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# coding=utf-8 |
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from typing import List, Tuple, Union |
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import tensorflow as tf |
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import tensorflow.keras.layers as tfkl |
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from deepreg.model import layer |
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from deepreg.model.backbone.u_net import AbstractUNet |
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from deepreg.registry import REGISTRY |
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class AdditiveUpsampling(tfkl.Layer): |
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def __init__( |
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self, |
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filters: int, |
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output_padding: int, |
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kernel_size: int, |
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padding: str, |
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strides: int, |
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output_shape: tuple, |
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name: str = "AdditiveUpsampling", |
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): |
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""" |
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Addictive up-sampling layer. |
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:param filters: number of channels for output |
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:param output_padding: padding for output |
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:param kernel_size: arg for deconv3d |
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:param padding: arg for deconv3d |
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:param strides: arg for deconv3d |
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:param output_shape: shape of the output tensor |
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:param name: name of the layer. |
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""" |
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super().__init__(name=name) |
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self.deconv3d = layer.Deconv3dBlock( |
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filters=filters, |
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output_padding=output_padding, |
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kernel_size=kernel_size, |
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strides=strides, |
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padding=padding, |
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) |
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self.resize = layer.Resize3d(shape=output_shape) |
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def call(self, inputs, **kwargs): |
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deconved = self.deconv3d(inputs) |
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resized = self.resize(inputs) |
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resized = tf.add_n(tf.split(resized, num_or_size_splits=2, axis=4)) |
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return deconved + resized |
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class Extraction(tfkl.Layer): |
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def __init__( |
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self, |
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image_size: Tuple[int], |
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extract_levels: List[int], |
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out_channels: int, |
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out_kernel_initializer: str, |
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out_activation: str, |
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name: str = "Extraction", |
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): |
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""" |
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:param image_size: such as (dim1, dim2, dim3) |
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:param extract_levels: number of extraction levels. |
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:param out_channels: number of channels for the extractions |
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:param out_kernel_initializer: initializer to use for kernels. |
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:param out_activation: activation to use at end layer. |
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:param name: name of the layer |
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""" |
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super().__init__(name=name) |
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self.extract_levels = extract_levels |
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self.max_level = max(extract_levels) |
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self.layers = [ |
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tf.keras.Sequential( |
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[ |
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tfkl.Conv3D( |
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filters=out_channels, |
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kernel_size=3, |
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strides=1, |
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padding="same", |
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kernel_initializer=out_kernel_initializer, |
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activation=out_activation, |
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), |
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layer.Resize3d(shape=image_size), |
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] |
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) |
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for _ in extract_levels |
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] |
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def call(self, inputs: List[tf.Tensor], **kwargs) -> tf.Tensor: |
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""" |
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:param inputs: a list of tensors |
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:param kwargs: |
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:return: |
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""" |
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return tf.add_n( |
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[ |
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self.layers[idx](inputs=inputs[self.max_level - level]) |
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for idx, level in enumerate(self.extract_levels) |
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] |
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) / len(self.extract_levels) |
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@REGISTRY.register_backbone(name="local") |
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class LocalNet(AbstractUNet): |
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""" |
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Build LocalNet for image registration. |
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Reference: |
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- Hu, Yipeng, et al. |
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"Weakly-supervised convolutional neural networks |
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for multimodal image registration." |
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Medical image analysis 49 (2018): 1-13. |
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https://doi.org/10.1016/j.media.2018.07.002 |
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- Hu, Yipeng, et al. |
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"Label-driven weakly-supervised learning |
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for multimodal deformable image registration," |
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https://arxiv.org/abs/1711.01666 |
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""" |
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def __init__( |
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self, |
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image_size: tuple, |
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num_channel_initial: int, |
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extract_levels: List[int], |
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out_kernel_initializer: str, |
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out_activation: str, |
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out_channels: int, |
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use_additive_upsampling: bool = True, |
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name: str = "LocalNet", |
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**kwargs, |
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): |
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""" |
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Init. |
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Image is encoded gradually, i from level 0 to D, |
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then it is decoded gradually, j from level D to 0. |
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Some of the decoded levels are used for generating extractions. |
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So, extract_levels are between [0, D]. |
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:param image_size: such as (dim1, dim2, dim3) |
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:param num_channel_initial: number of initial channels. |
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:param extract_levels: from which depths the output will be built. |
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:param out_kernel_initializer: initializer to use for kernels. |
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:param out_activation: activation to use at end layer. |
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:param out_channels: number of channels for the extractions |
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:param use_additive_upsampling: whether use additive up-sampling. |
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:param name: name of the backbone. |
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:param kwargs: additional arguments. |
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""" |
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super().__init__( |
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image_size=image_size, |
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num_channel_initial=num_channel_initial, |
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depth=max(extract_levels), |
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extract_levels=extract_levels, |
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out_kernel_initializer=out_kernel_initializer, |
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out_activation=out_activation, |
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out_channels=out_channels, |
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name=name, |
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**kwargs, |
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) |
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# save extra parameters |
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self._use_additive_upsampling = use_additive_upsampling |
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# build layers |
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self.build_layers( |
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image_size=image_size, |
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num_channel_initial=num_channel_initial, |
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depth=self._depth, |
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extract_levels=self._extract_levels, |
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downsample_kernel_sizes=[7] + [3] * self._depth, |
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upsample_kernel_sizes=3, |
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strides=2, |
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padding="same", |
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out_kernel_initializer=out_kernel_initializer, |
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out_activation=out_activation, |
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out_channels=out_channels, |
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) |
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def build_conv_block( |
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self, filters: int, kernel_size: int, padding: str |
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) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a conv block for down-sampling or up-sampling. |
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This block do not change the tensor shape (width, height, depth), |
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it only changes the number of channels. |
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:param filters: number of channels for output |
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:param kernel_size: arg for conv3d |
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:param padding: arg for conv3d |
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:return: a block consists of one or multiple layers |
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""" |
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return tf.keras.Sequential( |
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[ |
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layer.Conv3dBlock( |
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filters=filters, |
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kernel_size=kernel_size, |
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padding=padding, |
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), |
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layer.ResidualConv3dBlock( |
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filters=filters, |
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kernel_size=kernel_size, |
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padding=padding, |
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), |
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] |
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) |
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def build_down_sampling_block( |
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self, kernel_size: int, padding: str, strides: int |
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) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a block for down-sampling. |
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This block changes the tensor shape (width, height, depth), |
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but it does not changes the number of channels. |
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:param kernel_size: arg for pool3d |
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:param padding: arg for pool3d |
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:param strides: arg for pool3d |
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:return: a block consists of one or multiple layers |
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""" |
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return tfkl.MaxPool3D(pool_size=kernel_size, strides=strides, padding=padding) |
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def build_bottom_block( |
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self, filters: int, kernel_size: int, padding: str |
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) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a block for bottom layer. |
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This block do not change the tensor shape (width, height, depth), |
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it only changes the number of channels. |
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:param filters: number of channels for output |
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:param kernel_size: arg for conv3d |
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:param padding: arg for conv3d |
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:return: a block consists of one or multiple layers |
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""" |
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return layer.Conv3dBlock( |
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filters=filters, kernel_size=kernel_size, padding=padding |
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) |
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def build_up_sampling_block( |
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self, |
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filters: int, |
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output_padding: int, |
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kernel_size: int, |
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padding: str, |
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strides: int, |
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output_shape: tuple, |
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) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a block for up-sampling. |
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This block changes the tensor shape (width, height, depth), |
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but it does not changes the number of channels. |
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:param filters: number of channels for output |
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:param output_padding: padding for output |
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:param kernel_size: arg for deconv3d |
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:param padding: arg for deconv3d |
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:param strides: arg for deconv3d |
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:param output_shape: shape of the output tensor |
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:return: a block consists of one or multiple layers |
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""" |
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if self._use_additive_upsampling: |
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return AdditiveUpsampling( |
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filters=filters, |
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output_padding=output_padding, |
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kernel_size=kernel_size, |
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strides=strides, |
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padding=padding, |
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output_shape=output_shape, |
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) |
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return layer.Deconv3dBlock( |
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filters=filters, |
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output_padding=output_padding, |
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kernel_size=kernel_size, |
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strides=strides, |
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padding=padding, |
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) |
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def build_skip_block(self) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a block for combining skipped tensor and up-sampled one. |
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This block do not change the tensor shape (width, height, depth), |
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it only changes the number of channels. |
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The input to this block is a list of tensors. |
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:return: a block consists of one or multiple layers |
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""" |
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return tfkl.Add() |
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def build_output_block( |
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self, |
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image_size: Tuple[int], |
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extract_levels: List[int], |
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out_channels: int, |
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out_kernel_initializer: str, |
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out_activation: str, |
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) -> Union[tf.keras.Model, tfkl.Layer]: |
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""" |
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Build a block for output. |
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The input to this block is a list of tensors. |
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:param image_size: such as (dim1, dim2, dim3) |
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:param extract_levels: number of extraction levels. |
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:param out_channels: number of channels for the extractions |
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:param out_kernel_initializer: initializer to use for kernels. |
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:param out_activation: activation to use at end layer. |
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:return: a block consists of one or multiple layers |
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""" |
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return Extraction( |
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image_size=image_size, |
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extract_levels=extract_levels, |
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out_channels=out_channels, |
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out_kernel_initializer=out_kernel_initializer, |
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out_activation=out_activation, |
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) |
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