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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, layer_util |
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from deepreg.model.backbone.interface import Backbone |
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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(Backbone): |
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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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out_channels: int, |
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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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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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Image is encoded gradually, i from level 0 to E, |
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then it is decoded gradually, j from level E to D. |
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Some of the decoded levels are used for generating extractions. |
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So, extract_levels are between [0, E] with E = max(extract_levels), |
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and D = min(extract_levels). |
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:param image_size: such as (dim1, dim2, dim3) |
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:param out_channels: number of channels for the extractions |
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:param num_channel_initial: number of initial channels. |
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:param extract_levels: number of extraction levels. |
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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 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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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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self._extract_levels = extract_levels |
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self._use_additive_upsampling = use_additive_upsampling |
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self._extract_max_level = max(self._extract_levels) # E |
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self._extract_min_level = min(self._extract_levels) # D |
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# init layer variables |
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num_channels = [ |
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num_channel_initial * (2 ** level) |
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for level in range(self._extract_max_level + 1) |
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] # level 0 to E |
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kernel_sizes = [ |
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7 if level == 0 else 3 for level in range(self._extract_max_level + 1) |
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] |
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self._downsample_convs = [] |
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self._downsample_pools = [] |
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tensor_shape = image_size |
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self._tensor_shapes = [tensor_shape] |
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for i in range(self._extract_max_level): |
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downsample_conv = self.build_conv_block( |
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filters=num_channels[i], kernel_size=kernel_sizes[i], padding="same" |
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) |
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downsample_pool = self.build_down_sampling_block( |
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kernel_size=2, strides=2, padding="same" |
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) |
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tensor_shape = tuple((x + 1) // 2 for x in tensor_shape) |
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self._downsample_convs.append(downsample_conv) |
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self._downsample_pools.append(downsample_pool) |
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self._tensor_shapes.append(tensor_shape) |
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self._bottom_block = self.build_bottom_block( |
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filters=num_channels[-1], kernel_size=3, padding="same" |
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) # level E |
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self._upsample_deconvs = [] |
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self._upsample_convs = [] |
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for level in range( |
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self._extract_max_level - 1, self._extract_min_level - 1, -1 |
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): # level D to E-1 |
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padding = layer_util.deconv_output_padding( |
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input_shape=self._tensor_shapes[level + 1], |
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output_shape=self._tensor_shapes[level], |
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kernel_size=kernel_sizes[level], |
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stride=2, |
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padding="same", |
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) |
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upsample_deconv = self.build_up_sampling_block( |
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filters=num_channels[level], |
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output_padding=padding, |
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kernel_size=3, |
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strides=2, |
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padding="same", |
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output_shape=self._tensor_shapes[level], |
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) |
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upsample_conv = self.build_conv_block( |
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filters=num_channels[level], kernel_size=3, padding="same" |
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) |
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self._upsample_deconvs.append(upsample_deconv) |
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self._upsample_convs.append(upsample_conv) |
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self._output = self.build_output_block( |
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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_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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|
|
319
|
|
|
if self._use_additive_upsampling: |
|
320
|
|
|
return AdditiveUpsampling( |
|
321
|
|
|
filters=filters, |
|
322
|
|
|
output_padding=output_padding, |
|
323
|
|
|
kernel_size=kernel_size, |
|
324
|
|
|
strides=strides, |
|
325
|
|
|
padding=padding, |
|
326
|
|
|
output_shape=output_shape, |
|
327
|
|
|
) |
|
328
|
|
|
|
|
329
|
|
|
return layer.Deconv3dBlock( |
|
330
|
|
|
filters=filters, |
|
331
|
|
|
output_padding=output_padding, |
|
332
|
|
|
kernel_size=kernel_size, |
|
333
|
|
|
strides=strides, |
|
334
|
|
|
padding=padding, |
|
335
|
|
|
) |
|
336
|
|
|
|
|
337
|
|
|
def build_skip_block(self) -> Union[tf.keras.Model, tfkl.Layer]: |
|
338
|
|
|
""" |
|
339
|
|
|
Build a block for combining skipped tensor and up-sampled one. |
|
340
|
|
|
|
|
341
|
|
|
This block do not change the tensor shape (width, height, depth), |
|
342
|
|
|
it only changes the number of channels. |
|
343
|
|
|
|
|
344
|
|
|
The input to this block is a list of tensors. |
|
345
|
|
|
|
|
346
|
|
|
:return: a block consists of one or multiple layers |
|
347
|
|
|
""" |
|
348
|
|
|
return tfkl.Add() |
|
349
|
|
|
|
|
350
|
|
|
def build_output_block( |
|
351
|
|
|
self, |
|
352
|
|
|
image_size: Tuple[int], |
|
353
|
|
|
extract_levels: List[int], |
|
354
|
|
|
out_channels: int, |
|
355
|
|
|
out_kernel_initializer: str, |
|
356
|
|
|
out_activation: str, |
|
357
|
|
|
) -> Union[tf.keras.Model, tfkl.Layer]: |
|
358
|
|
|
""" |
|
359
|
|
|
Build a block for output. |
|
360
|
|
|
|
|
361
|
|
|
The input to this block is a list of tensors. |
|
362
|
|
|
|
|
363
|
|
|
:param image_size: such as (dim1, dim2, dim3) |
|
364
|
|
|
:param extract_levels: number of extraction levels. |
|
365
|
|
|
:param out_channels: number of channels for the extractions |
|
366
|
|
|
:param out_kernel_initializer: initializer to use for kernels. |
|
367
|
|
|
:param out_activation: activation to use at end layer. |
|
368
|
|
|
:return: a block consists of one or multiple layers |
|
369
|
|
|
""" |
|
370
|
|
|
return Extraction( |
|
371
|
|
|
image_size=image_size, |
|
372
|
|
|
extract_levels=extract_levels, |
|
373
|
|
|
out_channels=out_channels, |
|
374
|
|
|
out_kernel_initializer=out_kernel_initializer, |
|
375
|
|
|
out_activation=out_activation, |
|
376
|
|
|
) |
|
377
|
|
|
|
|
378
|
|
|
def call(self, inputs: tf.Tensor, training=None, mask=None) -> tf.Tensor: |
|
|
|
|
|
|
379
|
|
|
""" |
|
380
|
|
|
Build LocalNet graph based on built layers. |
|
381
|
|
|
|
|
382
|
|
|
:param inputs: image batch, shape = (batch, f_dim1, f_dim2, f_dim3, ch) |
|
383
|
|
|
:param training: None or bool. |
|
384
|
|
|
:param mask: None or tf.Tensor. |
|
385
|
|
|
:return: shape = (batch, f_dim1, f_dim2, f_dim3, out_channels) |
|
386
|
|
|
""" |
|
387
|
|
|
|
|
388
|
|
|
# down sample from level 0 to E |
|
389
|
|
|
# outputs used for decoding, encoded[i] corresponds -> level i |
|
390
|
|
|
# stored only 0 to E-1 |
|
391
|
|
|
skips = [] |
|
392
|
|
|
down_sampled = inputs |
|
393
|
|
|
for level in range(self._extract_max_level): # level 0 to E - 1 |
|
394
|
|
|
skip = self._downsample_convs[level](inputs=down_sampled, training=training) |
|
395
|
|
|
down_sampled = self._downsample_pools[level](inputs=skip, training=training) |
|
396
|
|
|
skips.append(skip) |
|
397
|
|
|
up_sampled = self._bottom_block( |
|
398
|
|
|
inputs=down_sampled, training=training |
|
399
|
|
|
) # level E of encoding/decoding |
|
400
|
|
|
|
|
401
|
|
|
# up sample from level E to D |
|
402
|
|
|
outs = [up_sampled] # level E |
|
403
|
|
|
for idx, level in enumerate( |
|
404
|
|
|
range(self._extract_max_level - 1, self._extract_min_level - 1, -1) |
|
405
|
|
|
): # level E-1 to D |
|
406
|
|
|
up_sampled = self._upsample_deconvs[idx]( |
|
407
|
|
|
inputs=up_sampled, training=training |
|
408
|
|
|
) |
|
409
|
|
|
up_sampled = self.build_skip_block()([up_sampled, skips[level]]) |
|
410
|
|
|
up_sampled = self._upsample_convs[idx](inputs=up_sampled, training=training) |
|
411
|
|
|
outs.append(up_sampled) |
|
412
|
|
|
|
|
413
|
|
|
# output |
|
414
|
|
|
output = self._output(outs) |
|
415
|
|
|
|
|
416
|
|
|
return output |
|
417
|
|
|
|