Keras to TensorFlow

The keras_to_tensorflow.py is a tool that converts a trained keras model into a ready-for-inference TensorFlow model.

Summary

• In the default behaviour, this tool freezes the nodes (converts all TF variables to TF constants), and saves the inference graph and weights into a binary protobuf (.pb) file. During freezing, TensorFlow also applies node pruning which removes nodes with no contribution to the output tensor.

• This tool supports multiple output networks and enables the user to rename the output tensors via the --output_nodes_prefix flag.

• If the --output_meta_ckpt flag is set, the checkpoint and metagraph files for TensorFlow will also be exported which can later be used in the tf.train.Saver class to continue training.

How to use

Keras models can be saved as a single [.hdf5 or h5] file, which stores both the architecture and weights, using the model.save() function. This model can be then converted to a TensorFlow model by calling this tool as follows:

python keras_to_tensorflow.py 
    --input_model="path/to/keras/model.h5" 
    --output_model="path/to/save/model.pb"

Keras models can also be saved in two separate files where a [.hdf5 or h5] file stores the weights, using the model.save_weights() function, and another .json file stores the network architecture using the model.to_json() function. In this case, the model can be converted as follows:

python keras_to_tensorflow.py 
    --input_model="path/to/keras/model.h5" 
    --input_model_json="path/to/keras/model.json" 
    --output_model="path/to/save/model.pb"

Try

python keras_to_tensorflow.py --help

to learn about other supported flags (quantize, output_nodes_prefix, save_graph_def).

Dependencies

• keras
• tensorflow
• absl
• pathlib

Legacy code

The code on how to freeze and save keras models in previous versions of tensorflow is also available. Back then, the freeze_graph tool (/tensorflow/python/tools/freeze_graph.py) was used to convert the variables into constants. This functionality is now handled by graph_util.convert_variables_to_constants