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NSFW 指的是 不合适工作场合（”Not Safe (or Suitable) For Work;”）。在本文中，将介绍如何创立一个检测 NSFW 图像的图像分类模型。
数据集
因为数据集的性质，咱们无奈从一些数据集的网站 (如 Kaggle 等) 取得所有图像。
然而咱们找到了一个专门抓取这种类型图片的 github 库，所以咱们能够间接应用。clone 我的项目后能够运行上面的代码来创立文件夹，并将每个图像下载到其特定的文件夹中。
folders = ['drawings','hentai','neutral','porn','sexy']
urls = ['urls_drawings.txt','urls_hentai.txt','urls_neutral.txt','urls_porn.txt','urls_sexy.txt']
names = ['d','h','n','p','s']
for i,j,k in zip(folders,urls,names):
try:
#Specify the path of the folder that has to be made
folder_path = os.path.join('your directory',i)
os.mkdir(folder_path)
except:
pass
#setup the path of url text file
url_path = os.path.join('Datasets_Urls',j)
my_file = open(url_path, "r")
data = my_file.read()
#create a list with all urls
data_into_list = data.split("\n")
my_file.close()
icount = 0
for ii in data_into_list:
try:
#create a unique image names for each images
image_name = 'image'+str(icount)+str(k)+'.png'
image_path = os.path.join(folder_path,image_name)
#download it using the library
urllib.request.urlretrieve(ii, image_path)
icount+=1
except Exception as e:
pass
#this below code is done to make the count of the image same for all the data
#you can use a big number if you are building a more complex model or if you have a good system
if icount == 2000:
break这里的 folder 变量示意类的名称，urls 变量用于获取 URL 文本文件(能够依据文本文件名更改它)，name 变量用于为每个图像创立惟一的名称。
下面代码将为每个类下载 2000 张图像，能够编辑最初一个“if”条件来更改下载图像的个数。
数据筹备
咱们下载的文件夹可能蕴含其余类型的文件，所以首先必须删除不须要的类型的文件。
image_exts = ['jpeg','.jpg','bmp','png']
path_list = ['drawings','hentai','neutral','porn','sexy']
cwd = os.getcwd()
def remove_other_images(path_list):
for ii in path_list:
data_dir = os.path.join(cwd,'DataSet',ii)
for image in os.listdir(os.path.join(data_dir)):
image_path = os.path.join(data_dir,image_class,image)
try:
img = cv2.imread(image_path)
tip = imghdr.what(image_path)
if tip not in image_exts:
print('Image not in ext list {}'.format(image_path))
os.remove(image_path)
except Exception as e:
print("Issue with image {}".format(image_path))
remove_other_images(path_list)下面的代码删除了扩展名不是指定格局的图像。
另外图像可能蕴含许多反复的图像，所以咱们必须从每个文件夹中删除反复的图像。
cwd = os.getcwd()
path_list = ['drawings','hentai','neutral','porn','sexy']
def remove_dup_images(path_list):
for ii in path_list:
os.chdir(os.path.join(cwd,'DataSet',ii))
filelist = os.listdir()
duplicates = []
hash_keys = dict()
for index, filename in enumerate(filelist):
if os.path.isfile(filename):
with open(filename,'rb') as f:
filehash = hashlib.md5(f.read()).hexdigest()
if filehash not in hash_keys:
hash_keys[filehash] = index
else:
duplicates.append((index,hash_keys[filehash]))
for index in duplicates:
os.remove(filelist[index[0]])
print('{} duplicates removed from {}'.format(len(duplicates),ii))
remove_dup_images(path_list)这里咱们应用 hashlib.md5 编码来查找每个类中的反复图像。
Md5 为每个图像创立一个惟一的哈希值，如果哈希值反复(反复图像)，那么咱们将反复图片增加到一个列表中，稍后进行删除。
因为应用 TensorFlow 框架所以须要判断是否被 TensorFlow 反对，所以咱们这里加一个判断：
import tensorflow as tf
os.chdir('{data-set} directory')
cwd = os.getcwd()
for ii in path_list:
os.chdir(os.path.join(cwd,ii))
filelist = os.listdir()
for image_file in filelist:
with open(image_file, 'rb') as f:
image_data = f.read()
# Check the file format
_, ext = os.path.splitext(image_file)
if ext.lower() not in ['.jpg', '.jpeg', '.png', '.gif', '.bmp']:
print('Unsupported image format:', ext)
os.remove(os.path.join(cwd,ii,image_file))
else:
# Decode the image
try:
image = tf.image.decode_image(image_data)
except:
print(image_file)
print("unspported")
os.remove(os.path.join(cwd,ii,image_file))以上就是数据筹备的所有工作，在清理完数据后，咱们能够拆分数据。比方宰割创立一个训练、验证和测试文件夹，并手动增加文件夹中的图像，咱们将 80% 用于训练，10% 用于验证，10% 用于测试。
模型
首先导入 tensorflow
import tensorflow as tf
import os
import numpy as np
import matplotlib.pyplot as plt
from sklearn.utils import shuffle
import hashlib
from imageio import imread
import numpy as np
from tensorflow.keras.preprocessing.image import ImageDataGenerator
from tensorflow.keras.applications.vgg16 import VGG16
from tensorflow.keras.applications.vgg16 import preprocess_input
from tensorflow.keras.layers import Flatten,Dense,Input
from tensorflow.keras.models import Model,Sequential
from keras import optimizers对于图像，默认大小设置为 224,224。
IMAGE_SIZE = [224,224]能够应用 ImageDataGenerator 库，进行数据加强。数据加强也叫数据裁减，是为了减少数据集的大小。ImageDataGenerator 依据给定的参数创立新图像，并将其用于训练(留神: 当应用 ImageDataGenerator 时，原始数据将不用于训练)。
train_datagen = ImageDataGenerator(
rescale=1./255,
preprocessing_function=preprocess_input,
rotation_range=40,
width_shift_range=0.2,
height_shift_range=0.2,
shear_range=0.2,
zoom_range=0.2,
horizontal_flip=True,
fill_mode='nearest')对于测试集也是这样：
test_datagen = ImageDataGenerator(rescale=1./255)为了演示，咱们间接应用 VGG 模型
vgg = VGG16(input_shape=IMAGE_SIZE+[3],weights='imagenet',include_top=False而后解冻后面的层：
for layer in vgg.layers:
layer.trainable = False最初咱们退出本人的分类头：
x = Flatten()(vgg.output)
prediction = Dense(5,activation='softmax')(x)
model = Model(inputs=vgg.input, outputs=prediction)
model.summary()模型是这样的：
训练
看看咱们训练集：
train_set = train_datagen.flow_from_directory('DataSet/train',
target_size=(224,224),
batch_size=32,
class_mode='sparse')验证集
val_set = train_datagen.flow_from_directory('DataSet/validation',
target_size=(224,224),
batch_size=32,
class_mode='sparse')应用 ’ sparse_categorical_crossentropy ‘ 损失，这样能够将标签编码为整数而不是独热编码。
from tensorflow.keras.metrics import MeanSquaredError
from tensorflow.keras.metrics import CategoricalAccuracy
adam = optimizers.Adam()
model.compile(loss='sparse_categorical_crossentropy',
optimizer=adam,
metrics=['accuracy',MeanSquaredError(name='val_loss'),CategoricalAccuracy(name='val_accuracy')])而后就能够训练了：
from datetime import datetime
from keras.callbacks import ModelCheckpoint
log_dir = 'vg_log'
tensorboard_callback = tf.keras.callbacks.TensorBoard(log_dir = log_dir)
start = datetime.now()
history = model.fit_generator(train_set,
validation_data=val_set,
epochs=100,
steps_per_epoch=len(train_set)// batch_size,
validation_steps=len(val_set)//batch_size,
callbacks=[tensorboard_callback],
verbose=1)
duration = datetime.now() - start
print("Time taken for training is",duration)模型训练了 100 次。失去了 80% 的验证准确率。f1 得分为 93%
预测
上面的函数将获取一个图像列表并依据该列表进行预测。
import numpy as np
import matplotlib.image as mpimg
import matplotlib.pyplot as plt
from scipy.ndimage import gaussian_filter
def print_classes(images,model):
classes = ['Drawing','Hentai','Neutral','Porn','Sexual']
fig, ax = plt.subplots(ncols=len(images), figsize=(20,20))
for idx,img in enumerate(images):
img = mpimg.imread(img)
resize = tf.image.resize(img,(224,224))
result = model.predict(np.expand_dims(resize/255,0))
result = np.argmax(result)
if classes[result] == 'Porn':
img = gaussian_filter(img, sigma=6)
elif classes[result] == 'Sexual':
img = gaussian_filter(img, sigma=6)
elif classes[result] == 'Hentai':
img = gaussian_filter(img, sigma=6)
ax[idx].imshow(img)
ax[idx].title.set_text(classes[result])
li = ['test1.jpeg','test2.jpeg','test3.jpeg','test4.jpeg','test5.jpeg']
print_classes(li,model)看后果还是能够的。
最初，本文的源代码：
https://avoid.overfit.cn/post/8f681841d02e4a8db7bcf77926e123f1
作者：Nikhil Thalappalli
正文完
