在電腦視覺中學習調整大小

import os

os.environ["KERAS_BACKEND"] = "tensorflow"
import keras
from keras import ops
from keras import layers
import tensorflow as tf

import tensorflow_datasets as tfds

tfds.disable_progress_bar()

import matplotlib.pyplot as plt
import numpy as np

INP_SIZE = (300, 300)
TARGET_SIZE = (150, 150)
INTERPOLATION = "bilinear"

AUTO = tf.data.AUTOTUNE
BATCH_SIZE = 64
EPOCHS = 5

train_ds, validation_ds = tfds.load(
    "cats_vs_dogs",
    # Reserve 10% for validation
    split=["train[:40%]", "train[40%:50%]"],
    as_supervised=True,
)


def preprocess_dataset(image, label):
    image = ops.image.resize(image, (INP_SIZE[0], INP_SIZE[1]))
    label = ops.one_hot(label, num_classes=2)
    return (image, label)


train_ds = (
    train_ds.shuffle(BATCH_SIZE * 100)
    .map(preprocess_dataset, num_parallel_calls=AUTO)
    .batch(BATCH_SIZE)
    .prefetch(AUTO)
)
validation_ds = (
    validation_ds.map(preprocess_dataset, num_parallel_calls=AUTO)
    .batch(BATCH_SIZE)
    .prefetch(AUTO)
)

def conv_block(x, filters, kernel_size, strides, activation=layers.LeakyReLU(0.2)):
    x = layers.Conv2D(filters, kernel_size, strides, padding="same", use_bias=False)(x)
    x = layers.BatchNormalization()(x)
    if activation:
        x = activation(x)
    return x


def res_block(x):
    inputs = x
    x = conv_block(x, 16, 3, 1)
    x = conv_block(x, 16, 3, 1, activation=None)
    return layers.Add()([inputs, x])

    # Note: user can change num_res_blocks to >1 also if needed


def get_learnable_resizer(filters=16, num_res_blocks=1, interpolation=INTERPOLATION):
    inputs = layers.Input(shape=[None, None, 3])

    # First, perform naive resizing.
    naive_resize = layers.Resizing(*TARGET_SIZE, interpolation=interpolation)(inputs)

    # First convolution block without batch normalization.
    x = layers.Conv2D(filters=filters, kernel_size=7, strides=1, padding="same")(inputs)
    x = layers.LeakyReLU(0.2)(x)

    # Second convolution block with batch normalization.
    x = layers.Conv2D(filters=filters, kernel_size=1, strides=1, padding="same")(x)
    x = layers.LeakyReLU(0.2)(x)
    x = layers.BatchNormalization()(x)

    # Intermediate resizing as a bottleneck.
    bottleneck = layers.Resizing(*TARGET_SIZE, interpolation=interpolation)(x)

    # Residual passes.
    # First res_block will get bottleneck output as input
    x = res_block(bottleneck)
    # Remaining res_blocks will get previous res_block output as input
    for _ in range(num_res_blocks - 1):
        x = res_block(x)

    # Projection.
    x = layers.Conv2D(
        filters=filters, kernel_size=3, strides=1, padding="same", use_bias=False
    )(x)
    x = layers.BatchNormalization()(x)

    # Skip connection.
    x = layers.Add()([bottleneck, x])

    # Final resized image.
    x = layers.Conv2D(filters=3, kernel_size=7, strides=1, padding="same")(x)
    final_resize = layers.Add()([naive_resize, x])

    return keras.Model(inputs, final_resize, name="learnable_resizer")


learnable_resizer = get_learnable_resizer()

sample_images, _ = next(iter(train_ds))


plt.figure(figsize=(16, 10))
for i, image in enumerate(sample_images[:6]):
    image = image / 255

    ax = plt.subplot(3, 4, 2 * i + 1)
    plt.title("Input Image")
    plt.imshow(image.numpy().squeeze())
    plt.axis("off")

    ax = plt.subplot(3, 4, 2 * i + 2)
    resized_image = learnable_resizer(image[None, ...])
    plt.title("Resized Image")
    plt.imshow(resized_image.numpy().squeeze())
    plt.axis("off")

def get_model():
    backbone = keras.applications.DenseNet121(
        weights=None,
        include_top=True,
        classes=2,
        input_shape=((TARGET_SIZE[0], TARGET_SIZE[1], 3)),
    )
    backbone.trainable = True

    inputs = layers.Input((INP_SIZE[0], INP_SIZE[1], 3))
    x = layers.Rescaling(scale=1.0 / 255)(inputs)
    x = learnable_resizer(x)
    outputs = backbone(x)

    return keras.Model(inputs, outputs)

model = get_model()
model.compile(
    loss=keras.losses.CategoricalCrossentropy(label_smoothing=0.1),
    optimizer="sgd",
    metrics=["accuracy"],
)
model.fit(train_ds, validation_data=validation_ds, epochs=EPOCHS)

plt.figure(figsize=(16, 10))
for i, image in enumerate(sample_images[:6]):
    image = image / 255

    ax = plt.subplot(3, 4, 2 * i + 1)
    plt.title("Input Image")
    plt.imshow(image.numpy().squeeze())
    plt.axis("off")

    ax = plt.subplot(3, 4, 2 * i + 2)
    resized_image = learnable_resizer(image[None, ...])
    plt.title("Resized Image")
    plt.imshow(resized_image.numpy().squeeze() / 10)
    plt.axis("off")