CNN识别验证码1

之前学习python的时候，想尝试用requests实现自动登陆，但是现在网站登陆都会有验证码保护，主要是为了防止暴力破解，任意用户注册。最近接触深度学习，cnn能够进行图像识别，能够进行验证码识别。

主要步骤：

1、采样制作样本文件

2、根据样本文件类型创建识别模型

3、对样本文件分为训练样本和测试样本来训练识别模型

4、保存识别模型和验证

第一步生成验证码，保存文件为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)  #10+26+26=62

     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

返回参数的含义：

• 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。

调用这个类的时候会生成这样的验证码图片：

第二步创建识别模型

这里用到了 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

主要代码（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')  #步长是1，卷积的时候图片大小没有缩小。最大池化的时候图片减为一半。

     def max_pool_2x2(self,x):
         return tf.nn.max_pool(x, ksize=[1, 2, 2, 1],                      #用2*2的过滤器
                               strides=[1, 2, 2, 1], padding='SAME')       #最大池化步长是2

     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])   #通过过滤器计算权重值5*5*32
         b_conv1 = self.bias_variable([32])               #32是[5,5,1,32]中的32的输出。a[1]=Relu(w[1]a[0]+b[1]),因为w[1]a[0]是32，矩阵相加。
         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])  #64*20*8
         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

第三步，有了样本和模型可以训练识别模型

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。

主要代码（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]) #占位符
     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))#將tensor取平均，第二個參數代表沿著那一維取平均
     train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy)  #优化器

     predict = tf.reshape(y_conv, [-1,char_num, classes])    #y_conv通过模型获得的
     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:                      #准确率
                     saver.save(sess,"capcha_model.ckpt")  #保存模型文件
                     break
             step += 1

进行训练，查看训练过程(这里为了快速得到模型，我们将acc改的很小。训练模型也不准确)：

当训练好后会生成以下模型文件，其中checkpoint保存模型路劲和一些模型信息，方便下次训练：

第四步，进行预测：

主要代码（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('./captcha/0hwn.jpg').convert('L')        #要预测的验证码图片位置
 #     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")   #训练好模型文件的位置
         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)

查看结果：

参考链接：

https://xianzhi.aliyun.com/forum/topic/1470/

https://xianzhi.aliyun.com/forum/topic/1505/

https://xianzhi.aliyun.com/forum/topic/1552/

https://cloud.tencent.com/developer/labs/lab/10325