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"""ResNet, ResNetV2, and ResNeXt models for Keras.
# Reference papers
- [Deep Residual Learning for Image Recognition]
(https://arxiv.org/abs/1512.03385) (CVPR 2016 Best Paper Award)
- [Identity Mappings in Deep Residual Networks]
(https://arxiv.org/abs/1603.05027) (ECCV 2016)
- [Aggregated Residual Transformations for Deep Neural Networks]
(https://arxiv.org/abs/1611.05431) (CVPR 2017)
# Reference implementations
- [TensorNets]
(https://github.com/taehoonlee/tensornets/blob/master/tensornets/resnets.py)
- [Caffe ResNet]
(https://github.com/KaimingHe/deep-residual-networks/tree/master/prototxt)
- [Torch ResNetV2]
(https://github.com/facebook/fb.resnet.torch/blob/master/models/preresnet.lua)
- [Torch ResNeXt]
(https://github.com/facebookresearch/ResNeXt/blob/master/models/resnext.lua)
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import os
from . import get_submodules_from_kwargs
from .imagenet_utils import _obtain_input_shape
backend = None
layers = None
models = None
keras_utils = None
BASE_WEIGHTS_PATH = (
'https://github.com/keras-team/keras-applications/'
'releases/download/resnet/')
WEIGHTS_HASHES = {
'resnet50': ('2cb95161c43110f7111970584f804107',
'4d473c1dd8becc155b73f8504c6f6626'),
'resnet101': ('f1aeb4b969a6efcfb50fad2f0c20cfc5',
'88cf7a10940856eca736dc7b7e228a21'),
'resnet152': ('100835be76be38e30d865e96f2aaae62',
'ee4c566cf9a93f14d82f913c2dc6dd0c'),
'resnet50v2': ('3ef43a0b657b3be2300d5770ece849e0',
'fac2f116257151a9d068a22e544a4917'),
'resnet101v2': ('6343647c601c52e1368623803854d971',
'c0ed64b8031c3730f411d2eb4eea35b5'),
'resnet152v2': ('a49b44d1979771252814e80f8ec446f9',
'ed17cf2e0169df9d443503ef94b23b33'),
'resnext50': ('67a5b30d522ed92f75a1f16eef299d1a',
'62527c363bdd9ec598bed41947b379fc'),
'resnext101': ('34fb605428fcc7aa4d62f44404c11509',
'0f678c91647380debd923963594981b3')
}
def block1(x, filters, kernel_size=3, stride=1,
conv_shortcut=True, name=None):
"""A residual block.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer.
kernel_size: default 3, kernel size of the bottleneck layer.
stride: default 1, stride of the first layer.
conv_shortcut: default True, use convolution shortcut if True,
otherwise identity shortcut.
name: string, block label.
# Returns
Output tensor for the residual block.
"""
bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1
if conv_shortcut is True:
shortcut = layers.Conv2D(4 * filters, 1, strides=stride,
name=name + '_0_conv')(x)
shortcut = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_0_bn')(shortcut)
else:
shortcut = x
x = layers.Conv2D(filters, 1, strides=stride, name=name + '_1_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_1_bn')(x)
x = layers.Activation('relu', name=name + '_1_relu')(x)
x = layers.Conv2D(filters, kernel_size, padding='SAME',
name=name + '_2_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_2_bn')(x)
x = layers.Activation('relu', name=name + '_2_relu')(x)
x = layers.Conv2D(4 * filters, 1, name=name + '_3_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_3_bn')(x)
x = layers.Add(name=name + '_add')([shortcut, x])
x = layers.Activation('relu', name=name + '_out')(x)
return x
def stack1(x, filters, blocks, stride1=2, name=None):
"""A set of stacked residual blocks.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer in a block.
blocks: integer, blocks in the stacked blocks.
stride1: default 2, stride of the first layer in the first block.
name: string, stack label.
# Returns
Output tensor for the stacked blocks.
"""
x = block1(x, filters, stride=stride1, name=name + '_block1')
for i in range(2, blocks + 1):
x = block1(x, filters, conv_shortcut=False, name=name + '_block' + str(i))
return x
def block2(x, filters, kernel_size=3, stride=1,
conv_shortcut=False, name=None):
"""A residual block.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer.
kernel_size: default 3, kernel size of the bottleneck layer.
stride: default 1, stride of the first layer.
conv_shortcut: default False, use convolution shortcut if True,
otherwise identity shortcut.
name: string, block label.
# Returns
Output tensor for the residual block.
"""
bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1
preact = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_preact_bn')(x)
preact = layers.Activation('relu', name=name + '_preact_relu')(preact)
if conv_shortcut is True:
shortcut = layers.Conv2D(4 * filters, 1, strides=stride,
name=name + '_0_conv')(preact)
else:
shortcut = layers.MaxPooling2D(1, strides=stride)(x) if stride > 1 else x
x = layers.Conv2D(filters, 1, strides=1, use_bias=False,
name=name + '_1_conv')(preact)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_1_bn')(x)
x = layers.Activation('relu', name=name + '_1_relu')(x)
x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name=name + '_2_pad')(x)
x = layers.Conv2D(filters, kernel_size, strides=stride,
use_bias=False, name=name + '_2_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_2_bn')(x)
x = layers.Activation('relu', name=name + '_2_relu')(x)
x = layers.Conv2D(4 * filters, 1, name=name + '_3_conv')(x)
x = layers.Add(name=name + '_out')([shortcut, x])
return x
def stack2(x, filters, blocks, stride1=2, name=None):
"""A set of stacked residual blocks.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer in a block.
blocks: integer, blocks in the stacked blocks.
stride1: default 2, stride of the first layer in the first block.
name: string, stack label.
# Returns
Output tensor for the stacked blocks.
"""
x = block2(x, filters, conv_shortcut=True, name=name + '_block1')
for i in range(2, blocks):
x = block2(x, filters, name=name + '_block' + str(i))
x = block2(x, filters, stride=stride1, name=name + '_block' + str(blocks))
return x
def block3(x, filters, kernel_size=3, stride=1, groups=32,
conv_shortcut=True, name=None):
"""A residual block.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer.
kernel_size: default 3, kernel size of the bottleneck layer.
stride: default 1, stride of the first layer.
groups: default 32, group size for grouped convolution.
conv_shortcut: default True, use convolution shortcut if True,
otherwise identity shortcut.
name: string, block label.
# Returns
Output tensor for the residual block.
"""
bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1
if conv_shortcut is True:
shortcut = layers.Conv2D((64 // groups) * filters, 1, strides=stride,
use_bias=False, name=name + '_0_conv')(x)
shortcut = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_0_bn')(shortcut)
else:
shortcut = x
x = layers.Conv2D(filters, 1, use_bias=False, name=name + '_1_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_1_bn')(x)
x = layers.Activation('relu', name=name + '_1_relu')(x)
c = filters // groups
x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name=name + '_2_pad')(x)
x = layers.DepthwiseConv2D(kernel_size, strides=stride, depth_multiplier=c,
use_bias=False, name=name + '_2_conv')(x)
x_shape = backend.int_shape(x)[1:-1]
x = layers.Reshape(x_shape + (groups, c, c))(x)
output_shape = x_shape + (groups, c) if backend.backend() == 'theano' else None
x = layers.Lambda(lambda x: sum([x[:, :, :, :, i] for i in range(c)]),
output_shape=output_shape, name=name + '_2_reduce')(x)
x = layers.Reshape(x_shape + (filters,))(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_2_bn')(x)
x = layers.Activation('relu', name=name + '_2_relu')(x)
x = layers.Conv2D((64 // groups) * filters, 1,
use_bias=False, name=name + '_3_conv')(x)
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name=name + '_3_bn')(x)
x = layers.Add(name=name + '_add')([shortcut, x])
x = layers.Activation('relu', name=name + '_out')(x)
return x
def stack3(x, filters, blocks, stride1=2, groups=32, name=None):
"""A set of stacked residual blocks.
# Arguments
x: input tensor.
filters: integer, filters of the bottleneck layer in a block.
blocks: integer, blocks in the stacked blocks.
stride1: default 2, stride of the first layer in the first block.
groups: default 32, group size for grouped convolution.
name: string, stack label.
# Returns
Output tensor for the stacked blocks.
"""
x = block3(x, filters, stride=stride1, groups=groups, name=name + '_block1')
for i in range(2, blocks + 1):
x = block3(x, filters, groups=groups, conv_shortcut=False,
name=name + '_block' + str(i))
return x
def ResNet(stack_fn,
preact,
use_bias,
model_name='resnet',
include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
"""Instantiates the ResNet, ResNetV2, and ResNeXt architecture.
Optionally loads weights pre-trained on ImageNet.
Note that the data format convention used by the model is
the one specified in your Keras config at `~/.keras/keras.json`.
# Arguments
stack_fn: a function that returns output tensor for the
stacked residual blocks.
preact: whether to use pre-activation or not
(True for ResNetV2, False for ResNet and ResNeXt).
use_bias: whether to use biases for convolutional layers or not
(True for ResNet and ResNetV2, False for ResNeXt).
model_name: string, model name.
include_top: whether to include the fully-connected
layer at the top of the network.
weights: 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.
input_shape: optional shape tuple, only to be specified
if `include_top` is False (otherwise the input shape
has to be `(224, 224, 3)` (with `channels_last` data format)
or `(3, 224, 224)` (with `channels_first` data format).
It should have exactly 3 inputs channels.
pooling: 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 layer.
- `avg` means that global average pooling
will be applied to the output of the
last convolutional layer, and thus
the output of the model will be a 2D tensor.
- `max` means that global max pooling will
be applied.
classes: optional number of classes to classify images
into, only to be specified if `include_top` is True, and
if no `weights` argument is specified.
# Returns
A Keras model instance.
# Raises
ValueError: in case of invalid argument for `weights`,
or invalid input shape.
"""
global backend, layers, models, keras_utils
backend, layers, models, keras_utils = get_submodules_from_kwargs(kwargs)
if not (weights in {'imagenet', None} or os.path.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
input_shape = _obtain_input_shape(input_shape,
default_size=224,
min_size=32,
data_format=backend.image_data_format(),
require_flatten=include_top,
weights=weights)
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
bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1
x = layers.ZeroPadding2D(padding=((3, 3), (3, 3)), name='conv1_pad')(img_input)
x = layers.Conv2D(64, 7, strides=2, use_bias=use_bias, name='conv1_conv')(x)
if preact is False:
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name='conv1_bn')(x)
x = layers.Activation('relu', name='conv1_relu')(x)
x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name='pool1_pad')(x)
x = layers.MaxPooling2D(3, strides=2, name='pool1_pool')(x)
x = stack_fn(x)
if preact is True:
x = layers.BatchNormalization(axis=bn_axis, epsilon=1.001e-5,
name='post_bn')(x)
x = layers.Activation('relu', name='post_relu')(x)
if include_top:
x = layers.GlobalAveragePooling2D(name='avg_pool')(x)
x = layers.Dense(classes, activation='softmax', name='probs')(x)
else:
if pooling == 'avg':
x = layers.GlobalAveragePooling2D(name='avg_pool')(x)
elif pooling == 'max':
x = layers.GlobalMaxPooling2D(name='max_pool')(x)
# Ensure that the model takes into account
# any potential predecessors of `input_tensor`.
if input_tensor is not None:
inputs = keras_utils.get_source_inputs(input_tensor)
else:
inputs = img_input
# Create model.
model = models.Model(inputs, x, name=model_name)
# Load weights.
if (weights == 'imagenet') and (model_name in WEIGHTS_HASHES):
if include_top:
file_name = model_name + '_weights_tf_dim_ordering_tf_kernels.h5'
file_hash = WEIGHTS_HASHES[model_name][0]
else:
file_name = model_name + '_weights_tf_dim_ordering_tf_kernels_notop.h5'
file_hash = WEIGHTS_HASHES[model_name][1]
weights_path = keras_utils.get_file(file_name,
BASE_WEIGHTS_PATH + file_name,
cache_subdir='models',
file_hash=file_hash)
model.load_weights(weights_path)
elif weights is not None:
model.load_weights(weights)
return model
def ResNet50(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack1(x, 64, 3, stride1=1, name='conv2')
x = stack1(x, 128, 4, name='conv3')
x = stack1(x, 256, 6, name='conv4')
x = stack1(x, 512, 3, name='conv5')
return x
return ResNet(stack_fn, False, True, 'resnet50',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNet101(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack1(x, 64, 3, stride1=1, name='conv2')
x = stack1(x, 128, 4, name='conv3')
x = stack1(x, 256, 23, name='conv4')
x = stack1(x, 512, 3, name='conv5')
return x
return ResNet(stack_fn, False, True, 'resnet101',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNet152(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack1(x, 64, 3, stride1=1, name='conv2')
x = stack1(x, 128, 8, name='conv3')
x = stack1(x, 256, 36, name='conv4')
x = stack1(x, 512, 3, name='conv5')
return x
return ResNet(stack_fn, False, True, 'resnet152',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNet50V2(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack2(x, 64, 3, name='conv2')
x = stack2(x, 128, 4, name='conv3')
x = stack2(x, 256, 6, name='conv4')
x = stack2(x, 512, 3, stride1=1, name='conv5')
return x
return ResNet(stack_fn, True, True, 'resnet50v2',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNet101V2(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack2(x, 64, 3, name='conv2')
x = stack2(x, 128, 4, name='conv3')
x = stack2(x, 256, 23, name='conv4')
x = stack2(x, 512, 3, stride1=1, name='conv5')
return x
return ResNet(stack_fn, True, True, 'resnet101v2',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNet152V2(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack2(x, 64, 3, name='conv2')
x = stack2(x, 128, 8, name='conv3')
x = stack2(x, 256, 36, name='conv4')
x = stack2(x, 512, 3, stride1=1, name='conv5')
return x
return ResNet(stack_fn, True, True, 'resnet152v2',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNeXt50(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack3(x, 128, 3, stride1=1, name='conv2')
x = stack3(x, 256, 4, name='conv3')
x = stack3(x, 512, 6, name='conv4')
x = stack3(x, 1024, 3, name='conv5')
return x
return ResNet(stack_fn, False, False, 'resnext50',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
def ResNeXt101(include_top=True,
weights='imagenet',
input_tensor=None,
input_shape=None,
pooling=None,
classes=1000,
**kwargs):
def stack_fn(x):
x = stack3(x, 128, 3, stride1=1, name='conv2')
x = stack3(x, 256, 4, name='conv3')
x = stack3(x, 512, 23, name='conv4')
x = stack3(x, 1024, 3, name='conv5')
return x
return ResNet(stack_fn, False, False, 'resnext101',
include_top, weights,
input_tensor, input_shape,
pooling, classes,
**kwargs)
setattr(ResNet50, '__doc__', ResNet.__doc__)
setattr(ResNet101, '__doc__', ResNet.__doc__)
setattr(ResNet152, '__doc__', ResNet.__doc__)
setattr(ResNet50V2, '__doc__', ResNet.__doc__)
setattr(ResNet101V2, '__doc__', ResNet.__doc__)
setattr(ResNet152V2, '__doc__', ResNet.__doc__)
setattr(ResNeXt50, '__doc__', ResNet.__doc__)
setattr(ResNeXt101, '__doc__', ResNet.__doc__)
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