はじめに

注：個人メモですので使用の際には自己責任で。
注：tensorflow2.3.0でのみ動作、正式実装ではない関数を使用しています。

tf.data.Datasetのdatasetパイプラインをflow_from_directory()のように手軽に作るクラスを定義する。
augmentaionも組み込んでおく（フリップ、回転、ズームのみ）。

以前の投稿も参照ください

python3

import tensorflow as tf
AUTOTUNE = tf.data.experimental.AUTOTUNE
import glob
import os
import numpy as np
import random

class creat_dataset_from_directory():
    def __init__(
    self,
    train_dir_path,
    valid_dir_path,
    img_height=150,
    img_width=150,
    batch_size=64,
    augmentation=False):
        self.train_dir = train_dir_path
        self.valid_dir = valid_dir_path
        self.height=img_height
        self.width=img_width
        self.batch_size=batch_size
        self.aug=augmentation
    
    def preprocess_image(self, image):
        image = tf.image.decode_jpeg(image, channels=3)#channelsは1だとGrayscale、３だとRGB
        image = tf.image.resize(image, [self.height, self.width])
        image /= 255.0  # normalize to [0,1] range
        return image

    def load_and_preprocess_image(self, path):
        image = tf.io.read_file(path)
        return self.preprocess_image(image)
    
    def return_dataset(self):
        label_names = [os.path.basename(i) for i in glob.glob(os.path.join(self.train_dir, '*')) if os.path.isdir(i)]
        label_names.sort()
        print('dataset has following {} classes : '.format(len(label_names)))
        label_to_index = dict((name, index) for index,name in enumerate(label_names))
        print(label_to_index)
        train_image_paths = glob.glob(os.path.join(self.train_dir, '*', '*jpg'))
        valid_image_paths = glob.glob(os.path.join(self.valid_dir, '*', '*jpg'))
        train_image_count = len(train_image_paths)
        valid_image_count = len(valid_image_paths)
        print('number of training image = ', train_image_count)
        print('number of validation image = ', valid_image_count)
        train_image_labels = [label_to_index[os.path.basename(os.path.dirname(path))]
                    for path in train_image_paths]
        valid_image_labels = [label_to_index[os.path.basename(os.path.dirname(path))]
                            for path in valid_image_paths]
        train_image_labels = tf.one_hot(train_image_labels, depth=len(label_names))
        valid_image_labels = tf.one_hot(valid_image_labels, depth=len(label_names))
        
        path_ds = tf.data.Dataset.from_tensor_slices(train_image_paths)
        label_ds = tf.data.Dataset.from_tensor_slices(train_image_labels)
        image_ds_train = path_ds.map(self.load_and_preprocess_image, num_parallel_calls=AUTOTUNE)
        label_ds_train = tf.data.Dataset.from_tensor_slices(tf.cast(train_image_labels, tf.int32))
        image_label_ds_train = tf.data.Dataset.zip((image_ds_train, label_ds_train))
        
        if not self.aug:        
            ds = image_label_ds_train
            ds = ds.repeat()
            ds = ds.shuffle(buffer_size=train_image_count) #shuffleの順序注意！
            ds = ds.batch(self.batch_size)
            ds = ds.prefetch(buffer_size=AUTOTUNE)
        else:
            data_augmentation = tf.keras.Sequential([
                                  tf.keras.layers.experimental.preprocessing.RandomFlip("horizontal_and_vertical"),
                                  tf.keras.layers.experimental.preprocessing.RandomRotation(0.2,fill_mode = 'reflect'),
                                  tf.keras.layers.experimental.preprocessing.RandomZoom(height_factor=0.2, fill_mode =  'reflect'),
                                    #tf.keras.layers.experimental.preprocessing.RandomCrop(140,140),
                                    #tf.keras.layers.experimental.preprocessing.RandomContrast(0.3),
                                    #tf.keras.layers.experimental.preprocessing.RandomTranslation(0.2,0.2),
                                ])
            ds = image_label_ds_train
            ds = ds.repeat()
            ds = ds.shuffle(buffer_size=train_image_count) #shuffleの順序注意！
            ds = ds.batch(self.batch_size)
            ds = ds.map(lambda x, y: (data_augmentation(x, training=True), y))

            ds = ds.prefetch(buffer_size=AUTOTUNE)
        
        path_ds_valid = tf.data.Dataset.from_tensor_slices(valid_image_paths)
        image_ds_valid = path_ds_valid.map(self.load_and_preprocess_image, num_parallel_calls=AUTOTUNE)
        label_ds_valid = tf.data.Dataset.from_tensor_slices(tf.cast(valid_image_labels, tf.int32))
        image_label_ds_valid = tf.data.Dataset.zip((image_ds_valid, label_ds_valid))
        ds_valid = image_label_ds_valid
        ds_valid = ds_valid.repeat()
        ds_valid = ds_valid.batch(self.batch_size)
        ds_valid = ds_valid.prefetch(buffer_size=AUTOTUNE)       
        
        #training、validationのdataset, trainingとvalidationの画像数が返されます。
        return ds, ds_valid, train_image_count, valid_image_count

使用方法

trainingとvalidationのフォルダに学習画像を分ける。
各フォルダにはラベルごとにフォルダを作って画像を入れる。
kerasのfrow_from_directoryと一緒

python3

h,w = 150,150
batch_size = 64
creat_ds = creat_dataset_from_directory(train_dir_path='./dataset',
                             valid_dir_path='./validation',
                             img_height=h,img_width=w,
                             batch_size=batch_size,
                             augmentation=True)
ds_train, ds_valid,train_image_count, valid_image_count = creat_ds.return_dataset()

出力結果

dataset has following 5 classes : 
{'daisy': 0, 'dandelion': 1, 'roses': 2, 'sunflowers': 3, 'tulips': 4}
number of training image =  3301
number of validation image =  369

モデルを作って、学習する

trainとvalidationのdatasetが返されるので、そのままfitする。（モデルは適当に作りました。）

python3

from tensorflow.keras.models import Sequential
from tensorflow.keras.layers import Dense, Conv2D, Flatten, Dropout, MaxPooling2D,BatchNormalization
from tensorflow.keras.preprocessing.image import ImageDataGenerator

epochs = 20
model = Sequential([
    Conv2D(16, 3, padding='same', activation='relu', input_shape=(h, w,3)),
    BatchNormalization(),
    MaxPooling2D(),
    Conv2D(32, 3, padding='same', activation='relu'),
    BatchNormalization(),
    MaxPooling2D(),
    Conv2D(64, 3, padding='same', activation='relu'),
    BatchNormalization(),
    MaxPooling2D(),
    Dropout(0.5),
    Flatten(),
    Dense(512, activation='relu'),
    Dense(5, activation='softmax')
])

model.compile(optimizer='adam',
              loss='categorical_crossentropy',
              metrics=['accuracy'])

history = model.fit(ds_train, 
        epochs=epochs, 
        steps_per_epoch=train_image_count//batch_size,
        validation_data=ds_valid,
        validation_steps=valid_image_count//batch_size, 
        validation_batch_size=batch_size,
        max_queue_size=120, workers=30, use_multiprocessing=True,
        )

出力結果

Epoch 1/20
 1/51 [..............................] - ETA: 0s - loss: 2.6099 - accuracy: 0.2969WARNING:tensorflow:Callbacks method `on_train_batch_end` is slow compared to the batch time (batch time: 0.0165s vs `on_train_batch_end` time: 0.0273s). Check your callbacks.
51/51 [==============================] - 3s 55ms/step - loss: 2.8166 - accuracy: 0.4920 - val_loss: 9.0111 - val_accuracy: 0.2937
Epoch 2/20
51/51 [==============================] - 2s 47ms/step - loss: 1.0819 - accuracy: 0.5882 - val_loss: 17.7906 - val_accuracy: 0.2875
Epoch 3/20
51/51 [==============================] - 2s 47ms/step - loss: 0.9926 - accuracy: 0.6091 - val_loss: 17.1720 - val_accuracy: 0.2906
Epoch 4/20
51/51 [==============================] - 2s 46ms/step - loss: 1.0255 - accuracy: 0.6032 - val_loss: 10.6826 - val_accuracy: 0.2875
Epoch 5/20
51/51 [==============================] - 2s 47ms/step - loss: 0.9339 - accuracy: 0.6376 - val_loss: 7.2258 - val_accuracy: 0.3063
Epoch 6/20
51/51 [==============================] - 2s 47ms/step - loss: 0.9263 - accuracy: 0.6458 - val_loss: 2.4138 - val_accuracy: 0.3625
Epoch 7/20
51/51 [==============================] - 2s 46ms/step - loss: 0.8773 - accuracy: 0.6575 - val_loss: 1.8898 - val_accuracy: 0.4313
Epoch 8/20
51/51 [==============================] - 2s 46ms/step - loss: 0.8190 - accuracy: 0.6866 - val_loss: 1.3397 - val_accuracy: 0.4969
Epoch 9/20
51/51 [==============================] - 2s 47ms/step - loss: 0.8381 - accuracy: 0.6673 - val_loss: 1.2199 - val_accuracy: 0.5219
Epoch 10/20
51/51 [==============================] - 2s 46ms/step - loss: 0.8357 - accuracy: 0.6682 - val_loss: 0.8355 - val_accuracy: 0.6938
Epoch 11/20
51/51 [==============================] - 2s 47ms/step - loss: 0.8006 - accuracy: 0.6933 - val_loss: 0.8150 - val_accuracy: 0.7156
Epoch 12/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7640 - accuracy: 0.6994 - val_loss: 0.7955 - val_accuracy: 0.6969
Epoch 13/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7794 - accuracy: 0.6958 - val_loss: 0.7804 - val_accuracy: 0.7375
Epoch 14/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7668 - accuracy: 0.7071 - val_loss: 0.7873 - val_accuracy: 0.7500
Epoch 15/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7615 - accuracy: 0.6952 - val_loss: 0.6884 - val_accuracy: 0.7688
Epoch 16/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7184 - accuracy: 0.7178 - val_loss: 0.6732 - val_accuracy: 0.7781
Epoch 17/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7346 - accuracy: 0.7111 - val_loss: 0.7682 - val_accuracy: 0.7406
Epoch 18/20
51/51 [==============================] - 2s 47ms/step - loss: 0.6868 - accuracy: 0.7289 - val_loss: 0.6970 - val_accuracy: 0.7688
Epoch 19/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7411 - accuracy: 0.7148 - val_loss: 0.8185 - val_accuracy: 0.7125
Epoch 20/20
51/51 [==============================] - 2s 47ms/step - loss: 0.7106 - accuracy: 0.7292 - val_loss: 0.7481 - val_accuracy: 0.7375

おわりに

kerasのfrow_from_directoryのような感じにdatasetを作成するクラスを作成しました。これで少し便利になりそうですかね。