = 4
+    num_scales = 3
+    aspect_ratios = [1.0]
+    anchor_size = 3
+    segmentation_resnet_model_id = 101
+    segmentation_output_stride = 16
+    aspp_dilation_rates = [6, 12, 18]
+    aspp_decoder_level = int(np.math.log2(segmentation_output_stride))
+    fpn_decoder_level = 3
+
+    class_agnostic_bbox_pred = False
+    cascade_class_ensemble = False
+
+    image_size = (256, 256)
+    images = np.random.rand(2, image_size[0], image_size[1], 3)
+    image_shape = np.array([[224, 100], [100, 224]])
+    shared_decoder = shared_decoder and shared_backbone
+    with strategy.scope():
+
+      anchor_boxes = anchor.Anchor(
+          min_level=min_level,
+          max_level=max_level,
+          num_scales=num_scales,
+          aspect_ratios=aspect_ratios,
+          anchor_size=anchor_size,
+          image_size=image_size).multilevel_boxes
+
+      num_anchors_per_location = len(aspect_ratios) * num_scales
+
+      input_specs = tf.keras.layers.InputSpec(shape=[None, None, None, 3])
+      backbone = resnet.ResNet(model_id=50, input_specs=input_specs)
+      decoder = fpn.FPN(
+          min_level=min_level,
+          max_level=max_level,
+          input_specs=backbone.output_specs)
+      rpn_head = dense_prediction_heads.RPNHead(
+          min_level=min_level,
+          max_level=max_level,
+          num_anchors_per_location=num_anchors_per_location)
+      detection_head = instance_heads.DetectionHead(
+          num_classes=num_classes,
+          class_agnostic_bbox_pred=class_agnostic_bbox_pred)
+      roi_generator_obj = roi_generator.MultilevelROIGenerator()
+
+      roi_sampler_cascade = []
+      roi_sampler_obj = roi_sampler.ROISampler()
+      roi_sampler_cascade.append(roi_sampler_obj)
+      roi_aligner_obj = roi_aligner.MultilevelROIAligner()
+      detection_generator_obj = detection_generator.DetectionGenerator()
+      mask_head = instance_heads.MaskHead(
+          num_classes=num_classes, upsample_factor=2)
+      mask_sampler_obj = mask_sampler.MaskSampler(
+          mask_target_size=28, num_sampled_masks=1)
+      mask_roi_aligner_obj = roi_aligner.MultilevelROIAligner(crop_size=14)
+
+      if shared_backbone:
+        segmentation_backbone = None
+      else:
+        segmentation_backbone = resnet.ResNet(
+            model_id=segmentation_resnet_model_id)
+      if not shared_decoder:
+        level = aspp_decoder_level
+        segmentation_decoder = aspp.ASPP(
+            level=level, dilation_rates=aspp_dilation_rates)
+      else:
+        level = fpn_decoder_level
+        segmentation_decoder = None
+      segmentation_head = segmentation_heads.SegmentationHead(
+          num_classes=2,  # stuff and common class for things,
+          level=level,
+          num_convs=2)
+
+      model = panoptic_maskrcnn_model.PanopticMaskRCNNModel(
+          backbone,
+          decoder,
+          rpn_head,
+          detection_head,
+          roi_generator_obj,
+          roi_sampler_obj,
+          roi_aligner_obj,
+          detection_generator_obj,
+          mask_head,
+          mask_sampler_obj,
+          mask_roi_aligner_obj,
+          segmentation_backbone=segmentation_backbone,
+          segmentation_decoder=segmentation_decoder,
+          segmentation_head=segmentation_head,
+          class_agnostic_bbox_pred=class_agnostic_bbox_pred,
+          cascade_class_ensemble=cascade_class_ensemble,
+          min_level=min_level,
+          max_level=max_level,
+          num_scales=num_scales,
+          aspect_ratios=aspect_ratios,
+          anchor_size=anchor_size)
+
+      gt_boxes = np.array(
+          [[[10, 10, 15, 15], [2.5, 2.5, 7.5, 7.5], [-1, -1, -1, -1]],
+           [[100, 100, 150, 150], [-1, -1, -1, -1], [-1, -1, -1, -1]]],
+          dtype=np.float32)
+      gt_classes = np.array([[2, 1, -1], [1, -1, -1]], dtype=np.int32)
+      gt_masks = np.ones((2, 3, 100, 100))
+
+      results = model(
+          images,
+          image_shape,
+          anchor_boxes,
+          gt_boxes,
+          gt_classes,
+          gt_masks,
+          training=training)
+
+    self.assertIn('rpn_boxes', results)
+    self.assertIn('rpn_scores', results)
+    if training:
+      self.assertIn('class_targets', results)
+      self.assertIn('box_targets', results)
+      self.assertIn('class_outputs', results)
+      self.assertIn('box_outputs', results)
+      self.assertIn('mask_outputs', results)
+    else:
+      self.assertIn('detection_boxes', results)
+      self.assertIn('detection_scores', results)
+      self.assertIn('detection_classes', results)
+      self.assertIn('num_detections', results)
+      self.assertIn('detection_masks', results)
+      self.assertIn('segmentation_outputs', results)
+      self.assertAllEqual(
+          [2, image_size[0] // (2**level), image_size[1] // (2**level), 2],
+          results['segmentation_outputs'].numpy().shape)
+
+  @combinations.generate(
+      combinations.combine(
+          shared_backbone=[True, False], shared_decoder=[True, False]))
+  def test_serialize_deserialize(self, shared_backbone, shared_decoder):
+    input_specs = tf.keras.layers.InputSpec(shape=[None, None, None, 3])
+    backbone = resnet.ResNet(model_id=50, input_specs=input_specs)
+    decoder = fpn.FPN(
+        min_level=3, max_level=7, input_specs=backbone.output_specs)
+    rpn_head = dense_prediction_heads.RPNHead(
+        min_level=3, max_level=7, num_anchors_per_location=3)
+    detection_head = instance_heads.DetectionHead(num_classes=2)
+    roi_generator_obj = roi_generator.MultilevelROIGenerator()
+    roi_sampler_obj = roi_sampler.ROISampler()
+    roi_aligner_obj = roi_aligner.MultilevelROIAligner()
+    detection_generator_obj = detection_generator.DetectionGenerator()
+    segmentation_resnet_model_id = 101
+    segmentation_output_stride = 16
+    aspp_dilation_rates = [6, 12, 18]
+    aspp_decoder_level = int(np.math.log2(segmentation_output_stride))
+    fpn_decoder_level = 3
+    shared_decoder = shared_decoder and shared_backbone
+    mask_head = instance_heads.MaskHead(num_classes=2, upsample_factor=2)
+    mask_sampler_obj = mask_sampler.MaskSampler(
+        mask_target_size=28, num_sampled_masks=1)
+    mask_roi_aligner_obj = roi_aligner.MultilevelROIAligner(crop_size=14)
+
+    if shared_backbone:
+      segmentation_backbone = None
+    else:
+      segmentation_backbone = resnet.ResNet(
+          model_id=segmentation_resnet_model_id)
+    if not shared_decoder:
+      level = aspp_decoder_level
+      segmentation_decoder = aspp.ASPP(
+          level=level, dilation_rates=aspp_dilation_rates)
+    else:
+      level = fpn_decoder_level
+      segmentation_decoder = None
+    segmentation_head = segmentation_heads.SegmentationHead(
+        num_classes=2,  # stuff and common class for things,
+        level=level,
+        num_convs=2)
+
+    model = panoptic_maskrcnn_model.PanopticMaskRCNNModel(
+        backbone,
+        decoder,
+        rpn_head,
+        detection_head,
+        roi_generator_obj,
+        roi_sampler_obj,
+        roi_aligner_obj,
+        detection_generator_obj,
+        mask_head,
+        mask_sampler_obj,
+        mask_roi_aligner_obj,
+        segmentation_backbone=segmentation_backbone,
+        segmentation_decoder=segmentation_decoder,
+        segmentation_head=segmentation_head,
+        min_level=3,
+        max_level=7,
+        num_scales=3,
+        aspect_ratios=[1.0],
+        anchor_size=3)
+
+    config = model.get_config()
+    new_model = panoptic_maskrcnn_model.PanopticMaskRCNNModel.from_config(
+        config)
+
+    # Validate that the config can be forced to JSON.
+    _ = new_model.to_json()
+
+    # If the serialization was successful, the new config should match the old.
+    self.assertAllEqual(model.get_config(), new_model.get_config())
+
+  @combinations.generate(
+      combinations.combine(
+          shared_backbone=[True, False], shared_decoder=[True, False]))
+  def test_checkpoint(self, shared_backbone, shared_decoder):
+    input_specs = tf.keras.layers.InputSpec(shape=[None, None, None, 3])
+    backbone = resnet.ResNet(model_id=50, input_specs=input_specs)
+    decoder = fpn.FPN(
+        min_level=3, max_level=7, input_specs=backbone.output_specs)
+    rpn_head = dense_prediction_heads.RPNHead(
+        min_level=3, max_level=7, num_anchors_per_location=3)
+    detection_head = instance_heads.DetectionHead(num_classes=2)
+    roi_generator_obj = roi_generator.MultilevelROIGenerator()
+    roi_sampler_obj = roi_sampler.ROISampler()
+    roi_aligner_obj = roi_aligner.MultilevelROIAligner()
+    detection_generator_obj = detection_generator.DetectionGenerator()
+    segmentation_resnet_model_id = 101
+    segmentation_output_stride = 16
+    aspp_dilation_rates = [6, 12, 18]
+    aspp_decoder_level = int(np.math.log2(segmentation_output_stride))
+    fpn_decoder_level = 3
+    shared_decoder = shared_decoder and shared_backbone
+    mask_head = instance_heads.MaskHead(num_classes=2, upsample_factor=2)
+    mask_sampler_obj = mask_sampler.MaskSampler(
+        mask_target_size=28, num_sampled_masks=1)
+    mask_roi_aligner_obj = roi_aligner.MultilevelROIAligner(crop_size=14)
+
+    if shared_backbone:
+      segmentation_backbone = None
+    else:
+      segmentation_backbone = resnet.ResNet(
+          model_id=segmentation_resnet_model_id)
+    if not shared_decoder:
+      level = aspp_decoder_level
+      segmentation_decoder = aspp.ASPP(
+          level=level, dilation_rates=aspp_dilation_rates)
+    else:
+      level = fpn_decoder_level
+      segmentation_decoder = None
+    segmentation_head = segmentation_heads.SegmentationHead(
+        num_classes=2,  # stuff and common class for things,
+        level=level,
+        num_convs=2)
+
+    model = panoptic_maskrcnn_model.PanopticMaskRCNNModel(
+        backbone,
+        decoder,
+        rpn_head,
+        detection_head,
+        roi_generator_obj,
+        roi_sampler_obj,
+        roi_aligner_obj,
+        detection_generator_obj,
+        mask_head,
+        mask_sampler_obj,
+        mask_roi_aligner_obj,
+        segmentation_backbone=segmentation_backbone,
+        segmentation_decoder=segmentation_decoder,
+        segmentation_head=segmentation_head,
+        min_level=3,
+        max_level=7,
+        num_scales=3,
+        aspect_ratios=[1.0],
+        anchor_size=3)
+    expect_checkpoint_items = dict(
+        backbone=backbone,
+        decoder=decoder,
+        rpn_head=rpn_head,
+        detection_head=[detection_head])
+    expect_checkpoint_items['mask_head'] = mask_head
+    if not shared_backbone:
+      expect_checkpoint_items['segmentation_backbone'] = segmentation_backbone
+    if not shared_decoder:
+      expect_checkpoint_items['segmentation_decoder'] = segmentation_decoder
+    expect_checkpoint_items['segmentation_head'] = segmentation_head
+    self.assertAllEqual(expect_checkpoint_items, model.checkpoint_items)
+
+    # Test save and load checkpoints.
+    ckpt = tf.train.Checkpoint(model=model, **model.checkpoint_items)
+    save_dir = self.create_tempdir().full_path
+    ckpt.save(os.path.join(save_dir, 'ckpt'))
+
+    partial_ckpt = tf.train.Checkpoint(backbone=backbone)
+    partial_ckpt.restore(tf.train.latest_checkpoint(
+        save_dir)).expect_partial().assert_existing_objects_matched()
+
+    partial_ckpt_mask = tf.train.Checkpoint(
+        backbone=backbone, mask_head=mask_head)
+    partial_ckpt_mask.restore(tf.train.latest_checkpoint(
+        save_dir)).expect_partial().assert_existing_objects_matched()
+
+    if not shared_backbone:
+      partial_ckpt_segmentation = tf.train.Checkpoint(
+          segmentation_backbone=segmentation_backbone,
+          segmentation_decoder=segmentation_decoder,
+          segmentation_head=segmentation_head)
+    elif not shared_decoder:
+      partial_ckpt_segmentation = tf.train.Checkpoint(
+          segmentation_decoder=segmentation_decoder,
+          segmentation_head=segmentation_head)
+    else:
+      partial_ckpt_segmentation = tf.train.Checkpoint(
+          segmentation_head=segmentation_head)
+
+    partial_ckpt_segmentation.restore(tf.train.latest_checkpoint(
+        save_dir)).expect_partial().assert_existing_objects_matched()
+
+
+if __name__ == '__main__':
+  tf.test.main()