实验内容
TensorFlow是由Google开发的用于数值计算的开源软件库,本实验采用 Captcha 库生成验证码,将验证码识别问题转化为分类问题,采用 CNN 网络模型进行训练,最终实现对验证码的破解。
免费在线实验地址:点击进入
实验资源:云服务器,没有云服务器的朋友推荐1折抢购:69元/年的阿里云服务器、或者88元/年的腾讯云服务器
软件环境Ubuntu 16.04.1 LTS 64 位
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。本教程将验证码识别问题转化为分类的问题,实现对验证码进行整体识别。 步骤简介本教程一共分为四个部分 - generate_captcha.py - 利用 Captcha 库生成验证码;
- captcha_model.py - CNN 模型;
- train_captcha.py - 训练 CNN 模型;
- predict_captcha.py - 识别验证码。
数据学习任务时间:时间未知 安装 captcha 库获取训练数据本教程使用的验证码由数字、大写字母、小写字母组成,每个验证码包含 4 个字符,总共有 62^4 种组合,所以一共有 62^4 种不同的验证码。 示例代码: 现在您可以在 /home/ubuntu 目录下创建源文件 generate_captcha.py,内容可参考: 示例代码:/home/ubuntu/generate_captcha.py- #-*- 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')
- X = np.zeros([1,self.height,self.width,1])
- Y = np.zeros([1,self.char_num,self.classes])
- img = img.convert('L')
- img = np.array(img.getdata())
- X[0] = np.reshape(img,[self.height,self.width,1])/255.0
- for j,ch in enumerate(captcha_str):
- Y[0,j,self.characters.find(ch)] = 1
- Y = np.reshape(Y,(1,self.char_num*self.classes))
- return X,Y
复制代码 理解训练数据- X:一个 mini-batch 的训练数据,其 shape 为 [ batch_size, height, width, 1 ],batch_size 表示每批次多少个训练数据,height 表示验证码图片的高,width 表示验证码图片的宽,1 表示图片的通道。
- Y:X 中每个训练数据属于哪一类验证码,其形状为 [ batch_size, class ] ,对验证码中每个字符进行 One-Hot 编码,所以 class 大小为 4*62。
执行: - 获取验证码和对应的分类
- cd /home/ubuntu;
- python
- from generate_captcha import generateCaptcha
- g = generateCaptcha()
- X,Y = g.gen_test_captcha()
复制代码
- 查看训练数据
可以在 /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。 模型学习任务时间:时间未知 CNN 模型总共 5 层网络,前 3 层为卷积层,第 4、5 层为全连接层。对 4 层隐藏层都进行 dropout。网络结构如下所示: 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: 示例代码:/home/ubuntu/captcha_model.py- # -*- 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
复制代码 训练 CNN 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 4-5 个小时左右,CPU 大概需要 20 个小时左右。 示例代码:现在您可以在 /home/ubuntu 目录下创建源文件 train_captcha.py,内容可参考: 示例代码:/home/ubuntu/train_captcha.py- #-*- coding:utf-8 -*-
- 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 = 1
- 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
复制代码 然后执行:- cd /home/ubuntu;
- python train_captcha.py
复制代码 执行结果:- 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
复制代码 使用训练好的模型: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),体验训练过程;我们已经通过长时间的训练得到了一个训练好的模型,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 -o capcha_model.zip
复制代码 识别验证码测试数据集:我们在腾讯云的 COS 上准备了 100 个验证码作为测试集,使用 wget 命令获取: - wget http://tensorflow-1253902462.cosgz.myqcloud.com/captcha/captcha.zip
- unzip -q captcha.zip
复制代码 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: 示例代码:/home/ubuntu/predict_captcha.py- #-*- coding:utf-8 -*-
- 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)
复制代码 然后执行:- cd /home/ubuntu;
- python predict_captcha.py captcha/0hWn.jpg
复制代码 执行结果:完成实验
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