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# Pass the list of images and the list of corresponding captions |
train_dataset = make_dataset(list(train_data.keys()), list(train_data.values())) |
valid_dataset = make_dataset(list(valid_data.keys()), list(valid_data.values())) |
Building the model |
Our image captioning architecture consists of three models: |
A CNN: used to extract the image features |
A TransformerEncoder: The extracted image features are then passed to a Transformer based encoder that generates a new representation of the inputs |
A TransformerDecoder: This model takes the encoder output and the text data (sequences) as inputs and tries to learn to generate the caption. |
def get_cnn_model(): |
base_model = efficientnet.EfficientNetB0( |
input_shape=(*IMAGE_SIZE, 3), include_top=False, weights=\"imagenet\", |
) |
# We freeze our feature extractor |
base_model.trainable = False |
base_model_out = base_model.output |
base_model_out = layers.Reshape((-1, base_model_out.shape[-1]))(base_model_out) |
cnn_model = keras.models.Model(base_model.input, base_model_out) |
return cnn_model |
class TransformerEncoderBlock(layers.Layer): |
def __init__(self, embed_dim, dense_dim, num_heads, **kwargs): |
super().__init__(**kwargs) |
self.embed_dim = embed_dim |
self.dense_dim = dense_dim |
self.num_heads = num_heads |
self.attention_1 = layers.MultiHeadAttention( |
num_heads=num_heads, key_dim=embed_dim, dropout=0.0 |
) |
self.layernorm_1 = layers.LayerNormalization() |
self.layernorm_2 = layers.LayerNormalization() |
self.dense_1 = layers.Dense(embed_dim, activation=\"relu\") |
def call(self, inputs, training, mask=None): |
inputs = self.layernorm_1(inputs) |
inputs = self.dense_1(inputs) |
attention_output_1 = self.attention_1( |
query=inputs, |
value=inputs, |
key=inputs, |
attention_mask=None, |
training=training, |
) |
out_1 = self.layernorm_2(inputs + attention_output_1) |
return out_1 |
class PositionalEmbedding(layers.Layer): |
def __init__(self, sequence_length, vocab_size, embed_dim, **kwargs): |
super().__init__(**kwargs) |
self.token_embeddings = layers.Embedding( |
input_dim=vocab_size, output_dim=embed_dim |
) |
self.position_embeddings = layers.Embedding( |
input_dim=sequence_length, output_dim=embed_dim |
) |
self.sequence_length = sequence_length |
self.vocab_size = vocab_size |
self.embed_dim = embed_dim |
self.embed_scale = tf.math.sqrt(tf.cast(embed_dim, tf.float32)) |
def call(self, inputs): |
length = tf.shape(inputs)[-1] |
positions = tf.range(start=0, limit=length, delta=1) |
embedded_tokens = self.token_embeddings(inputs) |
embedded_tokens = embedded_tokens * self.embed_scale |
embedded_positions = self.position_embeddings(positions) |
return embedded_tokens + embedded_positions |
def compute_mask(self, inputs, mask=None): |
return tf.math.not_equal(inputs, 0) |
class TransformerDecoderBlock(layers.Layer): |
def __init__(self, embed_dim, ff_dim, num_heads, **kwargs): |
super().__init__(**kwargs) |
self.embed_dim = embed_dim |
self.ff_dim = ff_dim |
self.num_heads = num_heads |
self.attention_1 = layers.MultiHeadAttention( |
num_heads=num_heads, key_dim=embed_dim, dropout=0.1 |
) |
self.attention_2 = layers.MultiHeadAttention( |
num_heads=num_heads, key_dim=embed_dim, dropout=0.1 |
) |
self.ffn_layer_1 = layers.Dense(ff_dim, activation=\"relu\") |
self.ffn_layer_2 = layers.Dense(embed_dim) |
self.layernorm_1 = layers.LayerNormalization() |
self.layernorm_2 = layers.LayerNormalization() |
self.layernorm_3 = layers.LayerNormalization() |
self.embedding = PositionalEmbedding( |
embed_dim=EMBED_DIM, sequence_length=SEQ_LENGTH, vocab_size=VOCAB_SIZE |
) |
self.out = layers.Dense(VOCAB_SIZE, activation=\"softmax\") |
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