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Keras Applications

Keras Applications are deep learning models that are made available alongside pre-trained weights. These models can be used for prediction, feature extraction, and fine-tuning.

Weights are downloaded automatically when instantiating a model. They are stored at ~/.keras/models/.

Upon instantiation, the models will be built according to the image data format set in your Keras configuration file at ~/.keras/keras.json. For instance, if you have set image_data_format=channels_last, then any model loaded from this repository will get built according to the TensorFlow data format convention, "Height-Width-Depth".

Available models

Model Size Top-1 Accuracy Top-5 Accuracy Parameters Depth
Xception 88 MB 0.790 0.945 22,910,480 126
VGG16 528 MB 0.713 0.901 138,357,544 23
VGG19 549 MB 0.713 0.900 143,667,240 26
ResNet50 98 MB 0.749 0.921 25,636,712 -
ResNet101 171 MB 0.764 0.928 44,707,176 -
ResNet152 232 MB 0.766 0.931 60,419,944 -
ResNet50V2 98 MB 0.760 0.930 25,613,800 -
ResNet101V2 171 MB 0.772 0.938 44,675,560 -
ResNet152V2 232 MB 0.780 0.942 60,380,648 -
InceptionV3 92 MB 0.779 0.937 23,851,784 159
InceptionResNetV2 215 MB 0.803 0.953 55,873,736 572
MobileNet 16 MB 0.704 0.895 4,253,864 88
MobileNetV2 14 MB 0.713 0.901 3,538,984 88
DenseNet121 33 MB 0.750 0.923 8,062,504 121
DenseNet169 57 MB 0.762 0.932 14,307,880 169
DenseNet201 80 MB 0.773 0.936 20,242,984 201
NASNetMobile 23 MB 0.744 0.919 5,326,716 -
NASNetLarge 343 MB 0.825 0.960 88,949,818 -
EfficientNetB0 29 MB - - 5,330,571 -
EfficientNetB1 31 MB - - 7,856,239 -
EfficientNetB2 36 MB - - 9,177,569 -
EfficientNetB3 48 MB - - 12,320,535 -
EfficientNetB4 75 MB - - 19,466,823 -
EfficientNetB5 118 MB - - 30,562,527 -
EfficientNetB6 166 MB - - 43,265,143 -
EfficientNetB7 256 MB - - 66,658,687 -


The top-1 and top-5 accuracy refers to the model's performance on the ImageNet validation dataset.

Depth refers to the topological depth of the network. This includes activation layers, batch normalization layers etc.


Usage examples for image classification models

Classify ImageNet classes with ResNet50

from tensorflow.keras.applications.resnet50 import ResNet50
from tensorflow.keras.preprocessing import image
from tensorflow.keras.applications.resnet50 import preprocess_input, decode_predictions
import numpy as np

model = ResNet50(weights='imagenet')

img_path = 'elephant.jpg'
img = image.load_img(img_path, target_size=(224, 224))
x = image.img_to_array(img)
x = np.expand_dims(x, axis=0)
x = preprocess_input(x)

preds = model.predict(x)
# decode the results into a list of tuples (class, description, probability)
# (one such list for each sample in the batch)
print('Predicted:', decode_predictions(preds, top=3)[0])
# Predicted: [(u'n02504013', u'Indian_elephant', 0.82658225), (u'n01871265', u'tusker', 0.1122357), (u'n02504458', u'African_elephant', 0.061040461)]

Extract features with VGG16

from tensorflow.keras.applications.vgg16 import VGG16
from tensorflow.keras.preprocessing import image
from tensorflow.keras.applications.vgg16 import preprocess_input
import numpy as np

model = VGG16(weights='imagenet', include_top=False)

img_path = 'elephant.jpg'
img = image.load_img(img_path, target_size=(224, 224))
x = image.img_to_array(img)
x = np.expand_dims(x, axis=0)
x = preprocess_input(x)

features = model.predict(x)

Extract features from an arbitrary intermediate layer with VGG19

from tensorflow.keras.applications.vgg19 import VGG19
from tensorflow.keras.preprocessing import image
from tensorflow.keras.applications.vgg19 import preprocess_input
from tensorflow.keras.models import Model
import numpy as np

base_model = VGG19(weights='imagenet')
model = Model(inputs=base_model.input, outputs=base_model.get_layer('block4_pool').output)

img_path = 'elephant.jpg'
img = image.load_img(img_path, target_size=(224, 224))
x = image.img_to_array(img)
x = np.expand_dims(x, axis=0)
x = preprocess_input(x)

block4_pool_features = model.predict(x)

Fine-tune InceptionV3 on a new set of classes

from tensorflow.keras.applications.inception_v3 import InceptionV3
from tensorflow.keras.preprocessing import image
from tensorflow.keras.models import Model
from tensorflow.keras.layers import Dense, GlobalAveragePooling2D

# create the base pre-trained model
base_model = InceptionV3(weights='imagenet', include_top=False)

# add a global spatial average pooling layer
x = base_model.output
x = GlobalAveragePooling2D()(x)
# let's add a fully-connected layer
x = Dense(1024, activation='relu')(x)
# and a logistic layer -- let's say we have 200 classes
predictions = Dense(200, activation='softmax')(x)

# this is the model we will train
model = Model(inputs=base_model.input, outputs=predictions)

# first: train only the top layers (which were randomly initialized)
# i.e. freeze all convolutional InceptionV3 layers
for layer in base_model.layers:
    layer.trainable = False

# compile the model (should be done *after* setting layers to non-trainable)
model.compile(optimizer='rmsprop', loss='categorical_crossentropy')

# train the model on the new data for a few epochs
model.fit(...)

# at this point, the top layers are well trained and we can start fine-tuning
# convolutional layers from inception V3. We will freeze the bottom N layers
# and train the remaining top layers.

# let's visualize layer names and layer indices to see how many layers
# we should freeze:
for i, layer in enumerate(base_model.layers):
   print(i, layer.name)

# we chose to train the top 2 inception blocks, i.e. we will freeze
# the first 249 layers and unfreeze the rest:
for layer in model.layers[:249]:
   layer.trainable = False
for layer in model.layers[249:]:
   layer.trainable = True

# we need to recompile the model for these modifications to take effect
# we use SGD with a low learning rate
from tensorflow.keras.optimizers import SGD
model.compile(optimizer=SGD(lr=0.0001, momentum=0.9), loss='categorical_crossentropy')

# we train our model again (this time fine-tuning the top 2 inception blocks
# alongside the top Dense layers
model.fit(...)

Build InceptionV3 over a custom input tensor

from tensorflow.keras.applications.inception_v3 import InceptionV3
from tensorflow.keras.layers import Input

# this could also be the output a different Keras model or layer
input_tensor = Input(shape=(224, 224, 3))

model = InceptionV3(input_tensor=input_tensor, weights='imagenet', include_top=True)