Module keras.applications.mobilenet_v2
MobileNet v2 models for Keras.
MobileNetV2 is a general architecture and can be used for multiple use cases. Depending on the use case, it can use different input layer size and different width factors. This allows different width models to reduce the number of multiply-adds and thereby reduce inference cost on mobile devices.
MobileNetV2 is very similar to the original MobileNet, except that it uses inverted residual blocks with bottlenecking features. It has a drastically lower parameter count than the original MobileNet. MobileNets support any input size greater than 32 x 32, with larger image sizes offering better performance.
The number of parameters and number of multiply-adds
can be modified by using the alpha
parameter,
which increases/decreases the number of filters in each layer.
By altering the image size and alpha
parameter,
all 22 models from the paper can be built, with ImageNet weights provided.
The paper demonstrates the performance of MobileNets using alpha
values of
1.0 (also called 100 % MobileNet), 0.35, 0.5, 0.75, 1.0, 1.3, and 1.4
For each of these alpha
values, weights for 5 different input image sizes
are provided (224, 192, 160, 128, and 96).
The following table describes the performance of MobileNet on various input sizes:
MACs stands for Multiply Adds Classification Checkpoint|MACs (M)|Parameters (M)|Top 1 Accuracy|Top 5 Accuracy --------------------------|------------|---------------|---------|----|--------- | [mobilenet_v2_1.4_224] | 582 | 6.06 | 75.0 | 92.5 | | [mobilenet_v2_1.3_224] | 509 | 5.34 | 74.4 | 92.1 | | [mobilenet_v2_1.0_224] | 300 | 3.47 | 71.8 | 91.0 | | [mobilenet_v2_1.0_192] | 221 | 3.47 | 70.7 | 90.1 | | [mobilenet_v2_1.0_160] | 154 | 3.47 | 68.8 | 89.0 | | [mobilenet_v2_1.0_128] | 99 | 3.47 | 65.3 | 86.9 | | [mobilenet_v2_1.0_96] | 56 | 3.47 | 60.3 | 83.2 | | [mobilenet_v2_0.75_224] | 209 | 2.61 | 69.8 | 89.6 | | [mobilenet_v2_0.75_192] | 153 | 2.61 | 68.7 | 88.9 | | [mobilenet_v2_0.75_160] | 107 | 2.61 | 66.4 | 87.3 | | [mobilenet_v2_0.75_128] | 69 | 2.61 | 63.2 | 85.3 | | [mobilenet_v2_0.75_96] | 39 | 2.61 | 58.8 | 81.6 | | [mobilenet_v2_0.5_224] | 97 | 1.95 | 65.4 | 86.4 | | [mobilenet_v2_0.5_192] | 71 | 1.95 | 63.9 | 85.4 | | [mobilenet_v2_0.5_160] | 50 | 1.95 | 61.0 | 83.2 | | [mobilenet_v2_0.5_128] | 32 | 1.95 | 57.7 | 80.8 | | [mobilenet_v2_0.5_96] | 18 | 1.95 | 51.2 | 75.8 | | [mobilenet_v2_0.35_224] | 59 | 1.66 | 60.3 | 82.9 | | [mobilenet_v2_0.35_192] | 43 | 1.66 | 58.2 | 81.2 | | [mobilenet_v2_0.35_160] | 30 | 1.66 | 55.7 | 79.1 | | [mobilenet_v2_0.35_128] | 20 | 1.66 | 50.8 | 75.0 | | [mobilenet_v2_0.35_96] | 11 | 1.66 | 45.5 | 70.4 |
Reference: - MobileNetV2: Inverted Residuals and Linear Bottlenecks (CVPR 2018)
Expand source code
# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
# pylint: disable=invalid-name
"""MobileNet v2 models for Keras.
MobileNetV2 is a general architecture and can be used for multiple use cases.
Depending on the use case, it can use different input layer size and
different width factors. This allows different width models to reduce
the number of multiply-adds and thereby
reduce inference cost on mobile devices.
MobileNetV2 is very similar to the original MobileNet,
except that it uses inverted residual blocks with
bottlenecking features. It has a drastically lower
parameter count than the original MobileNet.
MobileNets support any input size greater
than 32 x 32, with larger image sizes
offering better performance.
The number of parameters and number of multiply-adds
can be modified by using the `alpha` parameter,
which increases/decreases the number of filters in each layer.
By altering the image size and `alpha` parameter,
all 22 models from the paper can be built, with ImageNet weights provided.
The paper demonstrates the performance of MobileNets using `alpha` values of
1.0 (also called 100 % MobileNet), 0.35, 0.5, 0.75, 1.0, 1.3, and 1.4
For each of these `alpha` values, weights for 5 different input image sizes
are provided (224, 192, 160, 128, and 96).
The following table describes the performance of
MobileNet on various input sizes:
------------------------------------------------------------------------
MACs stands for Multiply Adds
Classification Checkpoint|MACs (M)|Parameters (M)|Top 1 Accuracy|Top 5 Accuracy
--------------------------|------------|---------------|---------|----|---------
| [mobilenet_v2_1.4_224] | 582 | 6.06 | 75.0 | 92.5 |
| [mobilenet_v2_1.3_224] | 509 | 5.34 | 74.4 | 92.1 |
| [mobilenet_v2_1.0_224] | 300 | 3.47 | 71.8 | 91.0 |
| [mobilenet_v2_1.0_192] | 221 | 3.47 | 70.7 | 90.1 |
| [mobilenet_v2_1.0_160] | 154 | 3.47 | 68.8 | 89.0 |
| [mobilenet_v2_1.0_128] | 99 | 3.47 | 65.3 | 86.9 |
| [mobilenet_v2_1.0_96] | 56 | 3.47 | 60.3 | 83.2 |
| [mobilenet_v2_0.75_224] | 209 | 2.61 | 69.8 | 89.6 |
| [mobilenet_v2_0.75_192] | 153 | 2.61 | 68.7 | 88.9 |
| [mobilenet_v2_0.75_160] | 107 | 2.61 | 66.4 | 87.3 |
| [mobilenet_v2_0.75_128] | 69 | 2.61 | 63.2 | 85.3 |
| [mobilenet_v2_0.75_96] | 39 | 2.61 | 58.8 | 81.6 |
| [mobilenet_v2_0.5_224] | 97 | 1.95 | 65.4 | 86.4 |
| [mobilenet_v2_0.5_192] | 71 | 1.95 | 63.9 | 85.4 |
| [mobilenet_v2_0.5_160] | 50 | 1.95 | 61.0 | 83.2 |
| [mobilenet_v2_0.5_128] | 32 | 1.95 | 57.7 | 80.8 |
| [mobilenet_v2_0.5_96] | 18 | 1.95 | 51.2 | 75.8 |
| [mobilenet_v2_0.35_224] | 59 | 1.66 | 60.3 | 82.9 |
| [mobilenet_v2_0.35_192] | 43 | 1.66 | 58.2 | 81.2 |
| [mobilenet_v2_0.35_160] | 30 | 1.66 | 55.7 | 79.1 |
| [mobilenet_v2_0.35_128] | 20 | 1.66 | 50.8 | 75.0 |
| [mobilenet_v2_0.35_96] | 11 | 1.66 | 45.5 | 70.4 |
Reference:
- [MobileNetV2: Inverted Residuals and Linear Bottlenecks](
https://arxiv.org/abs/1801.04381) (CVPR 2018)
"""
import tensorflow.compat.v2 as tf
from keras import backend
from keras.applications import imagenet_utils
from keras.engine import training
from keras.layers import VersionAwareLayers
from keras.utils import data_utils
from keras.utils import layer_utils
from tensorflow.python.platform import tf_logging as logging
from tensorflow.python.util.tf_export import keras_export
BASE_WEIGHT_PATH = ('https://storage.googleapis.com/tensorflow/'
'keras-applications/mobilenet_v2/')
layers = None
@keras_export('keras.applications.mobilenet_v2.MobileNetV2',
'keras.applications.MobileNetV2')
def MobileNetV2(input_shape=None,
alpha=1.0,
include_top=True,
weights='imagenet',
input_tensor=None,
pooling=None,
classes=1000,
classifier_activation='softmax',
**kwargs):
"""Instantiates the MobileNetV2 architecture.
MobileNetV2 is very similar to the original MobileNet,
except that it uses inverted residual blocks with
bottlenecking features. It has a drastically lower
parameter count than the original MobileNet.
MobileNets support any input size greater
than 32 x 32, with larger image sizes
offering better performance.
Reference:
- [MobileNetV2: Inverted Residuals and Linear Bottlenecks](
https://arxiv.org/abs/1801.04381) (CVPR 2018)
This function returns a Keras image classification model,
optionally loaded with weights pre-trained on ImageNet.
For image classification use cases, see
[this page for detailed examples](
https://keras.io/api/applications/#usage-examples-for-image-classification-models).
For transfer learning use cases, make sure to read the
[guide to transfer learning & fine-tuning](
https://keras.io/guides/transfer_learning/).
Note: each Keras Application expects a specific kind of input preprocessing.
For MobileNetV2, call `tf.keras.applications.mobilenet_v2.preprocess_input`
on your inputs before passing them to the model.
`mobilenet_v2.preprocess_input` will scale input pixels between -1 and 1.
Args:
input_shape: Optional shape tuple, to be specified if you would
like to use a model with an input image resolution that is not
(224, 224, 3).
It should have exactly 3 inputs channels (224, 224, 3).
You can also omit this option if you would like
to infer input_shape from an input_tensor.
If you choose to include both input_tensor and input_shape then
input_shape will be used if they match, if the shapes
do not match then we will throw an error.
E.g. `(160, 160, 3)` would be one valid value.
alpha: Float between 0 and 1. controls the width of the network.
This is known as the width multiplier in the MobileNetV2 paper,
but the name is kept for consistency with `applications.MobileNetV1`
model in Keras.
- If `alpha` < 1.0, proportionally decreases the number
of filters in each layer.
- If `alpha` > 1.0, proportionally increases the number
of filters in each layer.
- If `alpha` = 1.0, default number of filters from the paper
are used at each layer.
include_top: Boolean, whether to include the fully-connected
layer at the top of the network. Defaults to `True`.
weights: String, one of `None` (random initialization),
'imagenet' (pre-training on ImageNet),
or the path to the weights file to be loaded.
input_tensor: Optional Keras tensor (i.e. output of
`layers.Input()`)
to use as image input for the model.
pooling: String, optional pooling mode for feature extraction
when `include_top` is `False`.
- `None` means that the output of the model
will be the 4D tensor output of the
last convolutional block.
- `avg` means that global average pooling
will be applied to the output of the
last convolutional block, and thus
the output of the model will be a
2D tensor.
- `max` means that global max pooling will
be applied.
classes: Integer, optional number of classes to classify images
into, only to be specified if `include_top` is True, and
if no `weights` argument is specified.
classifier_activation: A `str` or callable. The activation function to use
on the "top" layer. Ignored unless `include_top=True`. Set
`classifier_activation=None` to return the logits of the "top" layer.
When loading pretrained weights, `classifier_activation` can only
be `None` or `"softmax"`.
**kwargs: For backwards compatibility only.
Returns:
A `keras.Model` instance.
"""
global layers
if 'layers' in kwargs:
layers = kwargs.pop('layers')
else:
layers = VersionAwareLayers()
if kwargs:
raise ValueError('Unknown argument(s): %s' % (kwargs,))
if not (weights in {'imagenet', None} or tf.io.gfile.exists(weights)):
raise ValueError('The `weights` argument should be either '
'`None` (random initialization), `imagenet` '
'(pre-training on ImageNet), '
'or the path to the weights file to be loaded.')
if weights == 'imagenet' and include_top and classes != 1000:
raise ValueError('If using `weights` as `"imagenet"` with `include_top` '
'as true, `classes` should be 1000')
# Determine proper input shape and default size.
# If both input_shape and input_tensor are used, they should match
if input_shape is not None and input_tensor is not None:
try:
is_input_t_tensor = backend.is_keras_tensor(input_tensor)
except ValueError:
try:
is_input_t_tensor = backend.is_keras_tensor(
layer_utils.get_source_inputs(input_tensor))
except ValueError:
raise ValueError('input_tensor: ', input_tensor,
'is not type input_tensor')
if is_input_t_tensor:
if backend.image_data_format() == 'channels_first':
if backend.int_shape(input_tensor)[1] != input_shape[1]:
raise ValueError('input_shape: ', input_shape, 'and input_tensor: ',
input_tensor,
'do not meet the same shape requirements')
else:
if backend.int_shape(input_tensor)[2] != input_shape[1]:
raise ValueError('input_shape: ', input_shape, 'and input_tensor: ',
input_tensor,
'do not meet the same shape requirements')
else:
raise ValueError('input_tensor specified: ', input_tensor,
'is not a keras tensor')
# If input_shape is None, infer shape from input_tensor
if input_shape is None and input_tensor is not None:
try:
backend.is_keras_tensor(input_tensor)
except ValueError:
raise ValueError('input_tensor: ', input_tensor, 'is type: ',
type(input_tensor), 'which is not a valid type')
if input_shape is None and not backend.is_keras_tensor(input_tensor):
default_size = 224
elif input_shape is None and backend.is_keras_tensor(input_tensor):
if backend.image_data_format() == 'channels_first':
rows = backend.int_shape(input_tensor)[2]
cols = backend.int_shape(input_tensor)[3]
else:
rows = backend.int_shape(input_tensor)[1]
cols = backend.int_shape(input_tensor)[2]
if rows == cols and rows in [96, 128, 160, 192, 224]:
default_size = rows
else:
default_size = 224
# If input_shape is None and no input_tensor
elif input_shape is None:
default_size = 224
# If input_shape is not None, assume default size
else:
if backend.image_data_format() == 'channels_first':
rows = input_shape[1]
cols = input_shape[2]
else:
rows = input_shape[0]
cols = input_shape[1]
if rows == cols and rows in [96, 128, 160, 192, 224]:
default_size = rows
else:
default_size = 224
input_shape = imagenet_utils.obtain_input_shape(
input_shape,
default_size=default_size,
min_size=32,
data_format=backend.image_data_format(),
require_flatten=include_top,
weights=weights)
if backend.image_data_format() == 'channels_last':
row_axis, col_axis = (0, 1)
else:
row_axis, col_axis = (1, 2)
rows = input_shape[row_axis]
cols = input_shape[col_axis]
if weights == 'imagenet':
if alpha not in [0.35, 0.50, 0.75, 1.0, 1.3, 1.4]:
raise ValueError('If imagenet weights are being loaded, '
'alpha can be one of `0.35`, `0.50`, `0.75`, '
'`1.0`, `1.3` or `1.4` only.')
if rows != cols or rows not in [96, 128, 160, 192, 224]:
rows = 224
logging.warning('`input_shape` is undefined or non-square, '
'or `rows` is not in [96, 128, 160, 192, 224].'
' Weights for input shape (224, 224) will be'
' loaded as the default.')
if input_tensor is None:
img_input = layers.Input(shape=input_shape)
else:
if not backend.is_keras_tensor(input_tensor):
img_input = layers.Input(tensor=input_tensor, shape=input_shape)
else:
img_input = input_tensor
channel_axis = 1 if backend.image_data_format() == 'channels_first' else -1
first_block_filters = _make_divisible(32 * alpha, 8)
x = layers.Conv2D(
first_block_filters,
kernel_size=3,
strides=(2, 2),
padding='same',
use_bias=False,
name='Conv1')(img_input)
x = layers.BatchNormalization(
axis=channel_axis, epsilon=1e-3, momentum=0.999, name='bn_Conv1')(
x)
x = layers.ReLU(6., name='Conv1_relu')(x)
x = _inverted_res_block(
x, filters=16, alpha=alpha, stride=1, expansion=1, block_id=0)
x = _inverted_res_block(
x, filters=24, alpha=alpha, stride=2, expansion=6, block_id=1)
x = _inverted_res_block(
x, filters=24, alpha=alpha, stride=1, expansion=6, block_id=2)
x = _inverted_res_block(
x, filters=32, alpha=alpha, stride=2, expansion=6, block_id=3)
x = _inverted_res_block(
x, filters=32, alpha=alpha, stride=1, expansion=6, block_id=4)
x = _inverted_res_block(
x, filters=32, alpha=alpha, stride=1, expansion=6, block_id=5)
x = _inverted_res_block(
x, filters=64, alpha=alpha, stride=2, expansion=6, block_id=6)
x = _inverted_res_block(
x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=7)
x = _inverted_res_block(
x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=8)
x = _inverted_res_block(
x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=9)
x = _inverted_res_block(
x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=10)
x = _inverted_res_block(
x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=11)
x = _inverted_res_block(
x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=12)
x = _inverted_res_block(
x, filters=160, alpha=alpha, stride=2, expansion=6, block_id=13)
x = _inverted_res_block(
x, filters=160, alpha=alpha, stride=1, expansion=6, block_id=14)
x = _inverted_res_block(
x, filters=160, alpha=alpha, stride=1, expansion=6, block_id=15)
x = _inverted_res_block(
x, filters=320, alpha=alpha, stride=1, expansion=6, block_id=16)
# no alpha applied to last conv as stated in the paper:
# if the width multiplier is greater than 1 we
# increase the number of output channels
if alpha > 1.0:
last_block_filters = _make_divisible(1280 * alpha, 8)
else:
last_block_filters = 1280
x = layers.Conv2D(
last_block_filters, kernel_size=1, use_bias=False, name='Conv_1')(
x)
x = layers.BatchNormalization(
axis=channel_axis, epsilon=1e-3, momentum=0.999, name='Conv_1_bn')(
x)
x = layers.ReLU(6., name='out_relu')(x)
if include_top:
x = layers.GlobalAveragePooling2D()(x)
imagenet_utils.validate_activation(classifier_activation, weights)
x = layers.Dense(classes, activation=classifier_activation,
name='predictions')(x)
else:
if pooling == 'avg':
x = layers.GlobalAveragePooling2D()(x)
elif pooling == 'max':
x = layers.GlobalMaxPooling2D()(x)
# Ensure that the model takes into account
# any potential predecessors of `input_tensor`.
if input_tensor is not None:
inputs = layer_utils.get_source_inputs(input_tensor)
else:
inputs = img_input
# Create model.
model = training.Model(inputs, x, name='mobilenetv2_%0.2f_%s' % (alpha, rows))
# Load weights.
if weights == 'imagenet':
if include_top:
model_name = ('mobilenet_v2_weights_tf_dim_ordering_tf_kernels_' +
str(float(alpha)) + '_' + str(rows) + '.h5')
weight_path = BASE_WEIGHT_PATH + model_name
weights_path = data_utils.get_file(
model_name, weight_path, cache_subdir='models')
else:
model_name = ('mobilenet_v2_weights_tf_dim_ordering_tf_kernels_' +
str(float(alpha)) + '_' + str(rows) + '_no_top' + '.h5')
weight_path = BASE_WEIGHT_PATH + model_name
weights_path = data_utils.get_file(
model_name, weight_path, cache_subdir='models')
model.load_weights(weights_path)
elif weights is not None:
model.load_weights(weights)
return model
def _inverted_res_block(inputs, expansion, stride, alpha, filters, block_id):
"""Inverted ResNet block."""
channel_axis = 1 if backend.image_data_format() == 'channels_first' else -1
in_channels = backend.int_shape(inputs)[channel_axis]
pointwise_conv_filters = int(filters * alpha)
pointwise_filters = _make_divisible(pointwise_conv_filters, 8)
x = inputs
prefix = 'block_{}_'.format(block_id)
if block_id:
# Expand
x = layers.Conv2D(
expansion * in_channels,
kernel_size=1,
padding='same',
use_bias=False,
activation=None,
name=prefix + 'expand')(
x)
x = layers.BatchNormalization(
axis=channel_axis,
epsilon=1e-3,
momentum=0.999,
name=prefix + 'expand_BN')(
x)
x = layers.ReLU(6., name=prefix + 'expand_relu')(x)
else:
prefix = 'expanded_conv_'
# Depthwise
if stride == 2:
x = layers.ZeroPadding2D(
padding=imagenet_utils.correct_pad(x, 3),
name=prefix + 'pad')(x)
x = layers.DepthwiseConv2D(
kernel_size=3,
strides=stride,
activation=None,
use_bias=False,
padding='same' if stride == 1 else 'valid',
name=prefix + 'depthwise')(
x)
x = layers.BatchNormalization(
axis=channel_axis,
epsilon=1e-3,
momentum=0.999,
name=prefix + 'depthwise_BN')(
x)
x = layers.ReLU(6., name=prefix + 'depthwise_relu')(x)
# Project
x = layers.Conv2D(
pointwise_filters,
kernel_size=1,
padding='same',
use_bias=False,
activation=None,
name=prefix + 'project')(
x)
x = layers.BatchNormalization(
axis=channel_axis,
epsilon=1e-3,
momentum=0.999,
name=prefix + 'project_BN')(
x)
if in_channels == pointwise_filters and stride == 1:
return layers.Add(name=prefix + 'add')([inputs, x])
return x
def _make_divisible(v, divisor, min_value=None):
if min_value is None:
min_value = divisor
new_v = max(min_value, int(v + divisor / 2) // divisor * divisor)
# Make sure that round down does not go down by more than 10%.
if new_v < 0.9 * v:
new_v += divisor
return new_v
@keras_export('keras.applications.mobilenet_v2.preprocess_input')
def preprocess_input(x, data_format=None):
return imagenet_utils.preprocess_input(x, data_format=data_format, mode='tf')
@keras_export('keras.applications.mobilenet_v2.decode_predictions')
def decode_predictions(preds, top=5):
return imagenet_utils.decode_predictions(preds, top=top)
preprocess_input.__doc__ = imagenet_utils.PREPROCESS_INPUT_DOC.format(
mode='',
ret=imagenet_utils.PREPROCESS_INPUT_RET_DOC_TF,
error=imagenet_utils.PREPROCESS_INPUT_ERROR_DOC)
decode_predictions.__doc__ = imagenet_utils.decode_predictions.__doc__
Functions
def MobileNetV2(input_shape=None, alpha=1.0, include_top=True, weights='imagenet', input_tensor=None, pooling=None, classes=1000, classifier_activation='softmax', **kwargs)
-
Instantiates the MobileNetV2 architecture.
MobileNetV2 is very similar to the original MobileNet, except that it uses inverted residual blocks with bottlenecking features. It has a drastically lower parameter count than the original MobileNet. MobileNets support any input size greater than 32 x 32, with larger image sizes offering better performance.
Reference: - MobileNetV2: Inverted Residuals and Linear Bottlenecks (CVPR 2018)
This function returns a Keras image classification model, optionally loaded with weights pre-trained on ImageNet.
For image classification use cases, see this page for detailed examples.
For transfer learning use cases, make sure to read the guide to transfer learning & fine-tuning.
Note: each Keras Application expects a specific kind of input preprocessing. For MobileNetV2, call
tf.keras.applications.mobilenet_v2.preprocess_input
on your inputs before passing them to the model.mobilenet_v2.preprocess_input
will scale input pixels between -1 and 1.Args
input_shape
- Optional shape tuple, to be specified if you would
like to use a model with an input image resolution that is not
(224, 224, 3).
It should have exactly 3 inputs channels (224, 224, 3).
You can also omit this option if you would like
to infer input_shape from an input_tensor.
If you choose to include both input_tensor and input_shape then
input_shape will be used if they match, if the shapes
do not match then we will throw an error.
E.g.
(160, 160, 3)
would be one valid value. alpha
- Float between 0 and 1. controls the width of the network.
This is known as the width multiplier in the MobileNetV2 paper,
but the name is kept for consistency with
applications.MobileNetV1
model in Keras. - Ifalpha
< 1.0, proportionally decreases the number of filters in each layer. - Ifalpha
> 1.0, proportionally increases the number of filters in each layer. - Ifalpha
= 1.0, default number of filters from the paper are used at each layer. include_top
- Boolean, whether to include the fully-connected
layer at the top of the network. Defaults to
True
. weights
- String, one of
None
(random initialization), 'imagenet' (pre-training on ImageNet), or the path to the weights file to be loaded. input_tensor
- Optional Keras tensor (i.e. output of
layers.Input()
) to use as image input for the model. pooling
- String, optional pooling mode for feature extraction
when
include_top
isFalse
. -None
means that the output of the model will be the 4D tensor output of the last convolutional block. -avg
means that global average pooling will be applied to the output of the last convolutional block, and thus the output of the model will be a 2D tensor. -max
means that global max pooling will be applied. classes
- Integer, optional number of classes to classify images
into, only to be specified if
include_top
is True, and if noweights
argument is specified. classifier_activation
- A
str
or callable. The activation function to use on the "top" layer. Ignored unlessinclude_top=True
. Setclassifier_activation=None
to return the logits of the "top" layer. When loading pretrained weights,classifier_activation
can only beNone
or"softmax"
. **kwargs
- For backwards compatibility only.
Returns
A
keras.Model
instance.Expand source code
@keras_export('keras.applications.mobilenet_v2.MobileNetV2', 'keras.applications.MobileNetV2') def MobileNetV2(input_shape=None, alpha=1.0, include_top=True, weights='imagenet', input_tensor=None, pooling=None, classes=1000, classifier_activation='softmax', **kwargs): """Instantiates the MobileNetV2 architecture. MobileNetV2 is very similar to the original MobileNet, except that it uses inverted residual blocks with bottlenecking features. It has a drastically lower parameter count than the original MobileNet. MobileNets support any input size greater than 32 x 32, with larger image sizes offering better performance. Reference: - [MobileNetV2: Inverted Residuals and Linear Bottlenecks]( https://arxiv.org/abs/1801.04381) (CVPR 2018) This function returns a Keras image classification model, optionally loaded with weights pre-trained on ImageNet. For image classification use cases, see [this page for detailed examples]( https://keras.io/api/applications/#usage-examples-for-image-classification-models). For transfer learning use cases, make sure to read the [guide to transfer learning & fine-tuning]( https://keras.io/guides/transfer_learning/). Note: each Keras Application expects a specific kind of input preprocessing. For MobileNetV2, call `tf.keras.applications.mobilenet_v2.preprocess_input` on your inputs before passing them to the model. `mobilenet_v2.preprocess_input` will scale input pixels between -1 and 1. Args: input_shape: Optional shape tuple, to be specified if you would like to use a model with an input image resolution that is not (224, 224, 3). It should have exactly 3 inputs channels (224, 224, 3). You can also omit this option if you would like to infer input_shape from an input_tensor. If you choose to include both input_tensor and input_shape then input_shape will be used if they match, if the shapes do not match then we will throw an error. E.g. `(160, 160, 3)` would be one valid value. alpha: Float between 0 and 1. controls the width of the network. This is known as the width multiplier in the MobileNetV2 paper, but the name is kept for consistency with `applications.MobileNetV1` model in Keras. - If `alpha` < 1.0, proportionally decreases the number of filters in each layer. - If `alpha` > 1.0, proportionally increases the number of filters in each layer. - If `alpha` = 1.0, default number of filters from the paper are used at each layer. include_top: Boolean, whether to include the fully-connected layer at the top of the network. Defaults to `True`. weights: String, one of `None` (random initialization), 'imagenet' (pre-training on ImageNet), or the path to the weights file to be loaded. input_tensor: Optional Keras tensor (i.e. output of `layers.Input()`) to use as image input for the model. pooling: String, optional pooling mode for feature extraction when `include_top` is `False`. - `None` means that the output of the model will be the 4D tensor output of the last convolutional block. - `avg` means that global average pooling will be applied to the output of the last convolutional block, and thus the output of the model will be a 2D tensor. - `max` means that global max pooling will be applied. classes: Integer, optional number of classes to classify images into, only to be specified if `include_top` is True, and if no `weights` argument is specified. classifier_activation: A `str` or callable. The activation function to use on the "top" layer. Ignored unless `include_top=True`. Set `classifier_activation=None` to return the logits of the "top" layer. When loading pretrained weights, `classifier_activation` can only be `None` or `"softmax"`. **kwargs: For backwards compatibility only. Returns: A `keras.Model` instance. """ global layers if 'layers' in kwargs: layers = kwargs.pop('layers') else: layers = VersionAwareLayers() if kwargs: raise ValueError('Unknown argument(s): %s' % (kwargs,)) if not (weights in {'imagenet', None} or tf.io.gfile.exists(weights)): raise ValueError('The `weights` argument should be either ' '`None` (random initialization), `imagenet` ' '(pre-training on ImageNet), ' 'or the path to the weights file to be loaded.') if weights == 'imagenet' and include_top and classes != 1000: raise ValueError('If using `weights` as `"imagenet"` with `include_top` ' 'as true, `classes` should be 1000') # Determine proper input shape and default size. # If both input_shape and input_tensor are used, they should match if input_shape is not None and input_tensor is not None: try: is_input_t_tensor = backend.is_keras_tensor(input_tensor) except ValueError: try: is_input_t_tensor = backend.is_keras_tensor( layer_utils.get_source_inputs(input_tensor)) except ValueError: raise ValueError('input_tensor: ', input_tensor, 'is not type input_tensor') if is_input_t_tensor: if backend.image_data_format() == 'channels_first': if backend.int_shape(input_tensor)[1] != input_shape[1]: raise ValueError('input_shape: ', input_shape, 'and input_tensor: ', input_tensor, 'do not meet the same shape requirements') else: if backend.int_shape(input_tensor)[2] != input_shape[1]: raise ValueError('input_shape: ', input_shape, 'and input_tensor: ', input_tensor, 'do not meet the same shape requirements') else: raise ValueError('input_tensor specified: ', input_tensor, 'is not a keras tensor') # If input_shape is None, infer shape from input_tensor if input_shape is None and input_tensor is not None: try: backend.is_keras_tensor(input_tensor) except ValueError: raise ValueError('input_tensor: ', input_tensor, 'is type: ', type(input_tensor), 'which is not a valid type') if input_shape is None and not backend.is_keras_tensor(input_tensor): default_size = 224 elif input_shape is None and backend.is_keras_tensor(input_tensor): if backend.image_data_format() == 'channels_first': rows = backend.int_shape(input_tensor)[2] cols = backend.int_shape(input_tensor)[3] else: rows = backend.int_shape(input_tensor)[1] cols = backend.int_shape(input_tensor)[2] if rows == cols and rows in [96, 128, 160, 192, 224]: default_size = rows else: default_size = 224 # If input_shape is None and no input_tensor elif input_shape is None: default_size = 224 # If input_shape is not None, assume default size else: if backend.image_data_format() == 'channels_first': rows = input_shape[1] cols = input_shape[2] else: rows = input_shape[0] cols = input_shape[1] if rows == cols and rows in [96, 128, 160, 192, 224]: default_size = rows else: default_size = 224 input_shape = imagenet_utils.obtain_input_shape( input_shape, default_size=default_size, min_size=32, data_format=backend.image_data_format(), require_flatten=include_top, weights=weights) if backend.image_data_format() == 'channels_last': row_axis, col_axis = (0, 1) else: row_axis, col_axis = (1, 2) rows = input_shape[row_axis] cols = input_shape[col_axis] if weights == 'imagenet': if alpha not in [0.35, 0.50, 0.75, 1.0, 1.3, 1.4]: raise ValueError('If imagenet weights are being loaded, ' 'alpha can be one of `0.35`, `0.50`, `0.75`, ' '`1.0`, `1.3` or `1.4` only.') if rows != cols or rows not in [96, 128, 160, 192, 224]: rows = 224 logging.warning('`input_shape` is undefined or non-square, ' 'or `rows` is not in [96, 128, 160, 192, 224].' ' Weights for input shape (224, 224) will be' ' loaded as the default.') if input_tensor is None: img_input = layers.Input(shape=input_shape) else: if not backend.is_keras_tensor(input_tensor): img_input = layers.Input(tensor=input_tensor, shape=input_shape) else: img_input = input_tensor channel_axis = 1 if backend.image_data_format() == 'channels_first' else -1 first_block_filters = _make_divisible(32 * alpha, 8) x = layers.Conv2D( first_block_filters, kernel_size=3, strides=(2, 2), padding='same', use_bias=False, name='Conv1')(img_input) x = layers.BatchNormalization( axis=channel_axis, epsilon=1e-3, momentum=0.999, name='bn_Conv1')( x) x = layers.ReLU(6., name='Conv1_relu')(x) x = _inverted_res_block( x, filters=16, alpha=alpha, stride=1, expansion=1, block_id=0) x = _inverted_res_block( x, filters=24, alpha=alpha, stride=2, expansion=6, block_id=1) x = _inverted_res_block( x, filters=24, alpha=alpha, stride=1, expansion=6, block_id=2) x = _inverted_res_block( x, filters=32, alpha=alpha, stride=2, expansion=6, block_id=3) x = _inverted_res_block( x, filters=32, alpha=alpha, stride=1, expansion=6, block_id=4) x = _inverted_res_block( x, filters=32, alpha=alpha, stride=1, expansion=6, block_id=5) x = _inverted_res_block( x, filters=64, alpha=alpha, stride=2, expansion=6, block_id=6) x = _inverted_res_block( x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=7) x = _inverted_res_block( x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=8) x = _inverted_res_block( x, filters=64, alpha=alpha, stride=1, expansion=6, block_id=9) x = _inverted_res_block( x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=10) x = _inverted_res_block( x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=11) x = _inverted_res_block( x, filters=96, alpha=alpha, stride=1, expansion=6, block_id=12) x = _inverted_res_block( x, filters=160, alpha=alpha, stride=2, expansion=6, block_id=13) x = _inverted_res_block( x, filters=160, alpha=alpha, stride=1, expansion=6, block_id=14) x = _inverted_res_block( x, filters=160, alpha=alpha, stride=1, expansion=6, block_id=15) x = _inverted_res_block( x, filters=320, alpha=alpha, stride=1, expansion=6, block_id=16) # no alpha applied to last conv as stated in the paper: # if the width multiplier is greater than 1 we # increase the number of output channels if alpha > 1.0: last_block_filters = _make_divisible(1280 * alpha, 8) else: last_block_filters = 1280 x = layers.Conv2D( last_block_filters, kernel_size=1, use_bias=False, name='Conv_1')( x) x = layers.BatchNormalization( axis=channel_axis, epsilon=1e-3, momentum=0.999, name='Conv_1_bn')( x) x = layers.ReLU(6., name='out_relu')(x) if include_top: x = layers.GlobalAveragePooling2D()(x) imagenet_utils.validate_activation(classifier_activation, weights) x = layers.Dense(classes, activation=classifier_activation, name='predictions')(x) else: if pooling == 'avg': x = layers.GlobalAveragePooling2D()(x) elif pooling == 'max': x = layers.GlobalMaxPooling2D()(x) # Ensure that the model takes into account # any potential predecessors of `input_tensor`. if input_tensor is not None: inputs = layer_utils.get_source_inputs(input_tensor) else: inputs = img_input # Create model. model = training.Model(inputs, x, name='mobilenetv2_%0.2f_%s' % (alpha, rows)) # Load weights. if weights == 'imagenet': if include_top: model_name = ('mobilenet_v2_weights_tf_dim_ordering_tf_kernels_' + str(float(alpha)) + '_' + str(rows) + '.h5') weight_path = BASE_WEIGHT_PATH + model_name weights_path = data_utils.get_file( model_name, weight_path, cache_subdir='models') else: model_name = ('mobilenet_v2_weights_tf_dim_ordering_tf_kernels_' + str(float(alpha)) + '_' + str(rows) + '_no_top' + '.h5') weight_path = BASE_WEIGHT_PATH + model_name weights_path = data_utils.get_file( model_name, weight_path, cache_subdir='models') model.load_weights(weights_path) elif weights is not None: model.load_weights(weights) return model
def decode_predictions(preds, top=5)
-
Decodes the prediction of an ImageNet model.
Args
preds
- Numpy array encoding a batch of predictions.
top
- Integer, how many top-guesses to return. Defaults to 5.
Returns
A list of lists of top class prediction tuples
(class_name, class_description, score)
. One list of tuples per sample in batch input.Raises
ValueError
- In case of invalid shape of the
pred
array (must be 2D).
Expand source code
@keras_export('keras.applications.mobilenet_v2.decode_predictions') def decode_predictions(preds, top=5): return imagenet_utils.decode_predictions(preds, top=top)
def preprocess_input(x, data_format=None)
-
Preprocesses a tensor or Numpy array encoding a batch of images.
Usage example with
applications.MobileNet
:i = tf.keras.layers.Input([None, None, 3], dtype = tf.uint8) x = tf.cast(i, tf.float32) x = tf.keras.applications.mobilenet.preprocess_input(x) core = tf.keras.applications.MobileNet() x = core(x) model = tf.keras.Model(inputs=[i], outputs=[x]) image = tf.image.decode_png(tf.io.read_file('file.png')) result = model(image)
Args
x
- A floating point
numpy.array
or atf.Tensor
, 3D or 4D with 3 color channels, with values in the range [0, 255]. The preprocessed data are written over the input data if the data types are compatible. To avoid this behaviour,numpy.copy(x)
can be used. data_format
- Optional data format of the image tensor/array. Defaults to
None, in which case the global setting
tf.keras.backend.image_data_format()
is used (unless you changed it, it defaults to "channels_last").
Returns
Preprocessed
numpy.array
or atf.Tensor
with typefloat32
.The inputs pixel values are scaled between -1 and 1, sample-wise.
Raises
ValueError
- In case of unknown
data_format
argument.
Expand source code
@keras_export('keras.applications.mobilenet_v2.preprocess_input') def preprocess_input(x, data_format=None): return imagenet_utils.preprocess_input(x, data_format=data_format, mode='tf')