Transfer learning and fine-tuning

1. Data Preprocessing

In this tutorial, you will use a dataset containing several thousand images of cats and dogs. Download and extract a zip file containing the images, then create a tf.data.Dataset for training and validation using the tf.keras.preprocessing.image_dataset_from_directory utility

_URL = 'https://storage.googleapis.com/mledu-datasets/cats_and_dogs_filtered.zip'
path_to_zip = tf.keras.utils.get_file('cats_and_dogs.zip', origin=_URL, extract=True)
PATH = os.path.join(os.path.dirname(path_to_zip), 'cats_and_dogs_filtered')

train_dir = os.path.join(PATH, 'train')
validation_dir = os.path.join(PATH, 'validation')

BATCH_SIZE = 32
IMG_SIZE = (160, 160)

train_dataset = image_dataset_from_directory(train_dir,
                                             shuffle=True,
                                             batch_size=BATCH_SIZE,
                                             image_size=IMG_SIZE)

validation_dataset = image_dataset_from_directory(validation_dir,                                                  shuffle=True,                                                  batch_size=BATCH_SIZE,                                                  image_size=IMG_SIZE)

2. Configure the dataset for performance

AUTOTUNE = tf.data.AUTOTUNEtrain_dataset = train_dataset.prefetch(buffer_size=AUTOTUNE)validation_dataset = validation_dataset.prefetch(buffer_size=AUTOTUNE)test_dataset = test_dataset.prefetch(buffer_size=AUTOTUNE)

3. Use data augmentation

data_augmentation = tf.keras.Sequential([  tf.keras.layers.experimental.preprocessing.RandomFlip('horizontal'),  tf.keras.layers.experimental.preprocessing.RandomRotation(0.2),])

4. Rescale pixel values

preprocess_input = tf.keras.applications.mobilenet_v2.preprocess_input

rescale = tf.keras.layers.experimental.preprocessing.Rescaling(1./127.5, offset= -1)

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