验证码&游戏外挂与图像识别——ANN
2008-07-02 16:56
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前面一篇写了关于简单的字符分离和特征提取,实际上,如果仅仅写个记牌器,那上篇识别出的特征直接用作牌面识别即可,根本无需进一步的工作——利用人工神经网络识别,但毕竟是为了完成前面的网页文章,还是写一下这个网络,因为验证码经处理后,可不会那么“老实”的每次都一模一样,我们需要的是神经网络来识别这些家伙。
从面向对象角度来说,人工神经网络可以向下划分为层,而层是由神经元构成的——神经元是构成人工神经网络的最基本单位,我们应该先实现它。神经元需要接受输入,无论它位于输入层、中间层或是输出层,同样也需要有输出,对于每一个输入,都需要对应一个权值,为了判断这个神经元处于激活还是抑制状态,我们需要一个函数来处理输入从而得到输出——这,就是一个神经元,据此,写出其代码:
从面向对象角度来说,人工神经网络可以向下划分为层,而层是由神经元构成的——神经元是构成人工神经网络的最基本单位,我们应该先实现它。神经元需要接受输入,无论它位于输入层、中间层或是输出层,同样也需要有输出,对于每一个输入,都需要对应一个权值,为了判断这个神经元处于激活还是抑制状态,我们需要一个函数来处理输入从而得到输出——这,就是一个神经元,据此,写出其代码:
Public Class Neuron '输入个数 Protected m_inputsCount As Integer = 1 '权值 Protected weights As Double() = New Double(0) {} '激励函数 Protected [function] As IActivationFunction = New SigmoidFunction() ' 加权的输入和 Protected sum As Double ' 神经输出值 Protected m_output As Double '随机数发生器 Protected Shared rand As New Random() ' 输入总数属性 Public Property InputsCount() As Integer Get Return m_inputsCount End Get Set(ByVal value As Integer) m_inputsCount = Math.Max(1, value) weights = New Double(m_inputsCount - 1) {} End Set End Property ' 激活函数 Public Property ActivationFunction() As IActivationFunction Get Return [function] End Get Set(ByVal value As IActivationFunction) [function] = value End Set End Property ' 输出值 Public ReadOnly Property Output() As Double Get Return m_output End Get End Property ' 设置—获取权 Default Public Property Item(ByVal index As Integer) As Double Get Return weights(index) End Get Set(ByVal value As Double) weights(index) = value End Set End Property ' 创建 Public Sub New() End Sub Public Sub New(ByVal inputs As Integer) Me.New(inputs, New SigmoidFunction()) End Sub Public Sub New(ByVal inputs As Integer, ByVal [function] As IActivationFunction) Me.[function] = [function] InputsCount = inputs End Sub ' 计算神经输出值 Public Function Compute(ByVal input As Double()) As Double If input.Length <> m_inputsCount Then Throw New ArgumentException() End If sum = 0.0 For i As Integer = 0 To m_inputsCount - 1 ' 计算输入值加权和 sum += weights(i) * input(i) Next m_output = [function].Output(sum) Return m_output End Function ' 随机权值 Public Sub Randomize() For i As Integer = 0 To m_inputsCount - 1 weights(i) = (rand.NextDouble()) Next End Sub End Class
这就是一个神经元了。需要解释的是,我们用的S型函数是通过一个接口IActivationFunction来达到“传递”目的的。该接口的
''' <summary> ''' 激励函数 —— 接口 ''' </summary> Public Interface IActivationFunction ' 计算函数值 Function Output(ByVal input As Double) As Double ' 计算函数值微分 Function OutputPrime(ByVal input As Double) As Double ' 计算函数值微分 ' 使用函数值作为输入 Function OutputPrime2(ByVal input As Double) As Double End Interface
接下来实现它们即可。
由神经元来构成层,实际上,从某种意义来说,层,也是一个神经,它们的代码极其相似,工作原理也基本相同:
Public Class Layer ' 输入个数 Protected m_inputsCount As Integer '神经元个数 Protected m_neuronsCount As Integer '层激励函数 Protected [function] As IActivationFunction '神经 Protected neurons As Neuron() '输出 Protected m_output As Double() ' 输入个数 Public Property InputsCount() As Integer Get Return m_inputsCount End Get Set(ByVal value As Integer) m_inputsCount = Math.Max(1, value) InitLayer() End Set End Property ' 神经个数 Public Property NeuronsCount() As Integer Get Return m_neuronsCount End Get Set(ByVal value As Integer) m_neuronsCount = Math.Max(1, value) InitLayer() End Set End Property ' 激励函数 Public Property ActivationFunction() As IActivationFunction Get Return [function] End Get Set(ByVal value As IActivationFunction) [function] = value For i As Integer = 0 To m_neuronsCount - 1 neurons(i).ActivationFunction = value Next End Set End Property ' 获取指定神经元 Default Public ReadOnly Property Item(ByVal index As Integer) As Neuron Get Return neurons(index) End Get End Property ' 获取层输出 Public ReadOnly Property Output() As Double() Get Return m_output End Get End Property ' 创建 Public Sub New() Me.New(1, 1, New SigmoidFunction()) End Sub Public Sub New(ByVal neuronsCount As Integer) Me.New(neuronsCount, 1, New SigmoidFunction()) End Sub Public Sub New(ByVal neuronsCount As Integer, ByVal inputsCount As Integer) Me.New(neuronsCount, inputsCount, New SigmoidFunction()) End Sub Public Sub New(ByVal neuronsCount As Integer, ByVal inputsCount As Integer, ByVal [function] As IActivationFunction) Me.m_inputsCount = Math.Max(1, inputsCount) Me.m_neuronsCount = Math.Max(1, neuronsCount) Me.[function] = [function] InitLayer() End Sub ' 计算层输出 Public Function Compute(ByVal input As Double()) As Double() For i As Integer = 0 To m_neuronsCount - 1 m_output(i) = neurons(i).Compute(input) Next Return m_output End Function ' 随机化该层 Public Sub Randomize() For Each neuron As Neuron In neurons neuron.Randomize() Next End Sub ' 初始化层 Private Sub InitLayer() ' 创建层 neurons = New Neuron(m_neuronsCount - 1) {} For i As Integer = 0 To m_neuronsCount - 1 neurons(i) = New Neuron(m_inputsCount, [function]) Next ' 分配输出数组 m_output = New Double(m_neuronsCount - 1) {} End Sub End Class
只是层里面的激励函数我们另外实现,当然,用S型函数也不是不可以。。。。
接下来就是由层构成网络,还是上面那句话,网络啊,工作原理也和神经有点类似,代码基本是重复的罗列:
''' <summary> ''' 网络——神经层的集合 ''' </summary> <System.Serializable()> Public Class Network ' 输入个数 Protected inputsCount As Integer '层数 Protected m_layersCount As Integer '输出 Protected m_output As Double() '层 Protected layers As Layer()
' 层数 Public ReadOnly Property LayersCount() As Integer Get Return m_layersCount End Get End Property ' 获取指定层 Default Public ReadOnly Property Item(ByVal index As Integer) As Layer Get Return layers(index) End Get End Property ' 获取输出 Public ReadOnly Property Output() As Double() Get Return m_output End Get End Property Sub New() End Sub ' Constructors Public Sub New(ByVal inputsCount As Integer, ByVal ParamArray neuronsCountPerLayer As Integer()) Me.New(New SigmoidFunction(), inputsCount, neuronsCountPerLayer) End Sub Public Sub New(ByVal [function] As IActivationFunction, ByVal inputsCount As Integer, ByVal ParamArray neuronsCountPerLayer As Integer()) Me.inputsCount = Math.Max(1, inputsCount) Me.m_layersCount = neuronsCountPerLayer.Length ' 创建层集合 layers = New Layer(m_layersCount - 1) {} For i As Integer = 0 To m_layersCount - 1 Dim m As Integer = 0 If i = 0 Then m = inputsCount Else m = neuronsCountPerLayer(i - 1) layers(i) = New Layer(neuronsCountPerLayer(i), m, [function]) Next End Sub
' 计算输出 Public Function Compute(ByVal input As Double()) As Double() m_output = input For i As Integer = 0 To m_layersCount - 1 m_output = layers(i).Compute(m_output) Next Return m_output End Function
' 随机化网络 Public Sub Randomize() For Each layer As Layer In layers layer.Randomize() Next End Sub
End Class
如此,就构成了这个神经网络。。。。。。
具体应用呢,我们需要另外定义一些属性、方法,来实现Back Propagation Learning:
属性:
1、学习速率
2、精度
3、动量
方法:
1、学习
2、计算误差
3、更新数据(各层权值直至各神经权值)
代码就是一些循环,不贴了。
有一点需要注意的,就是从图像中提取适当个数的特征可以加速学习和识别速度,但是太少就会影响网络的判断能力。
结合前面例子,我们可以提取垂直投影特征,来解决那些最幼稚的验证码:)有兴趣的话可以实现下。
一下是针对某网站的验证码图片处理后得到的一组学习图片采用随机特征提取后(图片大小14*18,提取特征40个,学习精度0.01),进行学习的数据:
学习次数 误差 Now.Second(当前时间的秒)
100 1.74766228723842 49 200 1.33293174843217 49 300 1.21399094064815 49 400 1.15740689778003 49 500 1.12433264177344 49 600 1.10263310876503 50 700 1.08728586760529 50 800 1.07582728337775 50 900 1.06688719120981 50 1000 1.05958542167266 50 1100 1.05308338562932 51 1200 1.04373940177007 51 1247 0.997537607633144 51 1300 0.608558811884911 51 1400 0.304230610883604 51 1500 0.212165790693552 51 1600 0.165892333507009 51 1700 0.138465048204805 52 1800 0.120396685718836 52 1900 0.107594382540998 52 1978 0.099921549727966 52
从上面数据可以看出,如果特征提取位置较好(这里是随机生成),则学习速度很快,几秒时间即可学习完成。
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