added tflite support (experimental) (#40)

* tflite support (wip)

* linting

* just check for "resnet" in model path

* fallback to single tensor input

* adjust image_data shape to expected input shape

also optional image_size input

* removed commented out code

* only resize tensor if input image doesn't match

* added command to convert to tflite

* added --model-architecture argument

* added quantization arguments

* updated readme

* linting

* typo in readme

* improved wording in readme

Author: de-code

.pylintrc

@@ -10,4 +10,5 @@ disable=
     too-few-public-methods,
     too-many-arguments,
     too-many-instance-attributes,
+    duplicate-code,
     invalid-name

README.md

@@ -176,6 +176,31 @@ python -m tf_bodypix \
     --threshold=0.75
 ```
 
+## TensorFlow Lite support (experimental)
+
+The model path may also point to a TensorFlow Lite model (`.tflite` extension). Whether that actually improves performance may depend on the platform and available hardware.
+
+You could convert one of the available TensorFlow JS models to TensorFlow Lite using the following command:
+
+```bash
+python -m tf_bodypix \
+    convert-to-tflite \
+    --model-path \
+    "https://storage.googleapis.com/tfjs-models/savedmodel/bodypix/mobilenet/float/075/model-stride16.json" \
+    --optimize \
+    --quantization-type=float16 \
+    --output-model-file "./mobilenet-float16-stride16.tflite"
+```
+
+The above command is provided for convenience.
+You may use alternative methods depending on your preference and requirements.
+
+Relevant links:
+
+* [TensorFlow Lite converter](https://www.tensorflow.org/lite/convert/)
+* [TF Lite post_training_quantization](https://www.tensorflow.org/lite/performance/post_training_quantization)
+* [TF GitHub #40183](https://github.com/tensorflow/tensorflow/issues/40183).
+
 ## Acknowledgements
 
 * [Original TensorFlow JS Implementation of BodyPix](https://github.com/tensorflow/tfjs-models/tree/body-pix-v2.0.4/body-pix)

tests/cli_test.py

@@ -2,6 +2,7 @@
 from pathlib import Path
 
 from tf_bodypix.download import BodyPixModelPaths
+from tf_bodypix.model import ModelArchitectureNames
 from tf_bodypix.cli import main
 
 
@@ -87,3 +88,22 @@ def test_should_list_all_default_model_urls(self, capsys):
         LOGGER.debug('output_urls: %s', output_urls)
         missing_urls = set(expected_urls) - set(output_urls)
         assert not missing_urls
+
+    def test_should_be_able_to_convert_to_tflite_and_use_model(self, temp_dir: Path):
+        output_model_file = temp_dir / 'model.tflite'
+        main([
+            'convert-to-tflite',
+            '--model-path=%s' % BodyPixModelPaths.MOBILENET_FLOAT_75_STRIDE_16,
+            '--optimize',
+            '--quantization-type=int8',
+            '--output-model-file=%s' % output_model_file
+        ])
+        output_image_path = temp_dir / 'mask.jpg'
+        main([
+            'draw-mask',
+            '--model-path=%s' % output_model_file,
+            '--model-architecture=%s' % ModelArchitectureNames.MOBILENET_V1,
+            '--output-stride=16',
+            '--source=%s' % EXAMPLE_IMAGE_URL,
+            '--output=%s' % output_image_path
+        ])

tf_bodypix/cli.py

@@ -5,6 +5,7 @@
 from abc import ABC, abstractmethod
 from contextlib import ExitStack
 from itertools import cycle
+from pathlib import Path
 from time import time
 from typing import Dict, List
 
@@ -25,8 +26,10 @@
 )
 from tf_bodypix.utils.s3 import iter_s3_file_urls
 from tf_bodypix.download import download_model
+from tf_bodypix.tflite import get_tflite_converter_for_model_path
 from tf_bodypix.model import (
     load_model,
+    VALID_MODEL_ARCHITECTURE_NAMES,
     PART_CHANNELS,
     DEFAULT_RESIZE_METHOD,
     BodyPixModelWrapper,
@@ -77,6 +80,14 @@ def add_model_arguments(parser: argparse.ArgumentParser):
         default=DEFAULT_MODEL_PATH,
         help="The path or URL to the bodypix model."
     )
+    parser.add_argument(
+        "--model-architecture",
+        choices=VALID_MODEL_ARCHITECTURE_NAMES,
+        help=(
+            "The model architecture."
+            " It will be guessed from the model path if not specified."
+        )
+    )
     parser.add_argument(
         "--output-stride",
         type=int,
@@ -219,7 +230,8 @@ def load_bodypix_model(args: argparse.Namespace) -> BodyPixModelWrapper:
     return load_model(
         local_model_path,
         internal_resolution=args.internal_resolution,
-        output_stride=args.output_stride
+        output_stride=args.output_stride,
+        architecture_name=args.model_architecture
     )
 
 
@@ -266,6 +278,52 @@ def run(self, args: argparse.Namespace):  # pylint: disable=unused-argument
         print('\n'.join(bodypix_model_json_files))
 
 
+class ConvertToTFLiteSubCommand(SubCommand):
+    def __init__(self):
+        super().__init__("convert-to-tflite", "Converts the model to a tflite model")
+
+    def add_arguments(self, parser: argparse.ArgumentParser):
+        add_common_arguments(parser)
+        parser.add_argument(
+            "--model-path",
+            default=DEFAULT_MODEL_PATH,
+            help="The path or URL to the bodypix model."
+        )
+        parser.add_argument(
+            "--output-model-file",
+            required=True,
+            help="The path to the output file (tflite model)."
+        )
+        parser.add_argument(
+            "--optimize",
+            action='store_true',
+            help="Enable optimization (quantization)."
+        )
+        parser.add_argument(
+            "--quantization-type",
+            choices=['float16', 'float32', 'int8'],
+            help="The quantization type to use."
+        )
+
+    def run(self, args: argparse.Namespace):  # pylint: disable=unused-argument
+        LOGGER.info('converting model: %s', args.model_path)
+        converter = get_tflite_converter_for_model_path(download_model(
+            args.model_path
+        ))
+        tflite_model = converter.convert()
+        if args.optimize:
+            LOGGER.info('enabled optimization')
+            converter.optimizations = [tf.lite.Optimize.DEFAULT]
+        if args.quantization_type:
+            LOGGER.info('quanization type: %s', args.quantization_type)
+            quantization_type = getattr(tf, args.quantization_type)
+            converter.target_spec.supported_types = [quantization_type]
+            converter.inference_input_type = quantization_type
+            converter.inference_output_type = quantization_type
+        LOGGER.info('saving tflite model to: %s', args.output_model_file)
+        Path(args.output_model_file).write_bytes(tflite_model)
+
+
 class AbstractWebcamFilterApp(ABC):
     def __init__(self, args: argparse.Namespace):
         self.args = args
@@ -497,6 +555,7 @@ def get_app(self, args: argparse.Namespace) -> AbstractWebcamFilterApp:
 
 SUB_COMMANDS: List[SubCommand] = [
     ListModelsSubCommand(),
+    ConvertToTFLiteSubCommand(),
     DrawMaskSubCommand(),
     BlurBackgroundSubCommand(),
     ReplaceBackgroundSubCommand()

tf_bodypix/model.py

@@ -341,6 +341,66 @@ def get_structured_output_names(structured_outputs: List[tf.Tensor]) -> List[str
     ]
 
 
+def to_number_of_dimensions(data: np.ndarray, dimension_count: int) -> np.ndarray:
+    while len(data.shape) > dimension_count:
+        data = data[0]
+    while len(data.shape) < dimension_count:
+        data = np.expand_dims(data, axis=0)
+    return data
+
+
+def load_tflite_model(model_path: str):
+    # Load TFLite model and allocate tensors.
+    interpreter = tf.lite.Interpreter(model_path=model_path)
+    interpreter.allocate_tensors()
+
+    input_details = interpreter.get_input_details()
+    LOGGER.debug('input_details: %s', input_details)
+    input_names = [item['name'] for item in input_details]
+    LOGGER.debug('input_names: %s', input_names)
+    input_details_map = dict(zip(input_names, input_details))
+
+    output_details = interpreter.get_output_details()
+    LOGGER.debug('output_details: %s', output_details)
+    output_names = [item['name'] for item in output_details]
+    LOGGER.debug('output_names: %s', output_names)
+
+    try:
+        image_input = input_details_map['image']
+    except KeyError:
+        assert len(input_details_map) == 1
+        image_input = list(input_details_map.values())[0]
+    input_shape = image_input['shape']
+    LOGGER.debug('input_shape: %s', input_shape)
+
+    def predict(image_data: np.ndarray):
+        nonlocal input_shape
+        image_data = to_number_of_dimensions(image_data, len(input_shape))
+        LOGGER.debug('tflite predict, image_data.shape=%s (%s)', image_data.shape, image_data.dtype)
+        height, width, *_ = image_data.shape
+        if tuple(image_data.shape) != tuple(input_shape):
+            LOGGER.info('resizing input tensor: %s -> %s', tuple(input_shape), image_data.shape)
+            interpreter.resize_tensor_input(image_input['index'], list(image_data.shape))
+            interpreter.allocate_tensors()
+            input_shape = image_data.shape
+        interpreter.set_tensor(image_input['index'], image_data)
+        if 'image_size' in input_details_map:
+            interpreter.set_tensor(
+                input_details_map['image_size']['index'],
+                np.array([height, width], dtype=np.float)
+            )
+
+        interpreter.invoke()
+
+        # The function `get_tensor()` returns a copy of the tensor data.
+        # Use `tensor()` in order to get a pointer to the tensor.
+        return {
+            item['name']: interpreter.get_tensor(item['index'])
+            for item in output_details
+        }
+    return predict
+
+
 def load_using_saved_model_and_get_predict_function(model_path):
     loaded = tf.saved_model.load(model_path)
     LOGGER.debug('loaded: %s', loaded)
@@ -366,24 +426,26 @@ def load_using_tfjs_graph_converter_and_get_predict_function(
 def load_model_and_get_predict_function(
     model_path: str
 ) -> Callable[[np.ndarray], dict]:
+    if model_path.endswith('.tflite'):
+        return load_tflite_model(model_path)
     try:
         return load_using_saved_model_and_get_predict_function(model_path)
     except OSError:
         return load_using_tfjs_graph_converter_and_get_predict_function(model_path)
 
 
 def get_output_stride_from_model_path(model_path: str) -> int:
-    match = re.search(r'stride(\d+)', model_path)
+    match = re.search(r'stride(\d+)|_(\d+)_quant', model_path)
     if not match:
         raise ValueError('cannot extract output stride from model path: %r' % model_path)
-    return int(match.group(1))
+    return int(match.group(1) or match.group(2))
 
 
 def get_architecture_from_model_path(model_path: str) -> int:
     model_path_lower = model_path.lower()
     if 'mobilenet' in model_path_lower:
         return ModelArchitectureNames.MOBILENET_V1
-    if 'resnet50' in model_path_lower:
+    if 'resnet' in model_path_lower:
         return ModelArchitectureNames.RESNET_50
     raise ValueError('cannot extract model architecture from model path: %r' % model_path)
 

tf_bodypix/tflite.py

@@ -0,0 +1,25 @@
+import logging
+
+import tensorflow as tf
+
+try:
+    import tfjs_graph_converter
+except ImportError:
+    tfjs_graph_converter = None
+
+
+LOGGER = logging.getLogger(__name__)
+
+
+def get_tflite_converter_for_tfjs_model_path(model_path: str) -> tf.lite.TFLiteConverter:
+    if tfjs_graph_converter is None:
+        raise ImportError('tfjs_graph_converter required')
+    graph = tfjs_graph_converter.api.load_graph_model(model_path)
+    tf_fn = tfjs_graph_converter.api.graph_to_function_v2(graph)
+    return tf.lite.TFLiteConverter.from_concrete_functions([tf_fn])
+
+
+def get_tflite_converter_for_model_path(model_path: str) -> tf.lite.TFLiteConverter:
+    LOGGER.debug('converting model_path: %s', model_path)
+    # if model_path.endswith('.json'):
+    return get_tflite_converter_for_tfjs_model_path(model_path)