EfficientNetV2 models rewritten in Keras functional API.

Changelog:

• Feb 2022:
  • As of 2.8 Tensorflow release, the models in this repository (apart from XL variant) are accessible through keras.applications.efficientnet_v2
    You are free to use this repo or Keras directly.
• Nov 2021:
  • added more weights variants from original repo.
  • added option to manually get preprocessing layer.
• Sept. 2021 - Added XL model variant.
  • Changed layer naming convention.
  • Re-exported weights.

Table of contens

1. Introduction
2. Quickstart
3. Installation
4. How to use
5. Original Weights

Introduction

This is a package with EfficientNetV2 model variants adapted to Keras functional API. I rewrote them this way so that the usage is similar to keras.applications.

The model's weights are converted from original repository.

Quickstart

You can use these models, similar to keras.applications:

# Install
!pip install git+https://github.com/sebastian-sz/efficientnet-v2-keras@main

# Import package:
from efficientnet_v2 import EfficientNetV2S
import tensorflow as tf

# Use model directly:
model = EfficientNetV2S(
    weights='imagenet', input_shape=(384, 384, 3)
) 
model.summary()

# Or to extract features / fine tune:
backbone = EfficientNetV2S(
   weights='imagenet', 
   input_shape=(384, 384, 3),
   include_top=False
)

model = tf.keras.Sequential([
    backbone,
    tf.keras.layers.GlobalAveragePooling2D(),
    tf.keras.layers.Dense(10)  # 10 = num classes
])
model.compile(...)
model.fit(...)

You can fine tune these models, just like other Keras models.

For end-to-end fine-tuning and conversion examples check out the Colab Notebook.

Installation

There are multiple ways to install.
The only requirements are Tensorflow 2.2+ and Python 3.6+.
(Though, it is recommended to use at least Tensorflow 2.4)

Option A: (recommended) pip install from github

pip install git+https://github.com/sebastian-sz/efficientnet-v2-keras@main

Option B: Build from source

git clone https://github.com/sebastian-sz/efficientnet-v2-keras.git  
cd efficientnet-v2-keras  
pip install .

Option C: (alternatively) no install:

If you do not want to install you could just drop the efficientnet_v2/ directory, directly into your project.

Option D: Docker

You can also install this package as an extension to official Tensorflow docker container: Build: docker build -t efficientnet_v2_keras .
Run: docker run -it --rm efficientnet_v2_keras

For GPU support or different TAG you can (for example) pass
--build-arg IMAGE_TAG=2.5.0-gpu
in build command.

Verify installation

If all goes well you should be able to import:
from efficientnet_v2 import *

How to use

Pretrained weights

Weights converted from original repository will be automatically downloaded, once you pass weights="imagenet" (or imagenet-21k, imagenet-21k-ft1k) upon model creation.

There are 3 weight variants:

• imagenet - pretrained on Imagenet1k
• imagenet-21k - pretrained on Imagenet21k
• imagenet-21k-ft1k - pretrained on Imagenet21k and fine tuned on Imagenet1k

Note: imagenet weights have not been released for XL variant.

Input shapes

The variants expect the following input shapes.

Model variant	Input shape
B0	224,224
B1	240,240
B2	260,260
B3	300,300
S	384,384
M	480,480
L	480,480
XL	512,512

Preprocessing

Option A: preprocessing function

The preprocessing is different for Bx and S/M/L/XL variants. Bx's expect image normalized with Imagenet mean and stddev, while other's a simple rescale:

import tensorflow as tf

# Bx preprocessing:
def preprocess(image):  # input image is in range 0-255.
    mean_rgb = [0.485 * 255, 0.456 * 255, 0.406 * 255]
    stddev_rgb = [0.229 * 255, 0.224 * 255, 0.225 * 255]
    image -= tf.constant(mean_rgb, shape=(1, 1, 3), dtype=image.dtype)
    image /= tf.constant(stddev_rgb, shape=(1, 1, 3), dtype=image.dtype)
    return image
    
# S/M/L/XL preprocessing
def preprocess(image):  
    return (tf.cast(image, dtype=tf.float32) - 128.00) / 128.00

Option B: Preprocessing layers

or you can use Preprocessing Layer included in this repo:

from efficientnet_v2 import get_preprocessing_layer

preprocessing_layer = get_preprocessing_layer(variant="b0")

Fine-tuning

For fine-tuning example, check out the Colab Notebook.

Tensorflow Lite

The models are TFLite compatible. You can convert them like any other Keras model:

converter = tf.lite.TFLiteConverter.from_keras_model(model)
tflite_model = converter.convert()
with open("efficientnet_lite.tflite", "wb") as file:
  file.write(tflite_model)

ONNX

The models are ONNX compatible. For ONNX Conversion you can use tf2onnx package:

!pip install tf2onnx==1.8.4

# Save the model in TF's Saved Model format:
model.save("my_saved_model/")

# Convert:
!python -m tf2onnx.convert \
  --saved-model my_saved_model/ \
  --output efficientnet_v2.onnx

Original Weights

The original weights are present in the original repoistory. The original models were also trained using Keras are compatible with TF 2.

(Optionally) Convert the weights

The converted weights are on this repository's GitHub. If, for some reason, you wish to download and convert original weights yourself, I prepared the utility scripts:

1. bash scripts/download_all.sh
2. bash scripts/convert_all.sh

Bibliography

[1] Original repository

Closing words

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