谷歌的开源深度学习工具 --py
简介
验证码主要用于防刷，传统的验证码识别算法一般需要把验证码分割为单个字符，然后逐个识别，如果字符之间相互重叠，传统的算法就然并卵了，本文采用cnn对验证码进行整体识别。通过本文的学习，大家可以学到几点：1.captcha库生成验证码；2.如何将验证码识别问题转化为分类问题；3.可以训练自己的验证码识别模型。
安装 captcha 库
sudo pip install captcha
生成验证码训练数据
所有的模型训练，数据是王道，本文采用 captcha 库生成验证码，captcha 可以生成语音和图片验证码，我们采用生成图片验证码功能，验证码是由数字、大写字母、小写字母组成（当然你也可以根据自己的需求调整，比如添加一些特殊字符），长度为 4，所以总共有 62^4 种组合验证码。
验证码生成器
采用 python 中生成器方式来生成我们的训练数据，这样的好处是，不需要提前生成大量的数据，训练过程中生成数据，并且可以无限生成数据。
|现在您可以在 /home/ubuntu 目录下创建源文件 generate_captcha.py，内容可参考：
#!/usr/bin/python
# -*- coding: utf-8 -*
from captcha.image import ImageCaptcha
from PIL import Image
import numpy as np
import random
import string
class generateCaptcha():
def __init__(self,
width = 160,#验证码图片的宽
height = 60,#验证码图片的高
char_num = 4,#验证码字符个数
characters = string.digits + string.ascii_uppercase + string.ascii_lowercase):#验证码组成，数字+大写字母+小写字母
self.width = width
self.height = height
self.char_num = char_num
self.characters = characters
self.classes = len(characters)
def gen_captcha(self,batch_size = 50):
X = np.zeros([batch_size,self.height,self.width,1])
img = np.zeros((self.height,self.width),dtype=np.uint8)
Y = np.zeros([batch_size,self.char_num,self.classes])
image = ImageCaptcha(width = self.width,height = self.height)
while True:
for i in range(batch_size):
captcha_str = ''.join(random.sample(self.characters,self.char_num))
img = image.generate_image(captcha_str).convert('L')
img = np.array(img.getdata())
X[i] = np.reshape(img,[self.height,self.width,1])/255.0
for j,ch in enumerate(captcha_str):
Y[i,j,self.characters.find(ch)] = 1
Y = np.reshape(Y,(batch_size,self.char_num*self.classes))
yield X,Y
def decode_captcha(self,y):
y = np.reshape(y,(len(y),self.char_num,self.classes))
return ''.join(self.characters[x] for x in np.argmax(y,axis = 2)[0,:])
def get_parameter(self):
return self.width,self.height,self.char_num,self.characters,self.classes
def gen_test_captcha(self):
image = ImageCaptcha(width = self.width,height = self.height)
captcha_str = ''.join(random.sample(self.characters,self.char_num))
img = image.generate_image(captcha_str)
img.save(captcha_str + '.jpg')
然后执行:
cd /home/ubuntu;
python
import generate_captcha
g = generate_captcha.generateCaptcha()
g.gen_test_captcha()
执行结果：
在 /home/ubuntu 目录下查看生成的验证码，jpg 格式的图片可以点击查看。
验证码识别模型
将验证码识别问题转化为分类问题，总共 62^4 种类型，采用 4 个 one-hot 编码分别表示 4 个字符取值。
cnn 验证码识别模型
3 层隐藏层、2 层全连接层，对每层都进行 dropout。input——>conv——>pool——>dropout——>conv——>pool——>dropout——>conv——>pool——>dropout——>fully connected layer——>dropout——>fully connected layer——>output
示例代码：
现在您可以在 /home/ubuntu 目录下创建源文件 captcha_model.py，内容可参考：
#!/usr/bin/python
# -*- coding: utf-8 -*
import tensorflow as tf
import math
class captchaModel():
def __init__(self,
width = 160,
height = 60,
char_num = 4,
classes = 62):
self.width = width
self.height = height
self.char_num = char_num
self.classes = classes
def conv2d(self,x, W):
return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding='SAME')
def max_pool_2x2(self,x):
return tf.nn.max_pool(x, ksize=[1, 2, 2, 1],
strides=[1, 2, 2, 1], padding='SAME')
def weight_variable(self,shape):
initial = tf.truncated_normal(shape, stddev=0.1)
return tf.Variable(initial)
def bias_variable(self,shape):
initial = tf.constant(0.1, shape=shape)
return tf.Variable(initial)
def create_model(self,x_images,keep_prob):
#first layer
w_conv1 = self.weight_variable([5, 5, 1, 32])
b_conv1 = self.bias_variable([32])
h_conv1 = tf.nn.relu(tf.nn.bias_add(self.conv2d(x_images, w_conv1), b_conv1))
h_pool1 = self.max_pool_2x2(h_conv1)
h_dropout1 = tf.nn.dropout(h_pool1,keep_prob)
conv_width = math.ceil(self.width/2)
conv_height = math.ceil(self.height/2)
#second layer
w_conv2 = self.weight_variable([5, 5, 32, 64])
b_conv2 = self.bias_variable([64])
h_conv2 = tf.nn.relu(tf.nn.bias_add(self.conv2d(h_dropout1, w_conv2), b_conv2))
h_pool2 = self.max_pool_2x2(h_conv2)
h_dropout2 = tf.nn.dropout(h_pool2,keep_prob)
conv_width = math.ceil(conv_width/2)
conv_height = math.ceil(conv_height/2)
#third layer
w_conv3 = self.weight_variable([5, 5, 64, 64])
b_conv3 = self.bias_variable([64])
h_conv3 = tf.nn.relu(tf.nn.bias_add(self.conv2d(h_dropout2, w_conv3), b_conv3))
h_pool3 = self.max_pool_2x2(h_conv3)
h_dropout3 = tf.nn.dropout(h_pool3,keep_prob)
conv_width = math.ceil(conv_width/2)
conv_height = math.ceil(conv_height/2)
#first fully layer
conv_width = int(conv_width)
conv_height = int(conv_height)
w_fc1 = self.weight_variable([64*conv_width*conv_height,1024])
b_fc1 = self.bias_variable([1024])
h_dropout3_flat = tf.reshape(h_dropout3,[-1,64*conv_width*conv_height])
h_fc1 = tf.nn.relu(tf.nn.bias_add(tf.matmul(h_dropout3_flat, w_fc1), b_fc1))
h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)
#second fully layer
w_fc2 = self.weight_variable([1024,self.char_num*self.classes])
b_fc2 = self.bias_variable([self.char_num*self.classes])
y_conv = tf.add(tf.matmul(h_fc1_drop, w_fc2), b_fc2)
return y_conv
训练 cnn 验证码识别模型
每批次采用 64 个训练样本，每 100 次循环采用 100 个测试样本检查识别准确度，当准确度大于 99% 时，训练结束，采用 GPU 需要 5-6 个小时左右，CPU 大概需要 20 个小时左右。
注：作为实验，你可以通过调整 train_captcha.py 文件中 if acc > 0.99: 代码行的准确度节省训练时间(比如将 0.99 为 0.01)；同时，我们已经通过长时间的训练得到了一个训练集，可以通过如下命令将训练集下载到本地。
wget http://tensorflow-1253902462.cosgz.myqcloud.com/captcha/capcha_model.zip
unzip capcha_model.zip
现在您可以在 /home/ubuntu 目录下创建源文件 train_captcha.py，内容可参考：
#!/usr/bin/python
import tensorflow as tf
import numpy as np
import string
import generate_captcha
import captcha_model
if __name__ == '__main__':
captcha = generate_captcha.generateCaptcha()
width,height,char_num,characters,classes = captcha.get_parameter()
x = tf.placeholder(tf.float32, [None, height,width,1])
y_ = tf.placeholder(tf.float32, [None, char_num*classes])
keep_prob = tf.placeholder(tf.float32)
model = captcha_model.captchaModel(width,height,char_num,classes)
y_conv = model.create_model(x,keep_prob)
cross_entropy = tf.reduce_mean(tf.nn.sigmoid_cross_entropy_with_logits(labels=y_,logits=y_conv))
train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy)
predict = tf.reshape(y_conv, [-1,char_num, classes])
real = tf.reshape(y_,[-1,char_num, classes])
correct_prediction = tf.equal(tf.argmax(predict,2), tf.argmax(real,2))
correct_prediction = tf.cast(correct_prediction, tf.float32)
accuracy = tf.reduce_mean(correct_prediction)
saver = tf.train.Saver()
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
step = 0
while True:
batch_x,batch_y = next(captcha.gen_captcha(64))
_,loss = sess.run([train_step,cross_entropy],feed_dict={x: batch_x, y_: batch_y, keep_prob: 0.75})
print ('step:%d,loss:%f' % (step,loss))
if step % 100 == 0:
batch_x_test,batch_y_test = next(captcha.gen_captcha(100))
acc = sess.run(accuracy, feed_dict={x: batch_x_test, y_: batch_y_test, keep_prob: 1.})
print ('###############################################step:%d,accuracy:%f' % (step,acc))
if acc > 0.99:
saver.save(sess,"capcha_model.ckpt")
break
step += 1
然后执行:
cd /home/ubuntu;
python train_captcha.py
执行结果：
step:75173,loss:0.010555
step:75174,loss:0.009410
step:75175,loss:0.009978
step:75176,loss:0.008089
step:75177,loss:0.009949
step:75178,loss:0.010126
step:75179,loss:0.009584
step:75180,loss:0.012272
step:75181,loss:0.010157
step:75182,loss:0.009529
step:75183,loss:0.007636
step:75184,loss:0.009058
step:75185,loss:0.010061
step:75186,loss:0.009941
step:75187,loss:0.009339
step:75188,loss:0.009685
step:75189,loss:0.009879
step:75190,loss:0.007799
step:75191,loss:0.010866
step:75192,loss:0.009838
step:75193,loss:0.010931
step:75194,loss:0.012859
step:75195,loss:0.008747
step:75196,loss:0.009147
step:75197,loss:0.009351
step:75198,loss:0.009746
step:75199,loss:0.010014
step:75200,loss:0.009024
###############################################step:75200,accuracy:0.992500
测试 cnn 验证码识别模型
示例代码：
现在您可以在 /home/ubuntu 目录下创建源文件 predict_captcha.py，内容可参考：
#!/usr/bin/python
from PIL import Image, ImageFilter
import tensorflow as tf
import numpy as np
import string
import sys
import generate_captcha
import captcha_model
if __name__ == '__main__':
captcha = generate_captcha.generateCaptcha()
width,height,char_num,characters,classes = captcha.get_parameter()
gray_image = Image.open(sys.argv[1]).convert('L')
img = np.array(gray_image.getdata())
test_x = np.reshape(img,[height,width,1])/255.0
x = tf.placeholder(tf.float32, [None, height,width,1])
keep_prob = tf.placeholder(tf.float32)
model = captcha_model.captchaModel(width,height,char_num,classes)
y_conv = model.create_model(x,keep_prob)
predict = tf.argmax(tf.reshape(y_conv, [-1,char_num, classes]),2)
init_op = tf.global_variables_initializer()
saver = tf.train.Saver()
gpu_options = tf.GPUOptions(per_process_gpu_memory_fraction=0.95)
with tf.Session(config=tf.ConfigProto(log_device_placement=False,gpu_options=gpu_options)) as sess:
sess.run(init_op)
saver.restore(sess, "capcha_model.ckpt")
pre_list = sess.run(predict,feed_dict={x: [test_x], keep_prob: 1})
for i in pre_list:
s = ''
for j in i:
s += characters[j]
print s
然后执行:
cd /home/ubuntu;
python predict_captcha.py Kz2J.jpg # 在你的机器上的验证码图片名称
执行结果：
Kz2J
注:因为实验时间的限制，你可能调整了准确度导致执行结果不符合预期，属于正常情况。
在训练时间足够长的情况下，你可以采用验证码生成器生成测试数据，cnn 训练出来的验证码识别模型还是很强大的，大小写的 z 都可以区分，甚至有时候人都无法区分，该模型也可以正确的识别。
更多 TensorFlow 的系列教程：
TensorFlow - 相关 API
TensorFlow - 线性回归
关于 TensorFlow 的更多资料可参考 TensorFlow 官网 。有墙，科学上网访问