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import tensorflow as tf
from tensorflow.keras import layers
class PatchExtract(layers.Layer):
def __init__(self, patch_size, **kwargs):
super().__init__(**kwargs)
self.patch_size_x = patch_size[0]
self.patch_size_y = patch_size[0]
def call(self, images):
batch_size = tf.shape(images)[0]
patches = tf.image.extract_patches(
images=images,
sizes=(1, self.patch_size_x, self.patch_size_y, 1),
strides=(1, self.patch_size_x, self.patch_size_y, 1),
rates=(1, 1, 1, 1),
padding="VALID",
)
patch_dim = patches.shape[-1]
patch_num = patches.shape[1]
return tf.reshape(patches, (batch_size, patch_num * patch_num, patch_dim))
def get_config(self):
config = super().get_config()
config.update(
{
"patch_size_y": self.patch_size_y,
"patch_size_x": self.patch_size_x,
}
)
return config
class PatchEmbedding(layers.Layer):
def __init__(self, num_patch, embed_dim, **kwargs):
super().__init__(**kwargs)
self.num_patch = num_patch
self.proj = layers.Dense(embed_dim)
self.pos_embed = layers.Embedding(input_dim=num_patch, output_dim=embed_dim)
def call(self, patch):
pos = tf.range(start=0, limit=self.num_patch, delta=1)
return self.proj(patch) + self.pos_embed(pos)
def get_config(self):
config = super().get_config()
config.update(
{
"num_patch": self.num_patch,
}
)
return config
class PatchMerging(layers.Layer):
def __init__(self, num_patch, embed_dim):
super().__init__()
self.num_patch = num_patch
self.embed_dim = embed_dim
self.linear_trans = layers.Dense(2 * embed_dim, use_bias=False)
def call(self, x):
height, width = self.num_patch
_, _, C = x.get_shape().as_list()
x = tf.reshape(x, shape=(-1, height, width, C))
feat_maps = x
x0 = x[:, 0::2, 0::2, :]
x1 = x[:, 1::2, 0::2, :]
x2 = x[:, 0::2, 1::2, :]
x3 = x[:, 1::2, 1::2, :]
x = tf.concat((x0, x1, x2, x3), axis=-1)
x = tf.reshape(x, shape=(-1, (height // 2) * (width // 2), 4 * C))
return self.linear_trans(x), feat_maps
def get_config(self):
config = super().get_config()
config.update({"num_patch": self.num_patch, "embed_dim": self.embed_dim})
return config
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