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# coding=utf-8 |
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from typing import List, Optional, 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 tensorflow.python.keras.utils import conv_utils |
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from deepreg.model import layer, layer_util |
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from deepreg.model.backbone.interface import Backbone |
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from deepreg.model.layer import Extraction |
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from deepreg.registry import REGISTRY |
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@REGISTRY.register_backbone(name="unet") |
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class UNet(Backbone): |
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""" |
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Class that implements an adapted 3D UNet. |
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Reference: |
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- O. Ronneberger, P. Fischer, and T. Brox, |
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“U-net: Convolutional networks for biomedical image segmentation,”, |
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Lecture Notes in Computer Science, 2015, vol. 9351, pp. 234–241. |
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https://arxiv.org/abs/1505.04597 |
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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: Optional[int], |
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depth: 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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extract_levels: Tuple = (0,), |
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pooling: bool = True, |
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concat_skip: bool = False, |
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encode_kernel_sizes: Union[int, List[int]] = 3, |
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decode_kernel_sizes: Union[int, List[int]] = 3, |
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encode_num_channels: Optional[Tuple] = None, |
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decode_num_channels: Optional[Tuple] = None, |
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strides: int = 2, |
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padding: str = "same", |
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name: str = "Unet", |
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**kwargs, |
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): |
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""" |
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Initialise UNet. |
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:param image_size: (dim1, dim2, dim3), dims of input image. |
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:param num_channel_initial: number of initial channels |
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:param depth: input is at level 0, bottom is at level depth. |
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:param out_kernel_initializer: kernel initializer for the last layer |
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:param out_activation: activation at the last layer |
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:param out_channels: number of channels for the output |
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:param extract_levels: list, which levels from net to extract. |
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:param pooling: for down-sampling, use non-parameterized |
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pooling if true, otherwise use conv3d |
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:param concat_skip: when up-sampling, concatenate skipped |
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tensor if true, otherwise use addition |
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:param encode_kernel_sizes: kernel size for down-sampling |
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:param decode_kernel_sizes: kernel size for up-sampling |
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:param encode_num_channels: filters/channels for down-sampling, |
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by default it is doubled at each layer during down-sampling |
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:param decode_num_channels: filters/channels for up-sampling, |
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by default it is the same as encode_num_channels |
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:param strides: strides for down-sampling |
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:param padding: padding mode for all conv layers |
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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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out_channels=out_channels, |
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num_channel_initial=num_channel_initial, |
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out_kernel_initializer=out_kernel_initializer, |
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out_activation=out_activation, |
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name=name, |
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**kwargs, |
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) |
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# save parameters |
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assert max(extract_levels) <= depth |
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self._extract_levels = extract_levels |
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self._depth = depth |
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# save extra parameters |
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self._concat_skip = concat_skip |
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self._pooling = pooling |
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self._encode_kernel_sizes = encode_kernel_sizes |
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self._decode_kernel_sizes = decode_kernel_sizes |
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self._encode_num_channels = encode_num_channels |
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self._decode_num_channels = decode_num_channels |
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self._strides = strides |
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self._padding = padding |
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# init layers |
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# all lists start with d = 0 |
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self._encode_convs = None |
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self._encode_pools = None |
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self._bottom_block = None |
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self._decode_deconvs = None |
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self._decode_convs = None |
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self._output_block = None |
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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=depth, |
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extract_levels=extract_levels, |
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encode_kernel_sizes=encode_kernel_sizes, |
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decode_kernel_sizes=decode_kernel_sizes, |
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encode_num_channels=encode_num_channels, |
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decode_num_channels=decode_num_channels, |
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strides=strides, |
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padding=padding, |
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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_encode_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 |
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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, filters: int, 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 filters: number of channels for output, arg for conv3d |
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:param kernel_size: arg for pool3d or conv3d |
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:param padding: arg for pool3d or conv3d |
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:param strides: arg for pool3d or conv3d |
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:return: a block consists of one or multiple layers |
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""" |
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if self._pooling: |
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return tfkl.MaxPool3D( |
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pool_size=kernel_size, strides=strides, padding=padding |
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) |
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else: |
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return layer.Conv3dBlock( |
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filters=filters, |
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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_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 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_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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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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if self._concat_skip: |
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return tfkl.Concatenate() |
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else: |
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return tfkl.Add() |
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def build_decode_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 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_output_block( |
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self, |
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image_size: Tuple[int], |
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extract_levels: Tuple[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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def build_layers( |
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self, |
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image_size: tuple, |
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num_channel_initial: int, |
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depth: int, |
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extract_levels: Tuple[int], |
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encode_kernel_sizes: Union[int, List[int]], |
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decode_kernel_sizes: Union[int, List[int]], |
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encode_num_channels: Optional[Tuple], |
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322
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decode_num_channels: Optional[Tuple], |
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323
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strides: int, |
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324
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padding: str, |
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325
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out_kernel_initializer: str, |
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326
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out_activation: str, |
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327
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out_channels: int, |
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328
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): |
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329
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""" |
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330
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Build layers that will be used in call. |
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331
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332
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:param image_size: (dim1, dim2, dim3). |
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333
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:param num_channel_initial: number of initial channels. |
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334
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:param depth: network starts with d = 0, and the bottom has d = depth. |
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335
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:param extract_levels: from which depths the output will be built. |
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336
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:param encode_kernel_sizes: kernel size for down-sampling |
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337
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:param decode_kernel_sizes: kernel size for up-sampling |
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338
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:param encode_num_channels: filters/channels for down-sampling, |
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339
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by default it is doubled at each layer during down-sampling |
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340
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:param decode_num_channels: filters/channels for up-sampling, |
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341
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by default it is the same as encode_num_channels |
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342
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:param strides: strides for down-sampling |
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343
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:param padding: padding mode for all conv layers |
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344
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:param out_kernel_initializer: initializer to use for kernels. |
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345
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:param out_activation: activation to use at end layer. |
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346
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:param out_channels: number of channels for the extractions |
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347
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""" |
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348
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if encode_num_channels is None: |
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349
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assert num_channel_initial >= 1 |
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350
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encode_num_channels = tuple( |
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351
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num_channel_initial * (2 ** d) for d in range(depth + 1) |
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352
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) |
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353
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assert len(encode_num_channels) == depth + 1 |
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354
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if decode_num_channels is None: |
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355
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decode_num_channels = encode_num_channels |
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356
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|
assert len(decode_num_channels) == depth + 1 |
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357
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if not self._concat_skip: |
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358
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# in case of adding skip tensors, the channels should match |
|
359
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|
if decode_num_channels != encode_num_channels: |
|
360
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|
raise ValueError( |
|
361
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|
|
"For UNet, if the skipped tensor is added " |
|
362
|
|
|
"instead of being concatenated, " |
|
363
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|
|
"the encode_num_channels and decode_num_channels " |
|
364
|
|
|
"should be the same. " |
|
365
|
|
|
f"But got encode_num_channels = {encode_num_channels}," |
|
366
|
|
|
f"decode_num_channels = {decode_num_channels}." |
|
367
|
|
|
) |
|
368
|
|
|
tensor_shapes = self.build_encode_layers( |
|
369
|
|
|
image_size=image_size, |
|
370
|
|
|
num_channels=encode_num_channels, |
|
371
|
|
|
depth=depth, |
|
372
|
|
|
encode_kernel_sizes=encode_kernel_sizes, |
|
373
|
|
|
strides=strides, |
|
374
|
|
|
padding=padding, |
|
375
|
|
|
) |
|
376
|
|
|
self.build_decode_layers( |
|
377
|
|
|
tensor_shapes=tensor_shapes, |
|
378
|
|
|
image_size=image_size, |
|
379
|
|
|
num_channels=decode_num_channels, |
|
380
|
|
|
depth=depth, |
|
381
|
|
|
extract_levels=extract_levels, |
|
382
|
|
|
decode_kernel_sizes=decode_kernel_sizes, |
|
383
|
|
|
strides=strides, |
|
384
|
|
|
padding=padding, |
|
385
|
|
|
out_kernel_initializer=out_kernel_initializer, |
|
386
|
|
|
out_activation=out_activation, |
|
387
|
|
|
out_channels=out_channels, |
|
388
|
|
|
) |
|
389
|
|
|
|
|
390
|
|
|
def build_encode_layers( |
|
391
|
|
|
self, |
|
392
|
|
|
image_size: Tuple, |
|
393
|
|
|
num_channels: Tuple, |
|
394
|
|
|
depth: int, |
|
395
|
|
|
encode_kernel_sizes: Union[int, List[int]], |
|
396
|
|
|
strides: int, |
|
397
|
|
|
padding: str, |
|
398
|
|
|
) -> List[Tuple]: |
|
399
|
|
|
""" |
|
400
|
|
|
Build layers for encoding. |
|
401
|
|
|
|
|
402
|
|
|
:param image_size: (dim1, dim2, dim3). |
|
403
|
|
|
:param num_channels: number of channels for each layer, |
|
404
|
|
|
starting from the top layer. |
|
405
|
|
|
:param depth: network starts with d = 0, and the bottom has d = depth. |
|
406
|
|
|
:param encode_kernel_sizes: kernel size for down-sampling |
|
407
|
|
|
:param strides: strides for down-sampling |
|
408
|
|
|
:param padding: padding mode for all conv layers |
|
409
|
|
|
:return: list of tensor shapes starting from d = 0 |
|
410
|
|
|
""" |
|
411
|
|
|
if isinstance(encode_kernel_sizes, int): |
|
412
|
|
|
encode_kernel_sizes = [encode_kernel_sizes] * (depth + 1) |
|
413
|
|
|
assert len(encode_kernel_sizes) == depth + 1 |
|
414
|
|
|
|
|
415
|
|
|
# encoding / down-sampling |
|
416
|
|
|
self._encode_convs = [] |
|
417
|
|
|
self._encode_pools = [] |
|
418
|
|
|
tensor_shape = image_size |
|
419
|
|
|
tensor_shapes = [tensor_shape] |
|
420
|
|
|
for d in range(depth): |
|
421
|
|
|
encode_conv = self.build_encode_conv_block( |
|
422
|
|
|
filters=num_channels[d], |
|
423
|
|
|
kernel_size=encode_kernel_sizes[d], |
|
424
|
|
|
padding=padding, |
|
425
|
|
|
) |
|
426
|
|
|
encode_pool = self.build_down_sampling_block( |
|
427
|
|
|
filters=num_channels[d], |
|
428
|
|
|
kernel_size=strides, |
|
429
|
|
|
strides=strides, |
|
430
|
|
|
padding=padding, |
|
431
|
|
|
) |
|
432
|
|
|
tensor_shape = tuple( |
|
433
|
|
|
conv_utils.conv_output_length( |
|
434
|
|
|
input_length=x, |
|
435
|
|
|
filter_size=strides, |
|
436
|
|
|
padding=padding, |
|
437
|
|
|
stride=strides, |
|
438
|
|
|
dilation=1, |
|
439
|
|
|
) |
|
440
|
|
|
for x in tensor_shape |
|
441
|
|
|
) |
|
442
|
|
|
self._encode_convs.append(encode_conv) |
|
443
|
|
|
self._encode_pools.append(encode_pool) |
|
444
|
|
|
tensor_shapes.append(tensor_shape) |
|
445
|
|
|
|
|
446
|
|
|
# bottom layer |
|
447
|
|
|
self._bottom_block = self.build_bottom_block( |
|
448
|
|
|
filters=num_channels[depth], |
|
449
|
|
|
kernel_size=encode_kernel_sizes[depth], |
|
450
|
|
|
padding=padding, |
|
451
|
|
|
) |
|
452
|
|
|
return tensor_shapes |
|
453
|
|
|
|
|
454
|
|
|
def build_decode_layers( |
|
455
|
|
|
self, |
|
456
|
|
|
tensor_shapes: List[Tuple], |
|
457
|
|
|
image_size: Tuple, |
|
458
|
|
|
num_channels: Tuple, |
|
459
|
|
|
depth: int, |
|
460
|
|
|
extract_levels: Tuple[int], |
|
461
|
|
|
decode_kernel_sizes: Union[int, List[int]], |
|
462
|
|
|
strides: int, |
|
463
|
|
|
padding: str, |
|
464
|
|
|
out_kernel_initializer: str, |
|
465
|
|
|
out_activation: str, |
|
466
|
|
|
out_channels: int, |
|
467
|
|
|
): |
|
468
|
|
|
""" |
|
469
|
|
|
Build layers for decoding. |
|
470
|
|
|
|
|
471
|
|
|
:param tensor_shapes: shapes calculated in encoder |
|
472
|
|
|
:param image_size: (dim1, dim2, dim3). |
|
473
|
|
|
:param num_channels: number of channels for each layer, |
|
474
|
|
|
starting from the top layer. |
|
475
|
|
|
:param depth: network starts with d = 0, and the bottom has d = depth. |
|
476
|
|
|
:param extract_levels: from which depths the output will be built. |
|
477
|
|
|
:param decode_kernel_sizes: kernel size for up-sampling |
|
478
|
|
|
:param strides: strides for down-sampling |
|
479
|
|
|
:param padding: padding mode for all conv layers |
|
480
|
|
|
:param out_kernel_initializer: initializer to use for kernels. |
|
481
|
|
|
:param out_activation: activation to use at end layer. |
|
482
|
|
|
:param out_channels: number of channels for the extractions |
|
483
|
|
|
""" |
|
484
|
|
|
# init params |
|
485
|
|
|
min_extract_level = min(extract_levels) |
|
486
|
|
|
if isinstance(decode_kernel_sizes, int): |
|
487
|
|
|
decode_kernel_sizes = [decode_kernel_sizes] * depth |
|
488
|
|
|
assert len(decode_kernel_sizes) == depth |
|
489
|
|
|
|
|
490
|
|
|
# decoding / up-sampling |
|
491
|
|
|
self._decode_deconvs = [] |
|
492
|
|
|
self._decode_convs = [] |
|
493
|
|
|
for d in range(depth - 1, min_extract_level - 1, -1): |
|
494
|
|
|
kernel_size = decode_kernel_sizes[d] |
|
495
|
|
|
output_padding = layer_util.deconv_output_padding( |
|
496
|
|
|
input_shape=tensor_shapes[d + 1], |
|
497
|
|
|
output_shape=tensor_shapes[d], |
|
498
|
|
|
kernel_size=kernel_size, |
|
499
|
|
|
stride=strides, |
|
500
|
|
|
padding=padding, |
|
501
|
|
|
) |
|
502
|
|
|
decode_deconv = self.build_up_sampling_block( |
|
503
|
|
|
filters=num_channels[d], |
|
504
|
|
|
output_padding=output_padding, |
|
505
|
|
|
kernel_size=kernel_size, |
|
506
|
|
|
strides=strides, |
|
507
|
|
|
padding=padding, |
|
508
|
|
|
output_shape=tensor_shapes[d], |
|
509
|
|
|
) |
|
510
|
|
|
decode_conv = self.build_decode_conv_block( |
|
511
|
|
|
filters=num_channels[d], kernel_size=kernel_size, padding=padding |
|
512
|
|
|
) |
|
513
|
|
|
self._decode_deconvs = [decode_deconv] + self._decode_deconvs |
|
514
|
|
|
self._decode_convs = [decode_conv] + self._decode_convs |
|
515
|
|
|
if min_extract_level > 0: |
|
516
|
|
|
# add Nones to make lists have length depth - 1 |
|
517
|
|
|
self._decode_deconvs = [None] * min_extract_level + self._decode_deconvs |
|
518
|
|
|
self._decode_convs = [None] * min_extract_level + self._decode_convs |
|
519
|
|
|
|
|
520
|
|
|
# extraction |
|
521
|
|
|
self._output_block = self.build_output_block( |
|
522
|
|
|
image_size=image_size, |
|
523
|
|
|
extract_levels=extract_levels, |
|
524
|
|
|
out_channels=out_channels, |
|
525
|
|
|
out_kernel_initializer=out_kernel_initializer, |
|
526
|
|
|
out_activation=out_activation, |
|
527
|
|
|
) |
|
528
|
|
|
|
|
529
|
|
|
def call(self, inputs: tf.Tensor, training=None, mask=None) -> tf.Tensor: |
|
|
|
|
|
|
530
|
|
|
""" |
|
531
|
|
|
Build compute graph based on built layers. |
|
532
|
|
|
|
|
533
|
|
|
:param inputs: image batch, shape = (batch, f_dim1, f_dim2, f_dim3, ch) |
|
534
|
|
|
:param training: None or bool. |
|
535
|
|
|
:param mask: None or tf.Tensor. |
|
536
|
|
|
:return: shape = (batch, f_dim1, f_dim2, f_dim3, out_channels) |
|
537
|
|
|
""" |
|
538
|
|
|
|
|
539
|
|
|
# encoding / down-sampling |
|
540
|
|
|
skips = [] |
|
541
|
|
|
encoded = inputs |
|
542
|
|
|
for d in range(self._depth): |
|
543
|
|
|
skip = self._encode_convs[d](inputs=encoded, training=training) |
|
544
|
|
|
encoded = self._encode_pools[d](inputs=skip, training=training) |
|
545
|
|
|
skips.append(skip) |
|
546
|
|
|
|
|
547
|
|
|
# bottom |
|
548
|
|
|
decoded = self._bottom_block(inputs=encoded, training=training) |
|
549
|
|
|
|
|
550
|
|
|
# decoding / up-sampling |
|
551
|
|
|
outs = [decoded] |
|
552
|
|
|
for d in range(self._depth - 1, min(self._extract_levels) - 1, -1): |
|
553
|
|
|
decoded = self._decode_deconvs[d](inputs=decoded, training=training) |
|
554
|
|
|
decoded = self.build_skip_block()([decoded, skips[d]]) |
|
555
|
|
|
decoded = self._decode_convs[d](inputs=decoded, training=training) |
|
556
|
|
|
outs = [decoded] + outs |
|
557
|
|
|
|
|
558
|
|
|
# output |
|
559
|
|
|
output = self._output_block(outs) |
|
560
|
|
|
|
|
561
|
|
|
return output |
|
562
|
|
|
|
|
563
|
|
|
def get_config(self) -> dict: |
|
564
|
|
|
"""Return the config dictionary for recreating this class.""" |
|
565
|
|
|
config = super().get_config() |
|
566
|
|
|
config.update( |
|
567
|
|
|
depth=self._depth, |
|
568
|
|
|
extract_levels=self._extract_levels, |
|
569
|
|
|
pooling=self._pooling, |
|
570
|
|
|
concat_skip=self._concat_skip, |
|
571
|
|
|
encode_kernel_sizes=self._encode_kernel_sizes, |
|
572
|
|
|
decode_kernel_sizes=self._decode_kernel_sizes, |
|
573
|
|
|
encode_num_channels=self._encode_num_channels, |
|
574
|
|
|
decode_num_channels=self._decode_num_channels, |
|
575
|
|
|
strides=self._strides, |
|
576
|
|
|
padding=self._padding, |
|
577
|
|
|
) |
|
578
|
|
|
return config |
|
579
|
|
|
|